CN111446623A - Three-end type S-shaped annular quantum cascade laser - Google Patents

Abstract

The invention discloses a three-terminal S-shaped annular quantum cascade laser. The laser comprises a substrate, a collector electrode, a quantum cascade structure layer, a quantum energy level matching layer, a base electrode and an emitter electrode, which are arranged in sequence from bottom to top. There are steps arranged between the emitter and the base, and between the quantum cascade structure layer and the collector; the laser also includes a collector electrode arranged on the top of the collector or under the substrate, and a base arranged on the top of the base. Electrode, the emitter electrode arranged on the top of the emitter. The laser is also etched with an S-shaped ring waveguide and a bar-shaped straight waveguide coupled with the S-shaped ring waveguide, and the bar-shaped straight waveguide includes an input section and a coupling section. The three-terminal S-type ring quantum cascade laser has simple design, good tunability, multi-wavelength or broad-spectrum or chaotic laser or frequency comb output, and can effectively reduce mid-infrared and terahertz applications in a wide range of mid-infrared and terahertz applications. The application cost of the source.

Description

A three-terminal S-type ring quantum cascade laser

technical field

The invention belongs to the technical field of semiconductor lasers, and in particular relates to a three-terminal S-shaped annular quantum cascade laser.

Background technique

Compared with the carrier conduction band-valence band stimulated emission transfer mechanism of traditional quantum well lasers, Quantum Cascade Lasers (QCLs) have a unique carrier conduction band transfer cascade mechanism between sub-bands. Instead, it can directly generate mid-infrared and terahertz output. Compared with the existing generation methods of mid-infrared and terahertz output, such as photoconductive mixing method, semiconductor built-in electric field method, optical rectification method, electro-optical sampling method, etc., the mid-infrared and terahertz output structure based on QCLs has higher conversion efficiency. High performance, simple cavity structure, good on-chip integration, etc., are widely used in many civil and military applications including DNA detection, biological tissue imaging, non-contact testing, public safety monitoring, gas composition detection, and THz wireless communication. . In order to improve the versatility of QCLs in different applications and reduce the application cost, the mid-infrared or terahertz output of QCLs is required to have better tunable characteristics, or to have multi-wavelength or broad-spectrum output characteristics.

In order to improve the tunable characteristics of QCLs, the current mainstream methods include: external cavity grating tuning method, strong magnetic field method, distributed feedback structure method, sampling grating reflector (SGR) method, etc. However, these methods are too complicated, have low stability and high energy consumption, and are not suitable for future low-power, miniaturized on-chip integrated applications.

In order to obtain the mid-infrared or terahertz output of multi-wavelength or broad-spectrum QCLs, the main method is to design the active region of the quantum cascade structure of QCLs, so that the upper subband-lower subband energy state transfer of the active region is achieved. It is single-energy state-dual-energy state, single-energy state-continuous state, continuous state-continuous state, QCL multi-core and multi-stack structure, etc., but these methods require complex optimization design of the corresponding active area, which has a huge workload. Shortcomings such as long device design cycle.

Under the condition of a certain external light injection signal, the laser can generate a noise-like wide-spectrum random output whose intensity, frequency and phase change rapidly in a limited range, that is, chaotic laser. In recent years, chaotic lasers have been widely researched and applied in the fields of secure optical communication, laser ranging, and fiber breakpoint detection.

A frequency comb is a coherent radiation generated by a laser light source, and its spectrum is composed of multiple modes that are completely equally spaced and have a clear phase relationship with each other. field. At present, the application of frequency combs has gradually extended from the far-ultraviolet band to the mid-infrared and terahertz bands. In the mid-infrared band, frequency combs can be widely used in environmental perception, gas composition detection and other fields; in the terahertz band, frequency combs can also be used in non-invasive imaging, wireless communication, and public safety monitoring. Frequency combs have great application value in many military and civilian applications.

At present, for a wide range of applications in the mid-infrared and terahertz fields, there is a lack of a device with a simple design, good tunability, and a quantum cascade structure that can output multiple wavelengths or broad spectrum or frequency comb or chaotic lasers and its applications.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the above problems, and to provide a three-terminal S-type ring quantum cascade laser, which has simple design, good tunable characteristics, multi-wavelength or wide-spectrum or chaotic Laser or frequency comb output, and can effectively reduce the application cost of mid-infrared and terahertz sources for a wide range of mid-infrared and terahertz applications.

In order to solve the above-mentioned technical problems, the technical scheme of the present invention is: a three-terminal S-type annular quantum cascade laser, the laser comprises a substrate, a collector, a quantum cascade structure layer, a quantum energy level arranged in sequence from bottom to top a matching layer, a base electrode, and an emitter electrode, there are steps arranged between the collector electrode and the quantum cascade structure layer, and between the base electrode and the emitter electrode;

The three-terminal S-type annular quantum cascade laser also includes a collector electrode arranged on the top of the collector or below the substrate, a base electrode arranged on the top of the base, and an emitter electrode arranged on the top of the emitter;

The laser is also etched with an S-shaped annular waveguide and a strip-shaped straight waveguide coupled with the S-shaped annular waveguide, and the etching depth of the S-shaped annular waveguide and the strip-shaped straight waveguide is from the top of the emitter to the top of the base, Any depth at the top of the quantum energy level matching layer, the top of the quantum cascade structure layer or the top of the collector, wherein at least one side of the S-shaped ring waveguide in the annular region or outside the annular region is etched to a depth only from the top of the emitter to the base top, the strip-shaped straight waveguide includes an input section and a coupling section;

The quantum cascade structure layer is formed by stacking at least two QCL stack units with the same structure in series, and the QCL stack unit includes at least two QCL subunits with the same structure, each of which is composed of an active region. and an implanted region, the implanted region includes several sections of doped regions, and at least one section of the doped regions has different doping concentration parameters between the different types of QCL subunits.

The quantum cascade structure layer includes N QCL stacking units: the first QCL stacking unit AB, the ith QCL stacking unit AB, the Nth QCL stacking unit AB, or the first QCL stacking unit ABB, the ith QCL stacking unit AB QCL stack unit ABB, Nth QCL stack unit ABB, wherein i, N are integers greater than 1, i≤N.

It is worth noting that the structural composition of the S-shaped ring waveguide and the strip-shaped straight waveguide can be controlled by controlling the corresponding etching depth. The waveguide, that is, the S-shaped ring waveguide and the strip-shaped straight waveguide structure only contains the emitter, and can also be etched from the top of the emitter to the top of the base, the top of the quantum energy level matching layer, the top of the quantum cascade structure layer or the top of the collector. S-shaped ring waveguide and straight strip waveguide, if etched from the top of the emitter to the top of the collector is an S-shaped ring waveguide and a straight strip waveguide, the structure of the S-shaped ring waveguide and the straight strip waveguide includes the emitter and the base. , quantum energy level matching layer, and quantum cascade structure layer. In particular, in order to maintain the characteristics of using a three-terminal transistor, it must be required that at least one side of the S-shaped ring waveguide circular area or the area outside the circular area is etched only to the top of the base region.

Further, the waveguide structure only contains the emitter type, the cavity structure of the quantum cascade structure layer of the device is mainly F-P type, and the S-type ring waveguide structure will fine-tune the mode distribution and traveling wave mode in the F-P cavity of the device. When the S-shaped ring waveguide structure includes an emitter, a base, a quantum energy level matching layer, and a quantum cascade structure layer, the resonant cavity structure of the quantum cascade structure layer of the whole device is completely changed to a ring resonator cavity, and the mode distribution and line The wave pattern is completely distributed according to the device characteristics of the ring resonator. That is to say, the depth of etching determines the cavity resonance characteristics of the device. With the increase of etching depth, the cavity resonance gradually changes from the F-P type resonance characteristics to the ring resonance cavity resonance characteristics.

The three-terminal S-shaped ring quantum cascade laser using the S-shaped ring waveguide structure can use the strong third-order nonlinearity of the ring structure to obtain the cascade-enhanced four-wave mixing effect, which is very beneficial to the different tooth comb modes of the output frequency comb. The uniformity of the spacing is locked with relative phase, resulting in a frequency comb with excellent performance. In addition, the traveling wave mode of the S-shaped ring waveguide structure laser and the asymmetric ring waveguide structure of the S-shaped ring waveguide can avoid the spatial hole burning effect caused by the standing wave mode of the ordinary Fabry-Perot (F-P) structure laser. , which will further stabilize and improve the characteristics of the obtained high-performance frequency comb.

In the above technical solution, preferably, each QCL subunit has only one section of doping region, and the doping concentration parameters of the doping region between different types of QCL subunits are different. Preferably, at least one of the QCL subunits includes two or more doped regions, and the QCL subunit has at least one doped region whose doping concentration parameters are different from those of other doped regions. Doping concentration parameter. Further preferably, each of the QCL stack unit structures includes only two types of the QCL subunits, each QCL subunit has only a section of doping region, and the doping concentration parameters of the doping regions of the two QCL subunits are different. . More preferably, each of the QCL stack unit structures includes only two types of QCL subunits, each of the QCL subunits includes only two sections of doping regions with different doping concentration parameters, and the two types of the QCL subunits only include two sections of doped regions with different doping concentration parameters. The doping concentration parameters of at least one segment of the doped regions are different from the doping concentration parameters of the other segment doped regions.

It should be noted that the doping concentration parameter of each doped region is unique, that is, there are no two doping concentration parameters in the same doped region. In addition, sometimes for the convenience of comparison, the same segment of the same doped region may be further subdivided into multi-segment regions, but the doping concentrations of the subdivided multi-segment regions are the same. In addition, different kinds of QCL subunits only have different doping concentration parameters, and other parameters including the layer thickness sequence, layer material composition sequence, and layer doping position of the subunit structure are all the same.

In the above technical solution, the active region of the QCL subunit adopts a U state-L state transition design, and the U state and the L state are any one of a single-energy state, a multi-energy state or a continuous state, so the The multi-energy state includes at least two energy states. The working or lasing wavelength corresponding to the active region of the QCL subunit is in the mid-infrared or terahertz band.

It is worth noting that the quantum cascade structure layer in the present invention can also be applied to the existing periodic subunit structure whose active region is mid-infrared and terahertz output, that is, the QCL subunit structure is not limited to the structure provided by the present invention. , the existing periodic sub-structure units that have been designed and can work can be used as "QCL sub-units" in the quantum cascade structure layer of the present invention, and are constructed into corresponding quantum cascade structure layers. Under the guidance of the idea of the present invention, any quantum cascade structure layer constructed by using other existing periodic sub-structural units is within the protection scope of the present invention.

In the above technical solution, the three-terminal S-type ring quantum cascade laser is a multi-pole device with a QCL stack unit as an active region, and "multi-pole" refers to a multi-pole device that is perpendicular to the growth direction of the quantum cascade structure layer. There are end-face electrodes, and the multi-pole structure includes at least three types of electrode structures: emitter, base, and collector.

In the above technical scheme, for the three-terminal S-type ring quantum cascade laser structure with a common collector, it is preferable to set several insulating layers on the S-type ring waveguide and the base to make the laser form a multi-segment structure with several segments. Control subunit. It is worth noting that the three-terminal S-type ring quantum cascade laser can also be used as a sub-unit to etch the aforementioned devices on the same device (as shown in Figure 5 and Figure 6 or Figure 8 and Figure 9) As an array structure of subunits, the array structure can be a chain or square array. Different independent electrodes of different array units are insulated from each other, and different array units are coupled through waveguides, which can be used to explore further applications.

Further, there are at least one collector electrode, at least one base electrode, and at least one emitter electrode in the three-terminal S-type ring quantum cascade laser. There can also be multiple electrodes of the same type on the same segment of the control subunit. A collector electrode can be grown on the top of the collector layer on the left and right sides of the quantum cascade structure layer, although the spatial positions of the two collector electrodes are different, but The roles in the device are all the same and can be attributed to the "collector electrode" type of electrode. Similarly, if the space location allows, a base electrode can also be grown on the top of the base layer on the left and right sides of the emitter layer, and both base electrodes are classified as "base electrodes".

In the three-terminal S-type ring quantum cascade laser with multi-segment control subunits, each segment of the control subunit includes at least three types of electrode structures: emitter, base, and collector. In particular, the base-emitter bias ( _Vbe ) controls the current density injected into the quantum cascade layer in the control subunit, and the base-collector bias ( _Vbc ) controls the quantum flow in the control subunit Device bias for cascaded layers. Each electrode in each type of electrode structure can be controlled by an independent segment voltage, and the value of the independent segment voltage can be any one of positive voltage, zero voltage and negative voltage. Different combinations of the values are performed, and the output characteristics of the output of the multi-segment quantum cascade structure layer in the time domain or the wavelength domain are controlled according to the different independent segment voltage combinations. The multi-segment control structure is mainly to control the work output of each subunit separately, and further combine the characteristics of the laser to carry out corresponding applications, such as frequency comb, ultrafast mode locking, optical switching characteristics, etc.

In the above technical solution, under the applied combination of the V _be and the V _bc device bias, at least one of the QCL sub-units in each of the QCL stack units can work or lasing. Further preferably, under the applied combination of the V _be and the V _bc device bias, at least two of the QCL stack units can work or lasing, and in each of the working or lasing QCL stack units At least one of the QCL subunits is capable of working or lasing.

In the above technical solution, under a specific combination of the applied V _be and the V _bc device bias voltage, at least one of the QCL sub-units in each of the QCL stack units can work or lasing. Further preferably, under the specific applied combination of the V _be and the V _bc device bias, at least two of the QCL stack units can work or lasing at the same time, and each of the working or lasing QCL stack units At least one of the QCL subunits is capable of working or lasing.

In the above technical solution, when the applied combination of the V _be and the V _bc device bias voltage changes, at least one of the QCL sub-units in each of the QCL stack units can work or lasing. Further preferably, when the applied _Vbe and the _Vbc device bias are changed in combination, at least two of the QCL stack units can work or lasing at the same time, and each of the working or lasing QCL stacks At least one of the QCL subunits in the unit is capable of working or lasing.

In the above technical solution, when the applied combination of the V _be and the V _bc device bias voltage changes, at least one of the QCL sub-units in each of the QCL stack units can work or lasing, work or lasing. The output wavelength varies with the applied device bias. Preferably, when the applied combination of the V _be and the V _bc device bias voltage changes, at least two of the QCL stack units can work or lasing at the same time, and in each of the working or lasing QCL stack units At least one of the QCL sub-units is capable of operating or lasing, and the operating or lasing output wavelength varies with the applied combination of the _Vbe and the _Vbc device bias. Further preferably, when the applied combination of the V _be and the V _bc device bias voltage changes, at least two of the QCL sub-units in each of the QCL stack units can work or lasing, work or stimulate simultaneously. The emission output wavelength varies with the applied combination of the _Vbe and the _Vbc device bias. More preferably, when the applied combination of the V _be and the V _bc device bias voltage changes, at least two of the QCL stack units can work or lasing simultaneously, and each of the working or lasing QCL stack units At least two of the QCL subunits are capable of operating or lasing simultaneously, and the operating or lasing output wavelength varies with the applied combination of the _Vbe and the _Vbc device bias.

The working or lasing outputs are superimposed into a multi-wavelength output or a broad spectrum output or a frequency comb output. Further, the working or lasing output is superimposed into a multi-wavelength output or a broad-spectrum output or a frequency comb output, and the multi-wavelength output or the broad-spectrum output or the frequency comb output varies with the applied V _be and V _bc . device bias combination changes.

In the above technical solution, when an external optical signal is injected into the input section of the straight strip waveguide, the externally injected signal can interact with the signal in the S-shaped ring waveguide structure through the coupling section of the straight strip waveguide, affecting the S-shaped straight waveguide. The phase or mode of the signal in the ring waveguide structure is locked, thereby changing the output characteristics of the three-terminal S-type ring quantum cascade laser. In particular, the injection of an external optical signal enables the three-terminal S-type ring quantum cascade laser to be formed in the wavelength range of the tunable multi-wavelength output or broad-spectrum output capable of generating limited intensity, frequency and phase A chaotic laser with a noise-like wide-spectrum random output in a rapidly changing interval, the chaotic laser output changes with the change of the injected external optical signal or with the change of the applied combination of the V _be and the V _bc device bias voltage .

The three-terminal S-type annular quantum cascade laser provided by the present invention has the following beneficial effects:

1. The quantum cascade structure in the three-terminal S-type ring quantum cascade laser, by stacking at least two QCL stack units in series, utilizes at least two different doping concentration parameters contained in each QCL stack unit The QCL subunit, or at least one QCL subunit included in each QCL stack unit works or lasing at different wavelengths, which increases the output spectral window of the applied device;

2. The quantum cascade structure layer in the three-terminal S-type ring quantum cascade laser can also be applied to the existing periodic subunit structure whose active region is mid-infrared and terahertz output, which can effectively simplify the device structure design. high adaptability;

3. When the combination of the V _be and the V _bc device bias applied by the three-terminal S-type ring quantum cascade laser changes, the obtained spectral output can vary with the applied V _be and the V The _bc device bias combination changes, or when the device is biased under the applied combination of the V _be and the V _bc device bias, the spectral output is relatively stable;

4. The three-terminal S-type ring quantum cascade laser can be further used in time-domain or frequency-domain spectral characteristic applications of QCLs, such as optical frequency comb output, mid-infrared chaotic laser output, mode-locked mid-infrared, terahertz output, Multi-wavelength multiplexing of mid-infrared and terahertz sources, etc.

Description of drawings

Fig. 1 is a schematic diagram of two arrangement structures of quantum cascade structure layers in the present invention; Fig. 1(a): QCL stack units are all AB stacks; Fig. 1(b): QCL stack units are all ABB stacks.

FIG. 2 is a schematic diagram of parameters of two QCL subunits A and B of the quantum cascade structure layer in the present invention.

Fig. 3 is a schematic diagram of a QCL subunit with at least one doping concentration parameter of the quantum cascade structure layer in the present invention; Fig. 3(a): A type QCL subunit doping concentration parameter is N _d,1 =N ₁ , N _d,2 =N ₁ , the doping concentration parameters of B type QCL subunits are N _d,1 =N ₁ ,N _d,2 =N ₂ (N ₁ ≠N ₂ ); Figure 3(b): A type QCL The subunit doping concentration parameter is N _d,1 =N ₁ , N _d,2 =N ₂ (N ₁ ≠N ₂ ), and the B type QCL subunit doping concentration parameter is N _d,1 =N ₁ ,N _{d , 2} =N ₃ (N ₃ ≠N ₂ ).

FIG. 4 is a schematic diagram of the electric field in a QCL stack unit in the quantum cascade structure layer of the present invention.

FIG. 5 is a schematic structural diagram of the three-terminal S-type ring quantum cascade laser in Example 3. FIG.

FIG. 6 is a top view of the three-terminal S-type ring quantum cascade laser in Example 3. FIG.

FIG. 7 is a schematic diagram of the energy band of the three-terminal S-type ring quantum cascade laser in Example 3. FIG.

8 is a schematic structural diagram of another three-terminal S-type ring quantum cascade laser of Embodiment 3;

9 is a top view of a three-terminal S-type annular quantum cascade laser of another mode of Embodiment 3;

FIG. 10 is a schematic diagram of the wide gain spectrum corresponding to the three-terminal S-type ring quantum cascade laser in Example 3. FIG.

Figure 11 is a schematic diagram of two tunable wide-gain spectra corresponding to the three-terminal S-type ring quantum cascade laser in Example 3; Figure 11(a): the base-emitter voltage V _be = V ₁ The electrode-base voltage is changed from V ₂ to V _2' ; Figure 11(b): The base-emitter voltage V ₁ is changed from V 1' to V _1' , and the collector-base voltage V _cb =V ₂ remains unchanged.

Figure 12 is a schematic diagram of two tunable gain spectra corresponding to the three-terminal S-type ring quantum cascade laser in Example 3; Figure 12(a): V _be = V ₁ unchanged, collector-base voltage V _cb The gain spectrum of the device at V _2" , V _2' and V ₂ , respectively; Fig. 12(b): V _cb = V ₂ unchanged, the base-emitter voltage V _be is V _1" , V _1' and V The device gain spectrum at ₁ .

13 is a schematic structural diagram of a three-terminal S-type ring quantum cascade laser in Example 4;

14 is a top view of the three-terminal S-type annular quantum cascade laser in Example 4;

15 is a schematic structural diagram of another three-terminal S-type ring quantum cascade laser of Embodiment 4;

16 is a top view of the three-terminal S-type ring quantum cascade laser of another mode of Embodiment 4;

Figure 17 is a schematic diagram of two broad gain spectra corresponding to the three-terminal S-type ring quantum cascade laser in Example 4; Figure 17(a): V _be1 =V ₁ , V _be2 =V ₁ , V _be3 =V ₁ , V _cb1 =V ₂ , V _cb2 =V _2′ , V _cb3 =V _{2 ″} ; Figure 17(b): V _cb1 =V ₂ , V _cb2 =V ₂ , V _cb3 =V ₂ , Gain spectrum in the case of V _be1 =V ₁ , V _be2 =V _1' , V _be3 =V _1" .

Figure 18 is a schematic diagram of two tunable wide gain spectra corresponding to the three-terminal S-type ring quantum cascade laser in Example 4; Figure 18(a) V _be1 =V ₁ , V _be2 =V ₁ , V _be3 =V _1. The collector-base bias voltages of the first, second and third control sections are changed from V ₂ to V ₃ , V _2' to V _3' , V _2" to V _3" , respectively, That is, V _cb1 =V ₃ , V _cb2 =V _3' , V _cb3 =V _3" , the schematic diagram of gain spectrum change; Fig. 18(b) V _cb1 =V ₂ , V _cb2 =V ₂ , V _cb3 =V ₂ , The base-emitter bias voltages of the first, second and third control segments are changed from V ₁ to V ₃ , V _1' to V _3' , and V _1" to V _3" respectively, that is, V A schematic diagram of the change of the gain spectrum when _be1 =V ₃ , V _be2 =V _3' , and V _be3 =V _3" .

Fig. 19 is a schematic diagram of two kinds of ultra-broad gain spectra corresponding to the three-terminal S-type ring quantum cascade laser in Example 4; Fig. 19(a) V _be1 =V ₁ , V _be2 =V ₁ , V _be3 =V ₁ , V _cb1 =V ₂ , V _cb2 =V _2' , V _cb3 =V _{2 "} in the case of super-broad spectrum superposition schematic diagram; Figure 19(b) V _cb1 =V ₂ , V _cb2 =V ₂ , V _cb3 =V ₂ , V _be1 =V ₁ , V _be2 =V _1' , V _be3 =V _1" . Schematic diagram of ultrabroad spectrum stacking in the case.

Fig. 20 is a frequency domain output power distribution diagram of the frequency comb output corresponding to the three-terminal S-type ring quantum cascade laser in Example 4.

DESCRIPTION OF REFERENCE NUMERALS: 1. The first QCL stack unit AB; 2. The i-th QCL stack unit AB; 3. The N-th QCL stack unit AB; 4. The first QCL stack unit ABB; QCL stack unit ABB; 6, Nth QCL stack unit ABB; 7, substrate; 8, collector; 9, quantum cascade structure layer; 10, quantum level matching layer; 11, base; 12, emitter 13, collector electrode; 14, base electrode; 15, emitter electrode; 16, coupling section; 17, input section; 18, strip straight waveguide; 19, S-shaped ring waveguide;

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be pointed out that the directional terms and sequence terms mentioned in the following embodiments, such as "up", "down", "front", "rear", "left", "right", etc., are only for reference to the accompanying drawings. Directions, therefore, the directional terms used are illustrative and not limiting of the invention.

The three-terminal S-type annular quantum cascade laser of the present invention comprises a substrate 7, a collector electrode 8, a quantum cascade structure layer 9, a quantum energy level matching layer 10, a base electrode 11, an emission The electrode 12, between the collector electrode 8 and the quantum cascade structure layer 9, and between the base electrode 11 and the emitter electrode 12 are all arranged in steps. The stepped arrangement is provided for laying the collector electrode 13, the base electrode 14, and the emitter electrode 15.

The three-terminal S-type ring quantum cascade laser further includes a collector electrode 13 arranged on the collector electrode 8 or below the substrate 7 , a base electrode 14 arranged on the base electrode 11 , and an emitter electrode arranged on the emitter electrode 12 . electrode 15.

The laser is also etched with an S-shaped ring waveguide 19 and a bar-shaped straight waveguide 18 coupled with the S-shaped ring waveguide 19. The etching depth of the S-shaped ring waveguide 19 and the bar-shaped straight waveguide 18 is from the top of the emitter to the base electrode 11. Any depth of the top, the top of the quantum level matching layer 10, the top of the quantum cascade structure layer 9 or the top of the collector 8, wherein, at least one side of the annular region of the S-shaped annular waveguide 19 or outside the annular region has an etching depth of only From the top of the emitter to the top of the base, the strip-shaped straight waveguide 18 includes an input section 17 and a coupling section 16;

As shown in FIG. 1, the quantum cascade structure layer 9 in the three-terminal S-type ring quantum cascade laser of the present invention is formed by stacking at least two QCL stack units with the same structure in series. The unit includes at least two QCL subunits with the same structure. Each QCL subunit consists of an active area and an implantation area. The implantation area includes several sections of doped regions. The doping concentration parameters are different.

In order to make the quantum cascade structure layer 9 in the three-terminal S-type ring quantum cascade laser of the present invention easier to understand, the following example is carried out by taking Embodiment 1 and Embodiment 2 that each QCL stack unit includes two kinds of QCL subunits. Detailed description:

Example 1

As shown in FIG. 1 , two schematic diagrams of the arrangement of the quantum cascade structure layer 9 in this embodiment, wherein the QCL stack units in FIG. 1( a ) are all AB stacks, including the first QCL stack unit AB1 , the second The i QCL stack units AB2; the Nth QCL stack unit AB3, the quantum cascade structure layer 9 is formed by superposing the N aforementioned QCL stack units to form an AB/.../AB/.../AB stack structure. The QCL stack units in Fig. 1(b) are all ABB stacks, including the first QCL stack unit ABB4, the i-th QCL stack unit ABB5, and the N-th QCL stack unit ABB6. The quantum cascade structure layer 9 is composed of N above-mentioned QCL stacking units are superimposed to form an ABB/…/ABB/…/ABB stack structure.

Each QCL stack unit in Fig. 1(a) and Fig. 1(b) only contains two kinds of QCL subunits, A and B. The two kinds of QCL subunits, A and B, are composed of an active area and an injection area, and the injection area is only Contains a section of doped region. Among them, the doping concentration parameter N _{d,1 of the A-type QCL subunit, and the doping concentration parameter N d,2 of} the B-type QCL subunit, (N _d,1 ≠N _d,2 ). It should be noted that the doping concentration parameter of the A-type QCL subunit may be greater than or smaller than the doping concentration parameter of the B-type QCL subunit, as long as the doping concentration parameters are different. In this embodiment, the A-type QCL subunit The cell doping concentration parameter N _d,1 is greater than the B-type QCL subunit doping concentration parameter N _d,2 . As shown in Figure 2, the two QCL subunits A and B are the same in other parameters except for the doping concentration parameter. The other parameters here include: the layer thickness sequence of the QCL subunit, the layer material composition sequence, Parameters such as layer doping positions are conventionally known in the art. Specifically, in this embodiment, the lengths of the two QCL subunits A and B are both L _p , the lengths of the active regions are both L _a , the lengths of the implanted regions are both L _p -L _a , and the doping positions are both L _d,l to L _d,r , the doping lengths are all L _d .

In Fig. 1(a) and Fig. 1(b), electrons are injected from the first QCL stack unit, and then enter the second, ..., ith, ..., and Nth QCL stack units in sequence. Among them, in each QCL stack unit in Figure 1(a), electrons are injected from the A-type QCL subunit, and then enter the B-type QCL subunit of the QCL stack unit; in each QCL stack unit in Figure 1(b), Electrons are injected from the A-type QCL sub-cell, then into the first B-type QCL sub-cell of the QCL stack cell, and then into the second B-type QCL sub-cell of the QCL stack cell.

In each QCL subunit, electrons are injected from the injection region, and after electron-electron and electron-phonon scattering, tunnel into the active region; in the active region, the electrons at the upper lasing level are stimulated to radiate out A photon transitions down to the lower lasing energy level; then, the electron quickly enters the carrier depletion energy level after electron-phonon scattering, and then enters the next QCL through electron-electron and electron-phonon scattering coupling The energy level of the implanted region of the subunit.

As shown in FIG. 4 , a schematic diagram of the electric field of the quantum cascade structure layer 9 of the present embodiment when current is injected, wherein the frame is a schematic diagram of the electric field of the i-th QCL stack unit, and the corresponding structure is shown in FIG. 1( b ) ABB/…/ABB/…/ABB stack structure in . For convenience of description, the QCL stack unit ABB in FIG. 1(b) is marked as three QCL subunits A, B1, and B2 from top to bottom. From left to right in the box are the corresponding electric fields of the three QCL subunits B2, B1, and A, respectively. Among them, L represents the length of the ith QCL stack unit, L _d represents the length of the doped region of each QCL subunit, and L _a represents the length of the active region of each QCL subunit, which is marked by a dotted rectangle.

Due to the influence of injected electrons, the net charge in the undoped region of each subunit is a negative constant, so its electric field decreases linearly. Due to the presence of positively charged ionized donor ions, the net charge of the doped region of each QCL subunit can be a positive constant, zero or a negative constant, which is taken as a positive constant, so its electric field rises linearly. In addition, here the doping concentration parameter N _d,1 of the A-type QCL subunit is greater than the B-type QCL subunit doping concentration parameter N _d,2 , so the positive net charge of the doped region of the A-type QCL subunit is greater than that of the B-type QCL subunit. The positive net charge in the doped regions of the QCL subunits further causes the electric field rising slope of the doped regions of the A-type QCL subunits to be greater than the electric field rising slope of the B-type QCL subunits doped regions. In addition, when the current density injected into the quantum cascade structure layer 9 makes the total equivalent net charge of each QCL stack unit ABB zero, due to the periodicity of the ABB/.../ABB/.../ABB stack structure, the quantum cascade The electric field of the structural layer 9 will exhibit periodic changes.

It should be noted that the present invention does not have any special limitation on the specific length value of the QCL subunit, and can be designed according to actual requirements. Likewise, there is no particular limitation on the doping concentration parameter. In special cases, the doping concentration parameters of different QCL subunits in each QCL stack unit should make the net charge of each QCL stack unit about zero, and the corresponding device injection current is I above the device threshold, which is is the case of cascading lasing corresponding to each QCL stack unit, and the gain spectrum corresponds to the type curve shown in Figure 10 (taking a three-terminal S-type ring quantum cascade laser device as an example). In general, the net charge of each QCL stack unit may not be zero, so that under a specific bias voltage, only one QCL subunit in each QCL stack unit can work, and its gain spectrum is shown in Figure 12 ( Take the three-terminal S-type ring quantum cascade laser device as an example). Therefore, when the injection current I exceeds the device threshold, the net charge of each QCL stack unit should not be too large.

Example 2

As shown in FIG. 3 , in this embodiment, the QCL subunits of the quantum cascade structure layer 9 each have two-stage doped regions. In FIG. 3( a ), the doping concentration parameters of the two-stage doping regions of the A-type QCL subunit are the same, and both are N ₁ . The doping concentration parameters of the two-stage doping regions of the B-type QCL subunit are respectively N ₁ and N ₂ (N ₁ ≠N ₂ ).

In FIG. 3( b ), the A-type QCL subunit has two-stage doping regions, and the doping concentration parameters of the two-stage doping regions are N ₁ and N ₂ (N ₁ ≠N ₂ ), respectively. The B-type QCL subunit has two-stage doping regions, and the doping concentration parameters of the two-stage doping regions are N ₁ and N ₃ (N ₃ ≠N ₂ ), respectively.

Similarly, in Figure 3(a)(b), the two QCL subunits A and B are the same in other parameters except the doping concentration parameter, where other parameters include: the order of layer thickness of the QCL subunits , layer material composition sequence, layer doping position and other parameters that are conventionally known in the art. Specifically, in this embodiment, the lengths of the two QCL subunits A and B are both L _p , the lengths of the active regions are both L _a , the lengths of the implanted regions are both L _p -L _a , and the doping positions are both L _d,l to L _d,r , the doping positions of the first segment on the left are L _d,l to L _d,m , and the total doping length of the doped region is L _d,r -L _d,l .

Example 3

As shown in FIG. 5, it is a schematic diagram of the structure of the three-terminal S-type annular quantum cascade laser of the present invention. The substrate 7 and the collector 8 of the three-terminal S-type annular quantum cascade laser are sequentially arranged along the z direction from bottom to top. , quantum cascade structure layer 9 , quantum energy level matching layer 10 , base 11 and emitter 12 , the emitter 12 is etched into a strip-shaped straight waveguide 18 and an S-shaped annular waveguide 19 structure. The base electrode 11 and the emitter electrode 12 are arranged in a stepped shape, and the collector electrode 8 and the quantum cascade structure layer 9 are also arranged in a stepped shape. Further, the collector electrode 8 may contain a lower cladding layer, and the emitter electrode 12 may contain an upper cladding layer. Specifically, the layers of the device from bottom to top along the z direction are sequentially distributed as a heavy n-doped substrate 7 , an n-doped collector 8 , a quantum cascade structure layer 9 , a quantum level matching layer 10 , and a p-doped base 11 . and heavy n-doped emitter 12. A collector electrode 13 (electrode c), an emitter electrode 15 (electrode e) and a base electrode 14 (electrode b) are grown on top of the collector electrode 8, the emitter electrode 12 and the base electrode 11. Collector 8 contains a heavy n-doped lower cladding layer and emitter 12 contains a top heavy n-doped upper cladding layer.

As shown in FIG. 6 , it is a top view of the three-terminal S-type ring quantum cascade laser in FIG. 5 . The strip-shaped straight waveguide 18 includes an input section 17 and a coupling section 16 coupled with the S-shaped ring waveguide 19 . When an external optical signal is injected into the input section 17 of the straight strip waveguide 18, the externally injected signal can interact with the signal in the structure of the S-shaped ring waveguide 19 through the coupling section 16 of the straight strip waveguide 18, affecting the S-shaped ring waveguide 19 The phase or mode locking of the signal within the structure changes the output characteristics of the three-terminal S-type ring quantum cascade laser. In particular, the injection of an external optical signal enables the three-terminal S-type ring quantum cascade laser to be formed in the wavelength range of the tunable multi-wavelength output or broad-spectrum output capable of generating limited intensity, frequency and phase A chaotic laser with a noise-like wide-spectrum random output in a rapidly changing interval, the chaotic laser output varies with the injected external optical signal or with the applied base-emitter bias and base-collector bias device bias. change depending on the pressure combination.

It should be noted that the position of the collector electrode 13 can also be grown under the substrate 7, and the working role is consistent with the growth of the collector electrode 13 on the top of the collector electrode 8 layer. In addition, on the same segment of the device structure, there may be multiple electrodes of the same type. For example, in FIG. 5 , a second collector electrode 13 can also be grown on the top of the collector electrode 8 layer on the left side of the quantum cascade structure layer 9 . Although the spatial positions of the two collector electrodes 13 are different, their roles in the device are the same, and they can all be classified as electrodes of the "collector electrode 13". Likewise, a second base electrode 14 can also be grown on top of the base 11 layer to the left of the emitter 12 layer, if the space allows, both of which are classified under the category "base electrode 14" electrode.

At the same time, the voltage of the emitter electrode of the strip-shaped straight waveguide 18 and the voltage of the emitter electrode of the S-shaped ring waveguide 19 may be the same or different, which mainly depends on the relevant application scenarios. In the embodiments of the present application, for convenience, it is assumed that the voltages of the emitter electrodes of the strip waveguide 18 and the emitter electrodes of the S-shaped ring waveguide 19 are the same unless otherwise specified. Similarly, the voltage of the base electrode in the center of the S-shaped ring waveguide 19 and the voltage of the base electrode outside the S-shaped ring waveguide 19 can also be controlled separately depending on the application scenario. In particular, it is assumed that the voltage of the base electrode in the center of the S-shaped ring waveguide 19 is the same as the voltage of the base electrode outside the S-shaped ring waveguide 19 .

Further, the quantum cascade structure layer 9 may be the quantum cascade structure layer 9 shown in FIG. 1( a ) or FIG. 1( b ). In this embodiment, the QCL stack unit of the quantum cascade structure layer 9 is corresponding to The ABB/…/ABB/…/ABB stack structure in Fig. 1(b). The layer plane of the quantum cascade structure layer 9 is parallel to the x-y plane, and the growth direction is along the z direction. The three-terminal S-type ring quantum cascade laser device is etched into a ridge-type waveguide structure along the y direction. The reflection end face of the structure is parallel to the x-z plane, the rear face is an enhanced reflection end face, and the front face is an anti-reflection end face. output end face.

As shown in FIG. 5 , the three electrodes of collector 8 , emitter 12 and base 11 are respectively applied with voltages V _c , V _e and V _b , then the base-emitter voltage is V _be =V _b −V _e , the collector-base voltage is V _cb =V _c -V _b . Then, in order to make the three-terminal S-type ring quantum cascade laser work normally, as shown in Figure 7, V _be > 0, V _cb > 0, that is, the base-emitter is in a forward biased state, and the collector is in a forward biased state. - The base is in a reverse biased state, then the energy level difference between the quasi-Fermi levels of the emitter 12 and the base 11 is eV _be , and the energy level difference between the quasi-Fermi levels of the base 11 and the collector 8 is eV _cb , where e is the primary charge. At this time, electrons are injected into the base electrode 11 region from the conduction band of the emitter electrode 12 region, enter the quantum level matching layer 10 , and then are injected into the quantum cascade structure layer 9 . It can be known from the knowledge of common triodes that the current of the collector 8 is controlled by the base 11-emitter 12 voltage V _be , that is, V _be controls the current density of the quantum cascade structure layer 9, and then controls the work or excitation of the entire quantum cascade structure layer 9. output intensity. At the same time, V _cb controls the device bias of the quantum cascade structure layer 9 , thereby controlling the electric field strength of the magnitude cascade structure, determining the energy level interval of the upper and lower subbands of the QCL subunit, and then controlling the entire quantum cascade structure layer 9 . working or lasing wavelength. With the three-terminal S-type ring quantum cascade laser shown in Fig. 5, we can decouple the working or lasing output intensity and wavelength of the quantum cascade structure layer 9 and control by _Vbe and _Vcb respectively.

In addition, it should be noted that, in general, when the current density injected into the quantum cascade structure layer 9 is controlled by V _be such that the total equivalent net charge of each QCL stack unit is zero, due to the periodicity of the stack structure, the quantum level The electric field of the cascading structure layer 9 will show a periodic change, similar to the electric field intensity change in FIG. 4 , at this time, the working or lasing output wavelength of the quantum cascade structure layer 9 is mainly controlled by V _cb .

In particular, when the current density of the injected quantum cascade structure layer 9 controlled by V _be such that the total equivalent net charge of each QCL stack unit is not zero, but as long as the total equivalent net charge of each QCL stack unit is less than With a certain critical value, the current density injected into the quantum cascade structure layer 9 can also be changed by fine-tuning the size of _Vbe , so that the Poisson potential of linear periodic variation when the total equivalent net charge of each QCL stack unit is zero Appropriate nonlinear changes occur, thereby enabling tuning control of the working or lasing output wavelength of the quantum cascade structure layer 9 .

As shown in FIG. 8 and FIG. 9 , it is a schematic structural diagram of a three-terminal S-type annular quantum cascade laser according to another embodiment of the present invention. In this embodiment, the strip-shaped straight waveguide 18 and the S-shaped annular waveguide 19 are deeply etched, That is, both the strip-shaped straight waveguide 18 and the S-shaped annular waveguide 19 include an emitter electrode, a base electrode, a quantum energy level matching layer, and a quantum cascade structure layer. Wherein, the material of the outer region of the S-shaped annular waveguide 19 is etched away, and the inner region of the S-shaped annular waveguide 19 is kept etched only to the top of the base region. Of course, the material in the circular region of the S-shaped annular waveguide 19 can also be etched away, while the outer region of the S-shaped annular waveguide 19 is kept etched only to the top of the base region.

The waveguide structure only includes the emitter type, and the cavity structure of the quantum cascade structure layer of the device is mainly of the F-P type. The S-type ring waveguide 19 structure will fine-tune the mode distribution and traveling wave mode in the F-P cavity of the device. When the S-shaped ring waveguide 19 structure includes an emitter, a base, a quantum energy level matching layer, and a quantum cascade structure layer, the resonant cavity structure of the quantum cascade structure layer of the whole device completely becomes a ring resonator, and the mode distribution and The traveling wave mode is completely distributed according to the device characteristics of the ring resonator. That is to say, the depth of etching determines the cavity resonance characteristics of the device. With the increase of the etching depth, the cavity resonance gradually changes from the F-P type resonance characteristics to the ring resonance cavity resonance characteristics.

As shown in FIG. 10 , a schematic diagram of the wide gain spectrum of the three-terminal S-type ring quantum cascade laser in this embodiment, when the base-emitter voltage V of the single-segment control three-terminal S-type ring quantum cascade laser When _be = V ₁ and the collector-base voltage is V _cb =V ₂ , the gain spectra of the three QCL subunits are given by dashed lines, and the superimposed broad gain spectrum is given by solid lines. Since the electric fields in the active regions of the three QCL subunits B2, B1 and A are shown in Fig. 4 and decrease in turn, the center energy of the gain spectrum of the three QCL subunits B2, B1 and A accordingly changes from high energy to low energy Decrease. By designing the corresponding QCL subunit parameters, the gain spectra of the three subunits can be superimposed into a flat broad spectrum.

As shown in FIG. 11 , schematic diagrams of two tunable wide-gain spectrums of the three-terminal S-type ring quantum cascade laser in this embodiment, under the specific device bias combination V _be = V ₁ , V _cb = V ₂ , the three The gain spectrum of each QCL subunit is the distribution curve shown by the dotted line. In Fig. 11(a), keeping V _be = V ₁ unchanged, when the collector-base voltage is changed from V ₂ to V _2' , the gain spectrum of the three QCL subunits moves to the high-energy direction, becoming The distribution curve is shown by the solid line. Optionally, in Fig. 11(b), keeping V _cb = V ₂ unchanged, when the base-emitter voltage V _be is changed from V ₁ to V _1' , the gain spectrum of the three QCL subunits goes up The energy direction moves and becomes the distribution curve shown by the solid line. For the clarity of the curve changes, the superposition results of the gain spectra of the three QCL subunits are not shown in Fig. 11 . However, similar to Fig. 10, it is easy to know that when the device bias combination is changed in Fig. 11(a) or Fig. 11(b), the overall gain spectrum of the device is also shifted to the high-energy direction, which is provided by the present invention. Broad-spectrum tunable gain characteristics of the quantum cascade structure layer 9.

As shown in FIG. 12 , schematic diagrams of two tunable gain spectra of the three-terminal S-type ring quantum cascade laser of this embodiment. In Fig. 12(a), keeping _{Vbe =} V1 unchanged, the three QCL subunits B2, B1 and _A work when the collector-base voltage _Vcb is V2 _" , V2 _' and V2, respectively .Under a specific device bias combination of V _be =V ₁ and V _cb =V ₂ , only A type of QCL sub-units can work normally among the three QCL sub-units of each QCL stack unit of the quantum cascade structure layer 9. In Under a specific device bias combination of V _be =V ₁ and V _cb =V _2' , only B1 type of QCL sub-units can work normally among the three QCL sub-units of each QCL stack unit in the quantum cascade structure layer 9. Under the device bias voltage combination V _be = V ₁ and V _cb = V _{2 ″} , only B2 kinds of QCL sub-units in the three QCL sub-units of each QCL stack unit of the quantum cascade structure layer 9 can work normally. shoot. It should be noted that both B1 and B2 are B-type QCL subunits. For the convenience of description, B1 and B2 are respectively referred to as B1-type QCL subunits and B2-type QCL subunits. Then keep V _be = V ₁ unchanged, when the collector-base voltage V _cb of the device changes from V ₂ to V _2' or V _2" , the gain spectrum of the quantum cascade structure layer 9 can be determined by A kind of QCL The gain spectrum of the subunit is tuned to the gain spectrum of the B1 or B2 QCL subunit, thereby realizing the tunable output of the quantum cascade structure layer 9 of the device.

In addition, as mentioned above, the current injected into the quantum cascade structure layer 9 can also be changed by fine-tuning the base-emitter bias voltage _Vbe while keeping the collector-base bias voltage V _cb unchanged. density, and then change the working or lasing output wavelength of the quantum cascade structure layer 9, as shown in Figure 12(b), when keeping V _cb =V ₂ unchanged, the three QCL subunits B2, B1 and A are respectively in the base The electrode-emitter bias _Vbe works when V _{1 ″} , V _1′ and V ₁ . Under a specific device bias combination of V _cb =V ₂ and V _be =V ₁ , the designed quantum cascade structure layer 9 has Among the three QCL subunits of each QCL stack unit, only A kind of QCL subunit can work normally. Under the specific device bias combination V _cb =V ₂ and V _be =V _{1 ′} , the designed quantum cascade structure layer 9 Among the three QCL subunits of each QCL stack unit, only B1 QCL subunits can work normally. Under the specific device bias combination V _cb =V ₂ and V _be =V _{1 "} , the designed quantum cascade structure layer Among the three QCL subunits of each QCL stack unit of 9, only B2 kinds of QCL subunits can work normally with gain spectrum lasing. Then keep V _cb = V ₂ unchanged, when the base-emitter bias voltage V _cb of the device is changed from V ₁ to V _1' or V _1" , the gain spectrum of the quantum cascade structure layer 9 can be determined by A The gain spectrum of the QCL subunit is tuned to the gain spectrum of the B1 type or B2 type QCL subunit, thereby realizing the tunable output of the quantum cascade structure layer 9 of the device.

Example 4

As shown in FIG. 13 and FIG. 14 , it is a schematic structural diagram of a three-terminal S-type ring quantum cascade laser with multi-segment control subunits (three-segment in this embodiment) that can be controlled by segments according to the present invention. In this embodiment, similar to FIG. 5 , the three-terminal S-type ring quantum cascade laser device is sequentially arranged from bottom to top along the z direction, the substrate 7 , the collector 8 , the quantum cascade structure layer 9 , the quantum energy level Matching layer 10 , base 11 and emitter 12 . Further, the collector electrode 8 includes a heavy n-doped lower cladding layer, and the emitter electrode 12 includes a top heavy n-doped upper cladding layer. Specifically, the layers of the device along the z direction from bottom to top are sequentially distributed as heavy n-doped substrate 7 layers, n-doped collector electrode 8, quantum cascade structure layer 9, quantum energy level matching layer 10, p-doped base electrode 11 and a heavy n-doped emitter 12. A collector electrode 13 (electrode c), an emitter electrode 15 (electrode e) and a base electrode 14 (electrode b) are grown on top of the collector electrode 8, the emitter electrode 12 and the base electrode 11.

Similarly, the position of the collector electrode 13 can also be grown under the substrate 7, and the working role is consistent with that of the collector electrode 13 grown on top of the collector electrode 8 layer. In addition, on the same device structure, like the three-terminal S-type ring quantum cascade laser shown in FIG. 5 , there can be multiple electrodes of the same type. For example, in FIG. 13 and FIG. 14 , in the quantum cascade structure layer 9 A second collector electrode 13 can also be grown on top of the collector 8 layer on the left. Although the spatial positions of the two collector electrodes 13 are different, their roles in the device are the same, and they can be assigned to the type of "collector electrode 13". Similarly, a second base electrode 14 can also be grown on top of the base 11 layer on the left side of the emitter 12 layer, if the space location permits, both of which are classified under the category "base electrode 14" electrode.

Further, the quantum cascade structure layer 9 may be the quantum cascade structure layer 9 as shown in FIG. 1( a ) or FIG. 1( b ). In this embodiment, the QCL stack unit of the quantum cascade structure layer 9 corresponds to The ABB/…/ABB/…/ABB stack structure in Figure 1(b). The layer plane of the quantum cascade structure layer 9 is parallel to the x-y plane, and the growth direction is along the z direction. The three-terminal S-type ring quantum cascade laser is etched into a ridge waveguide structure along the y direction. The reflection end face of the structure is parallel to the x-z plane, the rear face is an enhanced reflection face, and the front face is an anti-reflection face, that is, the light output of the device. end face.

Different from FIG. 5 , in this embodiment, the S-type ring waveguide 19 of the three-terminal S-type ring quantum cascade laser that can be controlled by segments and the top of the base layer outside the S-type ring waveguide 19 are etched with eight A strip-shaped window with a certain depth, as shown in FIG. 14, the strip-shaped window is filled with an insulating material to form an insulating layer 20, thereby forming a three-terminal S-shaped annular quantum stage with three-segment control subunits that can be controlled by segments. linked laser. The top electrodes of the three-terminal S-type ring quantum cascade laser are insulated from each other, so that the strip-shaped straight waveguide 18 emitter electrodes of the three-terminal S-type ring quantum cascade laser are independently controlled by V _ew . The emitter electrodes 15 corresponding to the annular waveguide 19 are independently controlled by V _e1 , V _e2 , and V _e3 respectively. The base electrode in the circular area of the S-shaped annular waveguide 19 is independently controlled by V _bi , while the circular The three base electrodes outside the area are independently controlled by V _b1 , V _b2 , and V _b3 . It should be pointed out that each control subunit can also correspond to a different collector control terminal. For simplicity, in this embodiment, the collectors of the three control subunits are shared, that is, the circuit bias model of the common collector is adopted. , the collector electrode 13 is independently controlled by _Vc . Then each control subunit is controlled by a set of bias voltage combinations, respectively, and the first, second and third control subunits are respectively controlled by (V _e1 , V _b1 , V _c ), (V _e2 , V _b2 , V _c ) and (V _e3 , V _b3 , V _c ) are independently controlled by three sets of bias voltages. Specifically, the length of each S-shaped annular waveguide 19 substructure in the three-stage control subunit along the axial direction of the S-shaped annular waveguide 19 is not specifically limited, and the width of the insulating layer 20 along the axial direction of the S-shaped annular waveguide 19 is also limited. There is no specific limitation, and corresponding changes and optimizations can be made according to the actual device design and application fields.

As shown in FIG. 15 and FIG. 16 , it is a schematic structural diagram of a three-terminal S-type ring quantum cascade laser that can be controlled in sections according to another embodiment of the present invention. The structure of the three-terminal S-type ring quantum cascade laser is added, and the insulating layer 20 is added to form a three-terminal S-type ring quantum cascade laser that can be controlled by multiple sections.

As shown in FIG. 17 , schematic diagrams of two kinds of wide gain spectra corresponding to the three-terminal S-type ring quantum cascade laser that can be controlled in sections of the present embodiment. In Figure 17(a), the base-emitter bias voltages of the first, second and third stage control subunits are all V ₁ , that is, V _be1 =V _b1 -V _e1 =V ₁ , V _be2 = V _b2 -V _e2 =V ₁ , V _be3 =V _b3 -V _e3 =V ₁ . As shown in FIG. 8 , under a specific collector-base bias voltage V ₂ , that is, V _cb1 =V _c −V _b1 =V ₂ , each element of the quantum cascade structure layer 9 designed by the first-stage control subunit is Among the three subunit structures of each QCL stack unit, only A type of QCL subunit structure can work normally. Under a specific collector-base bias voltage V _2' , that is, V _cb2 =V _c -V _b2 =V _2' , the second stage controls three of the QCL stack units of the quantum cascade structure layer 9 designed by the subunits Among the subunit structures, only B1 QCL subunit structures can work normally. Under a specific collector-base bias voltage V ₂ ″, that is, V _cb3 =V _c −V _b3 =V ₂ ″, the third stage controls the three stages of each QCL stack unit of the quantum cascade structure layer 9 designed by the subunit. Among the subunit structures, only B2 kinds of QCL subunit structures can work normally with gain spectrum lasing. Therefore, the gain spectrum of the finally designed three-terminal S-type ring quantum cascade laser is equivalent to the superposition of the gain spectrum shown by the three dashed lines in Fig. 17(a), forming the solid line in Fig. 17(a). The broad gain spectrum shown.

Similarly, in Fig. 17(b), the collector-base bias voltages of the control subunits of the first, second and third stages are all V ₂ , that is, V _cb1 =V ₂ , V _cb2 =V ₂ , V _cb3 =V ₂ . As shown in Fig. 12(b), under a specific base-emitter bias, that is, V _be1 =V ₁ , the first stage controls the quantum cascade structure layer 9 of the designed quantum cascade structure layer 9 of each QCL stack unit. Among the three subunit structures, only A kind of QCL subunit structure can work normally. Under a specific base-emitter bias, that is, V _be2 =V _1' , there are only B1 kinds of QCL subunits in the three subunit structures of each QCL stack unit in the quantum cascade structure layer 9 designed by the second-stage control subunit. The cell structure works fine. Under a specific base-emitter bias, that is, V _be3 =V _1” , there are only B2 kinds of QCL subunits in the three subunit structures of each QCL stack unit in the quantum cascade structure layer 9 designed by the third stage control subunit. The gain spectrum of the unit structure can work normally. Therefore, the gain spectrum of the finally designed three-terminal S-type ring quantum cascade laser is equivalent to the superposition of the gain spectrum shown by the three dotted lines in Fig. 17(b), A broad gain spectrum is formed as shown by the solid line in Fig. 17(b).

As shown in FIG. 18 , two kinds of tunable wide-gain spectrums corresponding to the three-terminal S-type ring quantum cascade laser that can be controlled in sections of the present embodiment are schematic diagrams. In particular, when the independent segment voltage in the three-terminal S-type ring quantum cascade laser shown in Fig. 17(a) is changed so that the base-emitter bias voltage of each segment control subunit remains unchanged, the is V ₁ , that is, V _be1 =V ₁ , V _be2 =V ₁ , and V _be3 =V ₁ . At the same time, the collector-base bias voltages of the first, second and third stage control subunits are changed from V ₂ to V ₃ , V _2' to V _3' , and V _2" to V _3" respectively. , namely V _cb1 =V ₃ , V _cb2 =V _3′ , V _cb3 =V _3″ , the gain spectrum of each control subunit segment structure changes from the dotted line spectrum shown in FIG. 18( a ) to the solid line spectrum. For the clarity of the curve changes, the superposition results of the gain spectra of the three subunit structures are not shown in Fig. 18(a). However, similar to Fig. 11(a), it is easy to see that when the collectors of the three subunit segments are independently controlled - The superimposed broad gain spectrum shown in Fig. 17(a) also changes with the collector-base bias of the three independent segments when the base bias is changed.

Similarly, when the individual segment voltages in the segment-controllable three-terminal S-type ring quantum cascade laser shown in Fig. 17(b) are changed such that each segment controls the collector-base bias of the subunit Keeping the same, all are still V ₂ , that is, V _cb1 =V ₂ , V _cb2 =V ₂ , and V _cb3 =V ₂ . At the same time, the base-emitter bias voltages of the control subunits of the first, second and third stages are changed from V ₁ to V ₃ , V _1' to V _3' , and V _1" to V _3" respectively. , namely V _be1 =V ₃ , V _be2 =V _3′ , V _be3 =V _3″ , the gain spectrum of each control subunit structure changes from the dotted line spectrum as shown in Figure 18(b) to the solid line spectrum. In order to For the clarity of the curve changes, the superposition of the gain spectra of the three subunit structures is not shown in Fig. 18(b). However, similar to Fig. 11(b), it is easy to see that when the base-emitter of the three subunits is independently controlled The superimposed broad gain spectrum shown in Figure 17(b) also changes with the base-emitter bias of the three independent segments when the polar bias is changed.

As shown in FIG. 19 , schematic diagrams of two kinds of ultra-broad gain spectra corresponding to the three-terminal S-type ring quantum cascade laser that can be controlled in sections of the present embodiment. In Figure 19(a), the base-emitter bias voltages of the first, second and third stage control subunits are all V ₁ , that is, V _be1 =V ₁ , V _be2 =V ₁ , V _be3 = _V1 . At the same time, the corresponding three collector-base bias voltages are respectively V _cb1 =V ₂ , V _cb2 =V _2′ , V _cb3 =V _2″ . As shown in FIG. 10 , each section of the control sub-unit is in Under the combination of base-emitter bias and collector-base bias of a specific device, all three QCL subunits can work normally, and the gain spectrum of the corresponding QCL stack unit is a gain spectrum with flat and broad spectrum characteristics , given by the dashed line in Fig. 19(a). Similar to Fig. 11(a), when the base-emitter bias of the single-segment control subunit is kept constant, at different collector-base biases, the QCL The wide gain spectrum of the stack unit can be tuned, and each segment of the control subunit has a different wide gain spectrum under the control of different collector-base biases, as indicated by the three dashed lines shown in Figure 19(a). As shown by the solid line in Fig. 19(a), the gain spectrum corresponding to the designed three-terminal S-type ring quantum cascade laser is the superposition of three broad gain spectra, thus forming an ultra-wide gain spectrum.

Similarly, in Fig. 19(b), the collector-base bias voltages of the first, second and third stage control subunits are all V ₂ , that is, V _cb1 =V ₂ , V _cb2 =V ₂ , V _cb3 =V ₂ . At the same time, the corresponding three base-emitter bias voltages are respectively V _be1 =V ₁ , V _be2 =V _1' , V _be3 =V _1" . Same as shown in Fig. 10, each control sub-unit is in the Under the combination of base-emitter bias and collector-base bias of a specific device, all three QCL subunits can work normally, and the gain spectrum of the corresponding QCL stack unit is a gain spectrum with flat and broad spectrum characteristics , given by the dashed line in Fig. 19(b). Similar to Fig. 11(b), when the collector-base bias of a single segment of the control subunit remains constant, under different base-emitter biases, the QCL The wide gain spectrum of the stack unit can be tuned, and each segment of the control subunit has a different broad gain spectrum under the control of different base-emitter biases, as indicated by the three dashed lines shown in Figure 19(b). As shown by the solid line in Fig. 19(b), the gain spectrum corresponding to the designed three-terminal S-type ring quantum cascade laser is the superposition of three broad gain spectra, thus forming an ultra-wide gain spectrum.

It should be specially pointed out that the changes in the combination of the collector-base bias and the base-emitter bias of the same segment of the control subunit in the above-mentioned embodiment are to keep one of the biases unchanged, and only change the other. a bias. However, in the specific implementation process, the method of simultaneously changing the collector-base bias voltage and base-emitter bias voltage of the device for different application fields can also obtain similar beneficial effects.

As shown in Fig. 20, the frequency-domain output power distribution diagram of the frequency comb output corresponding to the three-terminal S-type ring quantum cascade laser that can be sub-controlled in this embodiment is shown. In Fig. 20, the dotted line represents the gain spectrum of the corresponding three-terminal S-type ring quantum cascade laser, and the solid line represents the frequency comb output of the device. When combined with the strong four-wave mixing effect caused by the strong third-order nonlinearity of the quantum cascade structure and the mode-screening effect of the F-P cavity, it has any one of the broad gain spectra of Fig. 10, Fig. 11, Fig. 17 or Fig. 18. The three-terminal S-type ring quantum cascade laser, or the three-terminal S-type ring quantum cascade laser with the ultra-broad gain spectrum shown in Figure 19, can generate high-performance frequency combs with good tooth-comb spacing and tooth-comb power uniformity. In particular, the designed three-terminal S-type ring quantum cascade laser can produce a tunable high-performance frequency comb in combination with the tunable properties of either of the broad gain spectra in Fig. 17 or Fig. 18.

It should be pointed out that what is given here is only the distribution of the output high-performance frequency comb on the photon energy spectrum, and the corresponding output change diagram of the frequency comb in time is not given, but based on the definition of the frequency comb, the high-performance frequency comb Each tooth comb has a fixed phase relationship, and the phase relationship can be enhanced and fixed by the strong cascade-enhanced four-wave mixing effect caused by the strong third-order nonlinearity of the quantum cascade structure and the S-shaped ring waveguide 19 structure.

The external optical signal can be injected into the input section 17 of the straight straight waveguide 18, and the externally injected signal can interact with the signal in the structure of the S-shaped ring waveguide 19 through the coupling section 16 of the straight straight waveguide 18, affecting the S-shaped ring waveguide 19. The phase or mode locking of the signals within the structure changes the output characteristics of the frequency comb. In particular, the injection of an external optical signal enables the three-terminal S-type ring quantum cascade laser to be formed in the wavelength range of the tunable multi-wavelength output or broad-spectrum output capable of generating limited intensity, frequency and phase A chaotic laser with a noise-like wide-spectrum random output in a rapidly changing interval. In particular, in the multi-segment three-terminal S-type ring quantum cascade laser structure, different collector-base bias and base-emitter bias combinations of different segments can be controlled, and even the bar-shaped straight waveguide 18 can be changed The emitter electrode bias voltage V _ew can enhance the phase locking effect between the tooth combs of the output frequency comb, and can compress and shape the time domain waveform of the tooth comb of the output frequency comb.

Those of ordinary skill in the art will appreciate that the embodiments herein are for helping readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific modifications and combinations without departing from the essence of the present invention according to these technical teachings disclosed in the present invention, and these modifications and combinations still fall within the protection scope of the present invention.

Claims (16)

1. A three-terminal S-shaped ring quantum cascade laser is characterized in that: the laser comprises a substrate (7), a collector (8), a quantum level connection structure layer (9), a quantum level matching layer (10), a base (11) and an emitter (12) which are sequentially arranged from bottom to top, wherein the collector (8) and the quantum cascade structure layer (9) and the base (11) and the emitter (12) are arranged in a step shape;

the three-terminal S-shaped annular quantum cascade laser further comprises a collector electrode (13) arranged at the top of the collector electrode (8) or below the substrate (7), a base electrode (14) arranged at the top of the base electrode (11), and an emitter electrode (15) arranged at the top of the emitter electrode (12);

the laser is further etched with an S-shaped ring waveguide (19) and a bar-shaped straight waveguide (18) coupled with the S-shaped ring waveguide (19), the etching depths of the S-shaped ring waveguide (19) and the bar-shaped straight waveguide (18) are any depths from the top of an emitter to the top of a base (11), the top of a quantum energy level matching layer (10), the top of a quantum cascade structure layer (9) or the top of a collector (8), wherein at least one side in the annular region or outside the annular region of the S-shaped ring waveguide (19) is etched to a depth from the top of the emitter to the top of the base only, and the bar-shaped straight waveguide (18) comprises an input section (17) and a coupling section (16);

the quantum cascade structure layer (9) is formed by serially stacking at least two QC L stack units with the same structure, each QC L stack unit comprises at least two QC L sub-units with the same structure, each QC L sub-unit comprises an active region and an injection region, each injection region comprises a plurality of sections of doping regions, and the doping concentration parameters of at least one section of doping region are different between different QC L sub-units.

2. The three-terminal S-ring QCascade laser as claimed in claim 1, wherein at least one of the QC L subunits comprises two or more doped regions, and at least one doped region of the QC L subunit has a doping concentration parameter different from the doping concentration parameters of the other doped regions.

3. The three-ended S-shaped ring quantum cascade laser according to claim 1, wherein the quantum cascade structure layer (9) comprises N QC L stack units, namely a first QC L stack unit AB (1), an ith QC L stack unit AB (2), an Nth QC L stack unit AB (3), or a first QC L stack unit ABB (4), an ith QC L stack unit ABB (5), an Nth QC L stack unit ABB (6), wherein i and N are integers greater than 1, and i is less than or equal to N.

4. The three-terminal S-ring quantum cascade laser as claimed in claim 1, wherein the QC L subunits use a U-L state transition design, and the U and L states are any one of a single energy state, a multi-energy state, or a continuum state, and the multi-energy state comprises at least two energy states.

5. The three-terminal S-shaped ring quantum cascade laser according to claim 1, wherein the working or lasing wavelength corresponding to the active region of the QC L subunit is in the mid-infrared or terahertz band.

6. The three-terminal S-ring qc laser of claim 1, wherein: the three-terminal S-shaped annular quantum cascade laser comprises at least one collector electrode (13), at least one base electrode (14) and at least one emitter electrode (15).

7. The three-terminal S-ring qc laser of claim 1, wherein: and a plurality of insulating layers (20) are arranged on the S-shaped annular waveguide (19) and the base electrode (11) so that the laser forms a multi-section structure and is provided with a plurality of sections of control subunits.

8. The three-terminal S-ring qc laser of claim 7, wherein: the control subunit of each section can be controlled by a group of independent section voltages, the group of independent section voltages at least comprises three electrode control voltages of a collector electrode (8), a base electrode (11) and an emitter electrode (12), and the value of each group of independent electrode control voltages is any one of positive voltage, zero voltage or negative voltage.

9. The three-terminal S-ring qc laser of claim 7, wherein: in each segment of the control subunit, the base-emitter bias controls the current density of the quantum cascade structure layer (9) injected into the segment, and the base-collector bias controls the device bias of the quantum cascade structure layer (9) in the segment.

10. The three-terminal S-type ring quantum cascade laser as claimed in claim 7, wherein at least two of the QC L stack units are capable of operating or lasing, and at least one of the QC L subunits in each of the operating or lasing QC L stack units is capable of operating or lasing, under the applied base-emitter bias and base-collector bias device bias combinations.

11. The three-terminal S-ring QCascade laser as claimed in claim 7, wherein at least two of said QC L stack units are capable of operating or lasing simultaneously, and at least one of said QC L subunits in each of said operating or lasing QC L stack units is capable of operating or lasing at a particular applied base-emitter bias and base-collector bias device bias combination.

12. The three-terminal S-ring QCascade laser as claimed in claim 7, wherein at least two of said QC L stack units are capable of operating or lasing simultaneously when the applied base-emitter bias and base-collector bias device bias combination are changed, and at least one of said QC L subunits in each of said operating or lasing QC L stack units is capable of operating or lasing.

13. The three-terminal S-ring type quantum cascade laser as claimed in claim 7, wherein at least two of said QC L stack units can operate or lase simultaneously when the applied base-emitter bias and base-collector bias device bias combinations are changed, at least one of said QC L subunits in each of said operating or lasing QC L stack units can operate or lase, and the operating or lasing output wavelength is changed by changing the applied base-emitter bias and base-collector bias device bias combinations.

14. The three-terminal S-ring qc laser of claim 13, wherein: the working or lasing outputs are superimposed into a multi-wavelength output or a broad spectrum output or a frequency comb output.

15. The three-terminal S-ring qc laser of claim 13, wherein: the working or lasing outputs are superimposed into a multi-wavelength output or a wide-spectrum output or a frequency comb output that changes as the applied base-emitter bias and base-collector bias device bias combination changes.

16. The three-terminal S-ring qc laser of claim 15, wherein: under specific external light injection, chaotic laser can be formed in the wavelength range of the tunable multi-wavelength output or wide-spectrum output, and the chaotic laser output changes along with the change of an injected external signal or along with the change of the applied base-emitter bias voltage and the bias voltage combination of the base-collector bias device.

Images