CN110299589A - Frequency division and frequency multiplication generation method and device - Google Patents

Abstract

The present application discloses a method and device for generating frequency division and multiplication, which solves the problems of complex structure, high cost, low precision and low integration of the frequency division and multiplication device. The front-end laser, the phase region, and the back-end laser are sequentially integrated on the same substrate; the front-end laser and the back-end laser are injected into each other; the working wavelengths of the two lasers are different; the phase region tunes the coupling strength and The coupling phase changes the light injection ratio of the two lasers; the driving signal of the two lasers is a modulation signal, and by adjusting the frequency of the modulation signal, the frequency division or frequency multiplication of the microwave is realized; the output light of the back-end laser passes through the single The mode fiber is led out, converted into a modulated signal by the photodetector, and output through the radio frequency cable. The invention is simple to implement, and the generated modulation signal has high purity, high precision, compact structure, stable performance and low cost.

Description

A method and device for generating frequency division and multiplication

technical field

The present application relates to the field of optoelectronics, in particular to a frequency division and frequency multiplication generation method and device.

Background technique

The optical microwave transceiver system is a crucial component in microwave communication, electronic countermeasures, radar, remote control, remote sensing and many measurement systems. As the core of the transceiver system, the frequency multiplication and frequency division generation method and device play a key role in system performance. Due to the limitation of "electronic bottleneck", the traditional electric domain method to achieve microwave frequency multiplication and frequency division usually has disadvantages such as complex system structure, high cost, and poor stability; in addition, the generated modulation signal frequency (below a few GHz) is low Poor, especially, the phase noise degradation is about 6dB every time the frequency is doubled; the use of optical methods to achieve frequency division and frequency multiplication of modulated signals is also a common method, especially the optical injection-locked semiconductor laser system based on discrete devices. However, the polarization control is complicated, the structure is complex, the volume is large, the power consumption is high, and the coupling loss is large. If it is implemented with a general monolithic integrated laser, the two lasers are integrated on the same chip, share the same waveguide, and the same temperature controller, and the wavelength detuning of the two lasers cannot be achieved through temperature control.

Contents of the invention

Embodiments of the present application provide a method and device for generating frequency division and multiplication, which solve the problems of complex structure, high cost, and low precision and integration of the frequency division and multiplication device.

On the one hand, an embodiment of the present application proposes a frequency division and frequency multiplication generating device, including a front-end laser, a phase zone, a back-end laser, a single-mode optical fiber, a photodetector, and a radio frequency cable.

The front-end laser, the phase region, and the back-end laser are sequentially integrated on the same substrate. The front-end laser and the back-end laser are connected through a phase zone to realize mutual injection; the working wavelengths of the front-end laser and the back-end laser are different; the phase zone is composed of an active waveguide, and the length of the phase zone is 200-300 μm. Adjust the coupling strength and coupling phase between the front-end laser and the back-end laser through the electrodes to change the light injection ratio between the front-end laser and the back-end laser; the driving signal of the front-end laser or the back-end laser is a modulation signal , by adjusting the frequency of the modulation signal, microwave frequency division or frequency multiplication is realized; the output light of the back-end laser is drawn through the single-mode optical fiber, converted into a microwave signal by the photodetector, and output through the radio frequency cable .

Preferably, the front-end laser and the back-end laser are DFB lasers made by reconstruction-equivalent chirp technology.

Preferably, the front-end laser, the phase region, and the back-end laser have the same epitaxial material and structure; the material epitaxial structure is obtained by the traditional second-order metal-organic compound chemical vapor deposition method for material epitaxial growth, and the material epitaxial structure includes n-type substrate, n-type buffer layer, n-type confinement layer, strained multi-quantum well layer, p-type confinement layer, grating material layer, p-type cladding layer, p-type ohmic contact layer, p-type waveguide layer, insulating layer and Positive and negative electrodes.

Preferably, there is a first electrical isolation area between the front-end laser and the phase area, and a second electrical isolation area between the phase area and the back-end laser.

Preferably, the first electrical isolation region, the second electrical isolation region, the front-end laser, the phase region, and the rear-end laser share the same ridge waveguide structure;

Preferably, the first electrical isolation region and the second electrical isolation region are formed by etching away the grating structure and the ohmic contact layer by electron beam etching technology.

Preferably, the lengths of the first electrical isolation region and the second electrical isolation region are both in the range of 30-80 μm.

Preferably, the epitaxial materials used in the front-end laser, the phase region, and the back-end laser are at least A sort of.

Preferably, the wavelength interval between the front-end laser and the back-end laser is <0.5nm.

On the other hand, the present application also proposes a frequency division and multiplication generation method, which is used in the device described in any embodiment of the present application, including the following steps:

Adjusting the DC bias current of the front-end laser and/or the back-end laser, changing the frequency interval and light injection ratio between the front-end laser and the back-end laser, so that the device works in a double-cycle oscillation state ;

In the double-period oscillation state, the oscillating optical signals generated by the joint action of the front-end laser and the back-end laser are locked to each other;

Changing the frequency of the modulation signal, the modulation signal directly modulates the front-end laser or the back-end laser, and when the frequency of the modulation signal injected by the frequency source gradually approaches the double-cycle oscillation frequency, microwave frequency doubling is realized; gradually approaching the detuning frequency , realize the frequency division of microwave.

The above at least one technical solution adopted in the embodiment of the present application can achieve the following beneficial effects: the implementation method of the frequency division and frequency multiplication generation device is simple, the generated microwave signal spectrum has high purity, high accuracy, compact structure, stable performance, and low cost, among which Monolithically integrated inter-injection lasers are realized at low cost. It overcomes the shortcomings of traditional discrete devices, large volume of injection system, complex structure, and poor stability; it improves the control accuracy of the detuning frequency of the two lasers, improves the manufacturability and yield of monolithic integrated lasers, and reduces the manufacturing difficulty and manufacturing cost. The front-end laser and the back-end laser are modulated with low-cost and low-quality injected radio frequency signals to realize high-quality frequency division and frequency multiplication signal generation.

Description of drawings

The drawings described here are used to provide a further understanding of the application and constitute a part of the application. The schematic embodiments and descriptions of the application are used to explain the application and do not constitute an improper limitation to the application. In the attached picture:

Figure 1 is a schematic structural diagram of a frequency division and frequency multiplication generation device based on a monolithic integrated inter-injection laser;

Fig. 2 is a schematic structural diagram of a monolithic integrated laser;

Fig. 3 is a schematic diagram of the output spectrum in the double-period oscillation state;

Fig. 4 is the actual effect diagram of frequency division and frequency multiplication generation method of the present invention;

FIG. 5 is a control flow chart of the frequency division and multiplication generation method of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present application clearer, the technical solution of the present application will be clearly and completely described below in conjunction with specific embodiments of the present application and corresponding drawings. Apparently, the described embodiments are only some of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the scope of protection of this application.

The technical solutions provided by various embodiments of the present application will be described in detail below in conjunction with the accompanying drawings.

Fig. 1 is a schematic structural diagram of a frequency division and frequency multiplication generating device based on a monolithic integrated inter-injection laser.

The embodiment of the present application proposes a frequency division and frequency multiplication generating device, including a front-end laser 1 , a phase zone 2 , a back-end laser 3 , a single-mode optical fiber 4 , a photodetector 5 , and a radio frequency cable 6 .

The front-end laser, the phase region, and the back-end laser are sequentially integrated on the same substrate. The front-end laser and the back-end laser are connected through a phase zone to realize mutual injection; the working wavelengths of the front-end laser and the back-end laser are different; the phase zone is composed of an active waveguide, and the length of the phase zone is 200-300 μm. The coupling strength and coupling phase between the front-end laser and the back-end laser are tuned by the electrodes to change the light injection ratio of the front-end laser and the back-end laser. The driving signal of the front-end laser or the back-end laser is a modulation signal, and by adjusting the frequency of the modulation signal, frequency division or multiplication of the microwave is realized. The output light of the back-end laser is led out through the single-mode optical fiber, converted into a microwave signal by the photodetector, and output through the radio frequency cable.

In the prior art, the fabrication of integrated lasers is a combination of active waveguides and passive waveguides, and the fabrication process is complicated. The phase region of the embodiment of the present application only uses active waveguides, which avoids the complicated combination of active and passive waveguides in the manufacturing process of integrated lasers.

The light of the front-end laser is injected into the back-end laser through the phase region, and the light of the back-end laser is injected into the front-end laser through the phase region, and the two lasers realize mutual injection, thereby changing the physical characteristics of the two lasers (the modulation bandwidth increases , threshold current reduction, electro-optical conversion efficiency enhancement). By tuning the current in the phase region, the concentration of carriers in the phase region can be changed, thereby changing the refractive index and promoting the change of the optical path of light propagating in the phase region, thereby realizing the laser excitation of the front-end laser and the back-end laser. phase and intensity controls.

In addition, a section of pi phase shift is added in the center of the grating structure of the front-end laser and the back-end laser, which can effectively improve the single-mode performance of the front-end laser and the back-end laser. During the manufacturing process, the wavelength of light emitted by the front-end laser in the free-oscillation state is smaller than that of the back-end laser in the free-oscillation state, which is more conducive to the injection locking of the monolithic integrated laser.

In one embodiment of the present application, the monolithic integrated laser is packaged in a standard butterfly shape, with a total of 7 pins, which respectively control the temperature of the integrated laser and the currents of the two laser regions and the phase region. During the packaging process, the monolithic The chip of the integrated laser is dissociated, and the two sides of the integrated laser are coated with high-reflection film and anti-reflection film, so that more light can be fed back to the side of the back-end laser, and the power of the output light of the single-chip integrated laser can be increased. In this integrated laser, the output light will finally be output from the back-end laser port.

As shown in Fig. 1, externally injected modulation signal 71, monolithically integrated front-end laser 1, phase zone 2, monolithically integrated back-end laser 3, externally injected modulated signal 72, single-mode fiber 4, photodetector 5 , RF cable 6. In the above configuration, the monolithically integrated front-end laser, the back-end laser and the phase region between the two lasers constitute the main structure of the monolithically integrated laser.

It should be noted that, in order to enable the device of the present invention to work in a double-period oscillation state, the wavelength interval between the front-end laser and the back-end laser is <0.5 nm. The "double-period oscillation state" mentioned in this application document refers to an oscillation state in which the front-end laser and the back-end laser jointly enter under the condition of mutual optical injection, and the double-period oscillation optical signal generated is similar in spectrum to The frequency modulation is carried out on the main oscillation light wavelengths of the two lasers, and the modulation frequency is a double-period oscillation frequency. Generally, the modulation signal generated by the beat frequency of the photodetector contains the detuning frequency component of the front-end laser and the back-end laser and its corresponding sub-harmonic component (or double-period oscillation frequency component), which has a large bandwidth Tuning range, but due to the nonlinear effect of the injection-locked laser, the quality of the modulation signal generated by the beat frequency is poor.

It should also be noted that the modulation signals 71 and 72 can be respectively injected into the front-end laser or the back-end laser through the radio frequency port, or only 71 can be injected into the front-end laser or 72 can be injected into the back-end laser. If the front-end laser and the back-end laser are injected at the same time, the frequency of the injected modulation signals 71 and 72 needs to be the same.

Figure 2 is a schematic diagram of the monolithic integrated laser structure.

The front-end laser, the phase region, and the back-end laser share the same ridge waveguide structure. The front-end laser 1 , phase region 2 and back-end laser 3 have the same epitaxial material and structure. The epitaxial structure of the material is obtained by the epitaxial growth of the material by the traditional second-order metal organic compound chemical vapor deposition method, and the epitaxial structure of the material includes an n-type substrate, an n-type buffer layer, an n-type confinement layer, a strained multiple quantum well layer, p Type confinement layer, grating material layer, p-type cladding layer, p-type ohmic contact layer, p-type waveguide layer, insulating layer and positive and negative electrodes.

For example, the front-end laser and the back-end laser are DFB lasers made by reconstruction-equivalent chirp technology. Between the front-end laser and the phase region is a first electrical isolation region 8 , and between the phase region and the back-end laser is a second electrical isolation region 9 . The first electrical isolation region, the second electrical isolation region, the front-end laser, the phase region, and the rear-end laser share the same ridge waveguide structure. The first electrical isolation region and the second electrical isolation region are formed by etching away the grating structure and the ohmic contact layer by electron beam etching technology.

It should be noted that the lengths of the first electrical isolation region and the second electrical isolation region are both in the range of 30-80 μm. If the length is less than 30 μm, the electrical isolation region will prevent the electrodes of the front-end laser from interfering with the phase region, and the phase region from interfering with the electrodes of the back-end laser.

The monolithic integrated three-segment laser includes: n-type substrate 10; n-type buffer layer 11; n-type confinement layer 12; strained multiple quantum well layer 13; p-type confinement layer 14; grating material layer 15; Type cladding layer 16; p-type highly doped ohmic contact layer 17; SiO ₂ insulating layer 18; front-end laser positive electrode 19; phase region positive electrode 20; back-end laser positive electrode 21; negative electrode 22.

It should be noted that, in the frequency division and frequency multiplication generation device described in any embodiment of the present application, the epitaxial materials used in the front-end laser, phase region, and back-end laser are III-V compound semiconductor materials, II - At least one of Group VI compound semiconductor materials, Group IV-VI compound semiconductor materials, and Al-doped semiconductor materials.

Fig. 3 is a schematic diagram of a typical spectrum of the dual-period oscillation state of the integrated laser.

f _m is the main oscillating light mode of the front-end laser, f _s is the main oscillating light mode of the back-end laser, and the frequency difference (or detuning frequency) between the front-end laser and the back-end laser is f _r ; The monolithic integrated inter-injection laser generates an oscillating optical signal similar to the multi-level optical sidebands generated by frequency modulation of the modulation signal at the main oscillation mode of the front-end laser and the back-end laser in the double-period oscillation state, And the modulation frequency is a double-period oscillation frequency f ₀ (f ₀ =0.5×f _r ). Preferably, in the frequency division and frequency multiplication generating device, the frequency of the modulation signal injected into the front-end laser or the back-end laser is a detuning frequency or a double-cycle oscillation frequency, so that each light wave in a double-cycle oscillation state Signal injection locking, high-quality frequency division and frequency multiplication signals are obtained through the beating frequency of the photodetector.

Fig. 4 is an actual effect diagram of the frequency division and frequency multiplication generation method of the present invention.

The driving signal of the front-end laser or the back-end laser is a modulation signal, and when the frequency of the modulation signal injected into the front-end laser or the back-end laser is the detuning frequency f _r by adjusting the frequency of the modulation signal, after the division The output frequency of the frequency and frequency multiplication device is a modulation signal with a double-period oscillation frequency f ₀ to realize microwave frequency division; when the frequency of the modulation signal injected into the front-end laser or the back-end laser is a double-cycle oscillation frequency f ₀ , The frequency division and frequency multiplication device outputs the modulated signal f _r at the detuned frequency to realize microwave frequency multiplication.

It should be noted that the modulation signal can be injected into the front-end laser and or the back-end laser through the radio frequency port. Only one of the front-end laser or the back-end laser needs to be injected at a time. If the front-end laser and the back-end laser are injected at the same time, the frequency of the injected modulation signal needs to be the same.

FIG. 5 is a control flow chart of the frequency division and multiplication generation method of the present invention. The device used in any one of the embodiments of the present application includes the following steps:

Step 101, adjusting the DC bias current of the front-end laser and/or the back-end laser, changing the frequency interval and light injection ratio between the front-end laser and the back-end laser, so that the device works at double Periodic oscillation state;

In step 101, the front-end laser and the back-end laser are designed and manufactured by using reconstruction-equivalent chirp technology, which facilitates the precise regulation of the operating wavelength of the monolithic integrated laser; in addition, careful tuning is required in the specific implementation The magnitude of the bias current in the phase region between the two laser regions has the effect of further fine-tuning the detuning frequency between the front-end laser and the back-end laser.

Step 102. In the double-period oscillation state, change the frequency of the modulation signal so that the oscillating optical signals generated by the joint action of the front-end laser and the back-end laser are locked to each other; use the modulation signal to directly modulate the front-end laser and or The back-end laser implements microwave frequency multiplication when the frequency of the modulation signal injected by the frequency source is gradually approaching the double-period oscillation frequency; and realizes microwave frequency division when gradually approaching the detuning frequency.

For example, the modulation signal can be loaded on the front-end laser or on the back-end laser.

It should be noted that, in this application: the modulation signal used for direct modulation to the monolithic integrated laser, its modulation frequency is the detuning frequency or double-cycle oscillation frequency of the front-end laser and the back-end laser, The double-period oscillation frequency is half of the detuning frequency of the front-end laser and the back-end laser.

The invention provides a frequency division and frequency multiplication generating device with compact structure and stable performance and its realization method, and the used monolithic integrated laser is realized at low cost. The invention realizes the double-period oscillation of the DFB laser by means of a monolithic integrated laser, and overcomes the traditional disadvantages of many discrete devices, large volume of injection system, complex structure, poor stability and the like.

In the embodiment of the present invention, the grating of the monolithic integrated DFB laser is manufactured by using the reconstruction-equivalent chirp technology, and the wavelength of the two lasers can be precisely controlled by controlling the sampling grating period of the μm order, and the detuning frequency is improved. The control precision of the monolithic integrated laser is improved, thereby improving the manufacturability and yield of the double-period oscillation state of the monolithic integrated laser, and reducing the manufacturing difficulty and manufacturing cost of the monolithic integrated laser.

It should also be noted that the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also includes Other elements not expressly listed, or elements inherent in the process, method, commodity, or apparatus are also included. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

The above descriptions are only examples of the present application, and are not intended to limit the present application. For those skilled in the art, various modifications and changes may occur in this application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims (10)

1. A frequency division and frequency multiplication generating device, comprising a front-end laser, a phase region, a back-end laser, a single-mode optical fiber, a photodetector, a radio frequency cable, is characterized in that, The front-end laser, the phase region, and the back-end laser are sequentially integrated on the same substrate; The front-end laser and the back-end laser are connected through a phase region to achieve mutual injection; the front-end laser and the back-end laser have different operating wavelengths; The phase region is composed of an active waveguide, and the length of the phase region is 200-300 μm. The coupling strength and coupling phase between the front-end laser and the back-end laser are adjusted by electrodes, and the distance between the front-end laser and the back-end laser is changed. light injection ratio; The driving signal of the front-end laser or the back-end laser is a modulation signal, and by adjusting the frequency of the modulation signal, microwave frequency division or frequency multiplication is realized; The output light of the back-end laser is led out through the single-mode optical fiber, converted into a microwave signal by the photodetector, and output through the radio frequency cable. 2. The frequency division and frequency multiplication generation device according to claim 1, characterized in that, the front-end laser and the back-end laser are DFB lasers made by reconstruction-equivalent chirp technology. 3. frequency division and frequency multiplication generation device according to claim 1, is characterized in that, The front-end laser, phase region, and back-end laser have the same epitaxial material and structure; The epitaxial structure of the material is obtained by the epitaxial growth of the material by the traditional second-order metal organic compound chemical vapor deposition method, and the epitaxial structure of the material includes an n-type substrate, an n-type buffer layer, an n-type confinement layer, a strained multiple quantum well layer, p Type confinement layer, grating material layer, p-type cladding layer, p-type ohmic contact layer, p-type waveguide layer, insulating layer and positive and negative electrodes. 4. The frequency division and frequency multiplication generating device according to claim 1, characterized in that, between the front-end laser and the phase region is a first electrical isolation region, and between the phase region and the back-end laser is the second electrical isolation region. 5 . The frequency division and frequency multiplication generating device according to claim 4 , wherein the front-end laser, the phase region, the back-end laser, the first electrical isolation area and the second electrical isolation area share the same ridge waveguide structure. 6. The frequency division and frequency multiplication generating device according to claim 4, characterized in that, the first electrical isolation area and the second electrical isolation area are etched away from the grating structure and ohmic contact by electron beam etching technology layer made. 7. The frequency division and frequency multiplication generating device according to any one of claims 1 to 6, characterized in that the lengths of the first electrical isolation region and the second electrical isolation region are both in the range of 30 to 80 μm . 8. The frequency division and frequency multiplication generating device according to any one of claims 1 to 6, characterized in that the epitaxial materials used in the front-end laser, phase region, and back-end laser are III-V compound semiconductor materials , at least one of II-VI compound semiconductor materials, IV-VI compound semiconductor materials, and aluminum-doped semiconductor materials. 9. The frequency division and frequency multiplication generating device according to any one of claims 1-6, characterized in that the wavelength interval between the front-end laser and the back-end laser is <0.5nm. 10. A frequency division and frequency multiplication generation method, used for the device described in any one of claims 1 to 9, characterized in that it comprises the following steps: Adjusting the DC bias current of the front-end laser and/or the back-end laser, changing the frequency interval and light injection ratio between the front-end laser and the back-end laser, so that the device works in a double-cycle oscillation state ; Changing the frequency of the modulation signal, the modulation signal directly modulates the front-end laser or the back-end laser, and when the frequency of the modulation signal injected by the frequency source gradually approaches the double-cycle oscillation frequency, microwave frequency doubling is realized; gradually approaching the detuning frequency , realize the frequency division of microwave.