KR101221873B1 - Multiple distributed feedback laser devices - Google Patents

Abstract

Provided is a multi-distribution feedback laser device. The laser device has an active layer disposed on a substrate of a first distributed feedback region, a modulation region and a second distributed feedback region, a first diffraction grating coupled with an active layer of a first distributed feedback region, and an active layer of a second distributed feedback region. And a second diffraction grating. The laser element also includes a first micro heater for supplying heat to the first diffraction grating, and a second micro heater for supplying heat to the second diffraction grating. The first micro heater and the second micro heater are controlled independently of each other.

Description

Multi-distribution feedback laser device {MULTIPLE DISTRIBUTED FEEDBACK LASER DEVICES}

The present invention relates to laser devices, and more particularly, to a multi-distribution feedback laser device.

Semiconductor-based optical devices may be manufactured using semiconductor processes such as a growth process, a photolithography process, an etching process, and / or a deposition process. By using semiconductor processes, semiconductor-based optical devices can have advantages such as miniaturization, low manufacturing cost, and / or mass production. Accordingly, many studies on semiconductor-based optical devices have been conducted.

Among semiconductor-based optical devices, functional laser devices for selecting a specific wavelength such as a distributed feedback laser diode and / or a distributed Bragg reflector laser diode have been developed. Such functional laser devices can perform wavelength filtering using a diffraction grating. For example, only light waves having a specific wavelength whose light waves correspond to Bragg wavelengths due to periodic refractive index changes may be reflected. In this way, wavelength filtering may be performed. Reflected light waves of a particular wavelength may be fed back to the gain region and oscillated. Such a functional laser device may be used as a light source for generating terahertz (THz) waves by photomixing as well as a light source for optical communication.

Terahertz wave generation methods include frequency doubling method, backward wave oscillator, photomixing method, carbon dioxide pumping gas laser, quantum cascade laser, and free electron laser. exist. In the photomixing method, a beating signal of two laser diodes having different wavelengths is incident on a photomixer to secure terahertz waves of frequencies corresponding to the beating period. For the photomixing method, at least one frequency of two laser beams must be stably and continuously tuned. In addition, it may be required to match the characteristics of the two laser beams. In order to secure these requirements, additional devices are required, so that the terahertz wave generating equipment by the photomixing method can be enlarged and the structure becomes complicated, and the manufacturing cost of the equipment can be increased.

One technical problem to be achieved by the present invention is to provide a multi-distribution feedback laser device with excellent reliability.

Another object of the present invention is to provide a highly integrated multi-distribution feedback laser device.

Another technical object of the present invention is to provide a multi-distribution feedback laser device capable of increasing the efficiency of terahertz wave generation.

To provide a multi-distribution feedback laser device for solving the above technical problems. The laser device comprises: a substrate comprising a first distributed feedback region, a modulation region, and a second distributed feedback region; An active layer on a substrate of said first distributed feedback, modulation and second distributed feedback regions; A first diffraction grating disposed in the first distributed feedback region and coupled to an active layer of the first distributed feedback region; A second diffraction grating disposed in the second distributed feedback region and coupled to an active layer of the second distributed feedback region; A first micro heater for supplying heat to the first diffraction grating; And a second micro heater supplying heat to the second diffraction grating. The first micro heater and the second micro heater are controlled independently of each other.

According to an embodiment, the refractive index of the first diffraction grating may be changed by heat supplied from the first micro heater, and the refractive index of the second diffraction grating may be changed by heat supplied from the second micro heater. have.

According to an embodiment, the temperature of the heat supplied by the first micro heater to the first diffraction grating may be different from the temperature of the heat supplied by the second micro heater to the second diffraction grating.

According to one embodiment, the laser device comprises a lower cladding layer interposed between the active layer and the substrate; And an upper cladding layer disposed on the active layer. The lower cladding layer may include a compound semiconductor doped with a dopant of a first type, and at least an upper portion of the upper cladding layer may include a compound semiconductor doped with a dopant of a second type.

According to an embodiment, the first laser current may be supplied to the active layer of the first distributed feedback region to oscillate a first light source having a first wavelength, and the second laser current may be applied to the active layer of the second distributed feedback region. The second light source of the second wavelength may be oscillated by supply. Reverse bias may be applied to the upper cladding layer, the active layer, and the lower cladding layer of the modulation region to generate an electric field absorption phenomenon in the modulation region.

According to one embodiment, the first diffraction grating and the second diffraction grating may be disposed in the upper cladding layer.

According to one embodiment, the laser device comprises a first separate confinement hetero layer interposed between the lower cladding layer and the active layer, and having a bandgap wavelength smaller than the active layer; And a second separation-limited heterolayer interposed between the upper cladding layer and the active and having a bandgap wavelength smaller than that of the active layer.

According to an embodiment, the first micro heater may be disposed above the upper cladding layer of the first distributed feedback region, and the second micro heater may be disposed above the upper cladding layer of the second distributed feedback region. have. The first and second micro heaters are electrically insulated from the upper cladding layer.

According to one embodiment, the laser device comprises: a first electrode electrically connected to an upper cladding layer in the first distributed feedback region; A second electrode electrically connected to an upper cladding layer in the second distributed feedback region; A third electrode electrically connected to an upper cladding layer in the modulation region; A first interlayer insulating pattern interposed between the first electrode and the first micro heater; And a second interlayer insulating pattern interposed between the second electrode and the second micro heater.

According to one embodiment, at least one of the first diffraction grating and the second diffraction grating may be a complex coupling diffraction grating.

According to one embodiment, the active layer may be formed of a multi-quantum well structure.

According to an embodiment, the period of the first diffraction grating and the period of the second diffraction grating may be the same.

According to an embodiment, the period of the first diffraction grating and the period of the second diffraction grating may be different from each other.

According to one embodiment, the first and second diffraction gratings may be doped with n-type or p-type dopants.

According to the multi-distribution feedback laser device described above, it is possible to adjust the wavelength difference between the first light source and the second light source oscillated by the first and second micro heaters controlled independently of each other. Thus, the first and second light sources, which are very stable, can be oscillated. As a result, it is possible to implement a multi-distribution feedback laser device with excellent reliability.

In the multi-distribution feedback laser device, the first distribution feedback region, the modulation region, and the second distribution feedback region are integrated on the substrate, and the active layer is disposed within the modulation region as well as the distribution feedback regions. That is, the active layer may be continuously disposed on a substrate of the first distribution feedback, modulation and second distribution feedback regions. Accordingly, the first light source and the second light source having coherent characteristics can be stably continuously oscillated. For example, by integrating a plurality of distributed feedback laser elements each oscillating in one resonator, the phases of the oscillating waves respectively oscillated can be coupled to each other and correlated with each other. As a result, a phenomenon in which the phase difference of the oscillation waves is locked may be induced. As a result, it is possible to continuously generate highly stable multi-mode oscillations that are key to terahertz wave generation. In addition, it is possible to implement a highly integrated multi-distribution laser device.

Furthermore, at least one of the diffraction gratings may be a complex coupled diffraction grating. Accordingly, an output having a very large modulation index can be obtained. As a result, the generation efficiency of terahertz waves generated by using the first and second light sources may be very high.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and to fully convey the spirit of the invention to those skilled in the art. In the drawings, the thicknesses of layers (or films) and regions are exaggerated for clarity. In addition, where it is said that a layer (or film) is "on" another layer (or film) or substrate, it may be formed directly on another layer (or film) or substrate or a third layer between them. (Or membrane) may be interposed. The expression 'and / or' is used herein to include at least one of the components listed before and after. Portions denoted by like reference numerals denote like elements throughout the specification.

1 is a cross-sectional view showing a multi-distribution feedback laser device according to an embodiment of the present invention.

Referring to FIG. 1, an active layer 106 is disposed on a substrate 100 including a first distributed feedback region (DFB1), a modulation region (P), and a second distributed feedback region (DFB2). . The active layer 106 is disposed on the substrate 100 of the first distribution feedback, modulation and second distribution feedback regions DFB1, P and DFB2. The modulation area P may be disposed between the first distribution feedback area DFB1 and the second distribution feedback area DFB2. The substrate 100 may be formed of a compound semiconductor. For example, the substrate 100 may be an indium phosphorus (InP) substrate.

The active layer 106 may be continuously disposed along the substrate 100 of the first distribution feedback, modulation, and second distribution feedback regions DFB1, P, and DFB2. The active layer 106 may be formed of a compound semiconductor. The active layer 106 may be formed in a multi-quantum well structure. For example, the active layer 106 may be formed by alternately stacking a first InGaAsP layer and a second InGaAsP layer having different band gaps. According to an embodiment of the present invention, the active layer 106 may be in a bulk form formed of InGaAsP having a bandgap wavelength of about 1.55 μm. The active layer 106 is preferably in an intrinsic state.

A lower cladding layer 102 may be interposed between the active layer 106 and the substrate 100. The lower cladding layer 102 may be formed of a compound semiconductor doped with a first type dopant. An upper cladding layer 125 may be disposed on the active layer 106. At least an upper portion of the upper cladding layer 125 may be formed of a compound semiconductor doped with a second type dopant. One of the first type dopant and the second type dopant is an n-type dopant, and the other is a p-type dopant. For example, the lower cladding layer 102 may be formed of n-type indium phosphorus (InP), and at least an upper portion of the upper cladding layer 125 may be formed of p-type indium phosphorus (InP). Alternatively, the lower cladding layer 102 may be formed of p-type indium phosphorus (InP), and at least an upper portion of the upper cladding layer 125 may be formed of n-type indium phosphorus (InP). In the present embodiment, for convenience of description, the lower cladding layer 102 is formed of n-type indium phosphorus (InP), and at least an upper portion of the upper cladding layer 125 is formed of p-type indium phosphorus (InP). The case will be described.

A first separate hetero layer 104 may be interposed between the active layer 106 and the lower cladding layer 102. The first limited hetero layer 104 may be formed of a compound semiconductor having a band gap wavelength smaller than the band gap wavelength of the active layer 106. For example, the first isolation-limited heterolayer 104 may be formed of InGaAsP having a bandgap wavelength of about 1.3 μm. A second separation-limited heterolayer 108 may be interposed between the active layer 106 and the upper cladding layer 125. The second limited hetero layer 108 may be formed of a compound semiconductor having a band gap wavelength smaller than the band gap wavelength of the active layer 106. For example, the second limited hetero layer 108 may be formed of InGaAsP having a bandgap wavelength of about 1.3 μm. Each of the first and second isolation-limited heterolayers 104 and 108 may be formed to a thickness of about 0.1 μm. However, the present invention is not limited thereto. Each of the first and second isolation-limited heterolayers 104 and 108 may be formed in a different thickness. The first and second discrete hetero layers 104 and 108 may be in an intrinsic state.

A first diffraction grating 112a is disposed in the first distributed feedback region DFB1, and a second diffraction grating 112b is disposed in the second distributed feedback region DFB2. The diffraction grating is not disposed in the modulation region P. The first diffraction grating 112a is coupled with an active layer 106 in the first distributed feedback region DFB1, and the second diffraction grating 112b is an active layer in the second distributed feedback region DFB2. Coupled with 106. Light generated in the active layer 106 in the first distribution feedback region DFB1 may be Bragg-reflected by the first diffraction grating 112a, so that a first light source having only a first wavelength may be oscillated. Light generated in the active layer 106 in the second distribution feedback region DFB2 may be Bragg-reflected by the second diffraction grating 112b, so that a second light source having only a second wavelength may be oscillated.

The first diffraction grating 112a may be disposed in the upper cladding layer 125 in the first distributed feedback region DFB1, and the second diffraction grating 112b is in the second distributed feedback region DFB2. It may be disposed in the upper cladding layer 125. More specifically, the upper cladding layer 125 may include a first upper cladding layer 122 and a second upper cladding layer 124 sequentially stacked. In this case, the first diffraction grating 112a is disposed in the first upper cladding layer 122 in the first distribution feedback region DFB1, and the second diffraction grating 112b is the second distribution feedback region. And may be disposed in the first upper cladding layer 122 in the DFB2. The second upper cladding layer 124 may be formed of a compound semiconductor doped with a second type dopant. For example, when the lower cladding layer 102 is formed of n-type indium phosphorus (InP), the second upper cladding layer 124 may be formed of p-type indium phosphorus (InP). The first upper cladding layer 122 surrounding the diffraction gratings 112a and 112b may be formed of an undoped compound semiconductor (eg, undoped indium). Alternatively, the first upper cladding layer 122 may be formed of a compound semiconductor (eg, p-type indium, etc.) doped with the same type of dopant as the second upper cladding layer 124.

The period of the first diffraction grating 112a may be the same as the period of the second diffraction grating 112b. Alternatively, according to an embodiment of the present invention, the period of the first diffraction grating 112a may be different from the period of the second diffraction grating 112b. In addition, the shape of the first diffraction grating 112a may be the same as or different from that of the second diffraction grating 112b.

At least one of the first and second diffraction gratings 112a and 112b may be a complex coupled diffraction grating. The first and second diffraction gratings 112a and 112b may be formed of a compound semiconductor for complex coupling. For example, the first and second diffraction gratings 112a and 112b may be formed of InGaAs. The first and second diffraction gratings 112a and 112b may be doped with an n-type dopant or a p-type dopant. However, the present invention is not limited thereto. At least one of the first and second diffraction gratings 112a and 112b may be an index coupled diffraction grating.

The first electrode 128a is electrically connected to the upper cladding layer 125 in the first distributed feedback region DFB1, and the second electrode 128b is the upper cladding layer in the second distributed feedback region DFB2. And electrically connected to 125. The third electrode 128c is electrically connected to the upper cladding layer 125 in the modulation region P. The first, second, and third electrodes 128a, 128b, and 128c are upper cladding layers 125 of the first distributed feedback region DFB1, the second distributed feedback region DFB2, and the modulation region P, respectively. Are each disposed on The first, second and third electrodes 128a, 128b, 128c are spaced apart from each other by the isolation trench 130. The electrodes 128a, 128b, and 128c may be formed of metal. An isolation insulating pattern 132 may be disposed in the isolation trench 130. That is, the isolation insulating pattern 132 may be disposed between the first, second and third electrodes 128a, 128b, and 128c. The isolation insulating pattern 132 may include at least one selected from oxides, nitrides, and oxynitrides. The isolation trench 130 may extend downward to be formed on an upper portion of the upper cladding layer 125. That is, the bottom surface of the isolation trench 130 may be lower than the top surface of the upper cladding layer 125. Due to the isolation trench 130, the elements ex and the diodes in the regions DFB1, P and DFB2 may operate independently of each other. The isolation trench 130 is preferably at a depth capable of independent operations of the elements in the regions DFB1, P and DFB2. In addition, the isolation trench 130 may have a depth that minimizes coupling with the light waves of the oscillated specific wavelength. That is, the depth of the isolation trench 130 is preferably appropriate in consideration of independent operations of the elements in the regions DFB1, P, and DFB2 and minimizing coupling with the oscillated light waves.

A first ohmic pattern 126a may be disposed between the first electrode 128a and the upper cladding layer 120 of the first distribution feedback region DFB1. A second ohmic pattern 126b may be disposed between the second electrode 128b and the upper cladding layer 120 of the second distribution feedback region DFB2, and the third electrode 128c and the modulation region P The third ohmic pattern 126c may be disposed between the upper cladding layers 120 of the (). The first, second and third ohmic patterns 126a, 126b, and 126c may be separated from each other by the isolation insulating pattern 132. The ohmic patterns 126a, 126b, and 126c may be formed of the same material. For example, the ohmic patterns 126a, 126b, and 126c may be formed of InGaAs.

A first micro heater 136a for supplying heat to the first diffraction grating 112a is disposed in the first distribution feedback region DFB1, and the second diffraction grating (DFB2) is disposed in the second distribution feedback region DFB2. A second micro heater 136b is arranged to supply heat to 112b). The first micro heater 136a may be disposed above the upper cladding layer 125 in the first distribution feedback region DFB1. In this case, the first micro heater 136a is preferably electrically insulated from the upper cladding layer 125. The second micro heater 136b may be disposed above the upper cladding layer 125 in the second distributed feedback region DFB2. In this case, the second micro heater 136a is preferably electrically insulated from the upper cladding layer 125. The first micro heater 136a and the second micro heater 136b are controlled independently of each other. The refractive index of the first diffraction grating 112a is changed by the heat supplied by the first micro heater 136a. The refractive index of the second diffraction grating 112b is changed by the heat supplied by the second micro heater 136b. The temperature of the heat supplied by the first micro heater 136a may be different from the temperature of the heat supplied by the second micro heater 136b. In this case, one of the temperatures of the heat supplied by the first and second micro heaters 136a and 136b may be 0 ° C. That is, the fact that the temperatures of the heats supplied by the first and second micro heaters 136a and 136b are different is that either one of the first and second micro heaters 136a and 136b supplies heat of a predetermined temperature. And the other includes not supplying heat.

The first and second micro heaters 136a and 136b may supply heat to the first and second diffraction gratings 112a and 112b using Joule's heat. The first and second micro heaters 136a and 136b may be formed of a material having electrical resistance. For example, the first and second micro heaters 136a and 136b may be formed of a metal such as chromium (Cr) and gold (Au). According to an embodiment of the present invention, chromium (Cr) included in the micro heaters 136a and 136b may be used as a resistor. According to an embodiment of the present invention, gold included in the micro heaters 136a and 136b may be used for bonding with a connection ball and / or a resistor. However, the present invention is not limited thereto. The first and second micro heaters 136a and 136b may be formed of other materials having electrical resistance.

The first micro heater 136a may be disposed on the first electrode 128a. A first interlayer insulating pattern 134a may be interposed between the first electrode 128a and the first micro heater 136a. The second micro heater 136b may be disposed above the second electrode 128b. A second interlayer insulating pattern 134b may be interposed between the second electrode 128b and the second micro heater 136b. The first and second micro heaters 136a and 136b may be electrically insulated from the first and second electrodes 128a and 128b by the interlayer insulating patterns 134a and 134b. As a result, the first and second micro heaters 136a and 136b and the first and second electrodes 128a and 128b may be independently controlled. The first and second interlayer insulating patterns 134a and 134b may extend laterally and be connected to each other. The first and second interlayer insulating patterns 134a and 134b may include at least one selected from oxides, nitrides, and oxynitrides.

The lower cladding layer 102, the first limited hetero layer 104, the active layer 106, the second limited hetero layer 108, the first diffraction grating 112a in the first distributed feedback region DFB1, and The upper cladding layer 125 may be included in the first distributed feedback laser diode. The lower cladding layer 102, the first separated heterolayer 104, the active layer 106, the second separated heterolayer 108, the second diffraction grating 112b in the second distributed feedback region DFB2, and The upper cladding layer 125 may be included in the second distributed feedback laser diode. The lower cladding layer 102, the first separated heterolayer 104, the active layer 106, the second separated heterolayer 108 and the upper cladding layer 125 in the modulation region P are included in the modulation diode. Can be.

A first laser current may be supplied to the active layer 106 of the first distributed feedback laser diode through the first electrode 128a. The first laser current may be supplied to the first electrode 128a by applying a forward bias to the first distributed feedback laser diode. Light is generated in the active layer 106 of the first distribution feedback region DFB1 by the first laser current, and the generated light is Bragg-reflected by the first diffraction grating 112a so that only a first wavelength is generated. The first light source having can be oscillated. The first wavelength of the first light source may be changed by a change in the refractive index of the first diffraction grating 112a. For example, the first wavelength of the first light source may be proportional to the refractive index of the first diffraction grating 112a. The refractive index of the diffraction grating 112a is changed by supplying a first heater current to the first micro heater 136a and supplying heat of a first temperature to the first diffraction grating 112a. Accordingly, the first wavelength of the first light source may be changed. That is, the first wavelength of the first light source may be changed by the first heater current supplied to the first micro heater 136a.

A second laser current may be supplied to the active layer 106 of the second distributed feedback laser diode through the second electrode 128b. The second laser current may be supplied to the second electrode 128b by applying a forward bias to the second distributed feedback laser diode. Light is generated in the active layer 106 of the second distributed feedback region DFB2 by the second laser current, and the generated light is Bragg reflected by the second diffraction grating 112b so that only the second wavelength is emitted. The second light source having can be oscillated. The second wavelength of the second light source may be changed by the change of the refractive index of the second diffraction grating 112b. The refractive index of the second diffraction grating 112b is changed by supplying a second heater current to the second micro heater 136b and supplying heat of a second temperature to the second diffraction grating 112b. Accordingly, the second wavelength of the second light source may be changed. That is, the second wavelength of the second light source may be changed by the second heater current supplied to the second micro heater 136b.

A reverse bias may be applied to the modulation diode through the third electrode 128c. Accordingly, an electro absorption phenomenon may occur in the modulation diode. By the electric field absorption of the modulation diode, the side modes except the main oscillation mode of the first and second light sources may be absorbed. Accordingly, the loss of the first and second light sources can be minimized. The modulation region P in which the modulation diode is formed may have a limited width (eg, a distance between the first and second distributed feedback regions DFB1 and DFB2) in order to minimize light loss. For example, the modulation area P may have a width of 50 μm or less.

An operation method of the multi-distribution feedback laser device described above will be described. The first and second laser currents are supplied to the first and second distributed feedback laser diodes through the first and second electrodes 128a and 128b, respectively. Accordingly, the first light source of the first wavelength and the second light source of the second wavelength are respectively oscillated from the first and second distributed feedback laser diodes. At least one of the first and second micro heaters 136a and 136b may be operated to change at least one wavelength of the first and second light sources. As a result, the first and second light sources having different wavelengths can be oscillated.

According to one embodiment of the present invention, the second heater current may be supplied to the second micro heater 136b without operating the first micro heater 136a. In this case, the second heater current can be continuously changed. According to the change of the second heater current, the temperature of the heat supplied by the second micro heater 136b may change, and the refractive index of the second diffraction grating 112b may change according to the change of the temperature of the heat. As a result, the second wavelength of the second light source is changed continuously and stably. According to this embodiment, the multi-distribution feedback laser device can continuously oscillate a first light source of a fixed first wavelength and a second light source of a second wavelength that is continuously changed. The oscillated first and second light sources may be provided to a photomixer via a resonator, thereby generating a terahertz wave that is variable.

According to another embodiment of the present invention, a first heater current may be supplied to the first micro heater 136a and the second micro heater 136b may not be operated. In this case, the first heater current can be continuously changed to continuously oscillate the first light source of the continuously varying first wavelength and the second light source of the fixed second wavelength.

According to another embodiment of the present invention, a first heater current may be supplied to the first micro heater 136a and a second heater current may be supplied to the second micro heater 136b. In this case, the first heater current may be continuously changed, and the second heater current may be continuously changed. Accordingly, the multi-distribution feedback laser device can oscillate the first light source of the first wavelength continuously changing and the second light source of the second wavelength continuously changing. In this case, the temperatures of the heats generated from the first and second micro heaters 136a and 136b may be different so that the wavelengths of the first and second light sources are different.

The present invention is not limited to this. The multi-distribution feedback laser device can be used by various combinations of the above-described methods depending on the requirements of equipment requiring two light sources.

According to the multi-distribution feedback laser device described above, the wavelength difference between the first light source and the second light source oscillated due to the first and second micro heaters 136a and 136b controlled independently of each other may be adjusted. Accordingly, the first and second light sources, which are very stable, can be oscillated. For example, the first and second light sources constitute one compound resonator such that the oscillated first and second light sources are coupled to each other. Therefore, the first and second light sources are not operated as independent light sources, and the phases of the first and second light sources are correlated with each other to obtain a characteristic in which the phase difference is locked. Thus, the multi-distribution feedback laser device can oscillate the first and second light sources which are very stable. As a result, it is possible to implement a multi-distribution feedback laser device with excellent reliability. In the case of terahertz wave generation using the multi-distribution feedback laser device, the RIN (Relative Intensity Noisy) of a beat source whose oscillation frequency, which is a key factor of terahertz wave generation, directly affects stability, is greatly increased. Can be improved.

In addition, the multi-distribution feedback laser device includes a first distribution feedback laser diode of the first distribution feedback area DFB1, a modulation diode of the modulation area P, and a second distribution feedback area DFB2 on the substrate 100. This is mounted. As a result, a highly integrated multi-distribution feedback laser device can be realized.

In addition, the first wavelength of the first light source and the second wavelength of the second light source may be changed by the change of the period of the first diffraction grating 112a and the change of the period of the second diffraction grating 112a, respectively. Can be. Thus, by varying the periods of the diffraction gratings 112a and 112b together with the operation of the micro heaters 136a and 136b, the wavelength difference between the first and second light sources can be more precisely adjusted.

Furthermore, the active layer 106 is formed in the modulation region P as well as the distribution feedback regions DFB1 and DFB2. That is, the active layer 106 is continuously disposed on the substrate 100 of the regions DFB1, P and DFB2. Accordingly, the first light source and the second light source having coherent characteristics can be oscillated continuously. As a result, by generating terahertz waves using the first and second light sources having mutual coherent characteristics, terahertz waves having very stable and excellent characteristics can be generated.

Furthermore, at least one of the diffraction gratings 112a and 112b may be a complex coupled diffraction grating. Accordingly, an output having a very large modulation index can be obtained. As a result, the generation efficiency of terahertz waves generated using the first and second light sources is very high.

Next, a method of forming a multi-distribution feedback laser device according to an embodiment of the present invention will be described with reference to the drawings.

2A to 2H are cross-sectional views illustrating a method of forming a multi-distribution feedback laser device according to an exemplary embodiment of the present invention.

Referring to FIG. 2A, a substrate 100 including a first distributed feedback region DFB1, a modulation region P, and a second distributed feedback region DFB2 is prepared. The lower cladding layer 102 may be formed on the substrate 100. The lower cladding layer 102 is formed on the substrate 100 of the regions DFB1, P and DFB2. The lower cladding layer 102 may be formed of a compound semiconductor doped with a first type dopant. A first separation-limited heterolayer 104 may be formed on the lower cladding layer 102. An active layer 106 may be formed on the first separated hetero layer 104, and a second separated hetero layer 108 may be formed on the active layer 106. The active layer 106 is formed on the substrate 100 of the regions DFB1, P and DFB2. Similarly, the first and second separated hetero layers 104 and 108 are also formed on the substrate 100 of the regions DFB1, P and DFB2.

A first compound semiconductor film 110 is formed on the second separated limited hetero layer 108, and a diffraction grating layer 112 is formed on the first compound semiconductor film 110. The first compound semiconductor film 110 may be formed of indium phosphorus (InP). The first compound semiconductor film 110 may be undoped or doped with a second type dopant. The diffraction grating layer 112 may be formed of a compound semiconductor, for example, InGaAs, for a complex bond diffraction grating. The diffraction grating layer 112 may be doped with an n-type dopant or a p-type dopant. Alternatively, the diffraction grating layer 112 may be in an undoped state.

A buffer compound semiconductor film 114 may be formed on the diffraction grating layer 112. The buffer compound semiconductor film 114 may be formed of the same material as the first compound semiconductor film 110.

Referring to FIG. 2B, a hard mask layer 116 may be formed on the buffer compound semiconductor layer 114. The hard mask layer 116 may include at least one selected from nitride, oxide, oxynitride, and the like.

A photoresist is coated on the hard mask layer 116, and the photoresist is patterned to form photoresist patterns 118. The photoresist layer may be patterned by a holography system or an electron beam lithography apparatus to form the photoresist patterns 118. The photoresist patterns 118 may define diffraction gratings. Periods of the photoresist patterns 118 may be adjusted to control periods of the diffraction gratings.

Referring to FIG. 2C, the hard mask layer 116 may be patterned using the photoresist patterns 118 as an etch mask to form hard mask patterns 116a. The hard mask layer 116 may be etched by magnetically enhanced reactive ion etching. Subsequently, the photoresist patterns 118 may be removed.

Referring to FIG. 2D, the buffer compound semiconductor film 114 and the diffraction grating layer 112 are etched using the hard mask patterns 116a as an etch mask. Accordingly, a first diffraction grating 112a is formed in the first distributed feedback region DFB1, and a second diffraction grating 112b is formed in the second distributed feedback region DFB2. In this case, the remaining grating 112c may be formed in the modulation area P. FIG. Buffer compound semiconductor patterns 114a may be formed on the gratings 112a, 112b, and 112c. An etching process using the hard mask patterns 116a as an etching mask may be isotropic etching (ex, wet etching, etc.) and / or dry etching.

Referring to FIG. 2E, the hard mask patterns 116a are subsequently removed. Subsequently, the remaining grating 112c and the buffer compound semiconductor pattern 114a on the remaining grating 112c in the modulation region P are removed. In this case, the first and second diffraction gratings 112a and 112b and the buffer compound semiconductor patterns 114a on the diffraction gratings 112a and 112b remain in the first and second distribution feedback regions DFB1 and DFB2. do. In order to selectively remove the residual grating 112c, a mask pattern (not shown) by a photolithography process may be used.

Referring to FIG. 2F, a second compound semiconductor film 120 may be formed on the substrate 100. The second compound semiconductor film 120 may be undoped or doped with a second type dopant. The second compound semiconductor film 120 may be formed of the same material as the first compound semiconductor film 120. have. The second compound semiconductor film 120 may be formed by metal organic chemical vapor deposition (MOCVD). The first compound cladding layer 122 may include the first compound semiconductor layer 110, the buffer compound semiconductor pattern 114a and the second compound semiconductor layer 120 of the first and second distributed feedback regions DFB1 and DFB2. Can be configured.

Referring to FIG. 2G, a second upper cladding layer 124 may be formed on the first upper cladding layer 122. The second upper cladding layer 124 may be formed of a compound semiconductor doped with a second type dopant. The second upper cladding layer 124 may be formed of the same compound semiconductor as the first upper cladding layer 124. The first and second upper cladding layers 122 and 124 may be included in the upper cladding layer 125.

An ohmic layer 126 may be formed on the upper cladding layer 125. The ohmic layer 126 may be formed of InGaAs. An electrode film 128 may be formed on the ohmic layer 126. The electrode film 128 may be formed of metal.

Referring to FIG. 2H, the isolation trench 130 may be formed by successively patterning the electrode layer 128, the ohmic layer 126, and the upper cladding layer 125. By the isolation trench 130, a first distribution feedback laser diode of the first distribution feedback region DFB1, a modulation diode of the modulation region P, and a second distribution feedback of the second distribution feedback region DFB2. The laser diodes can be operated independently of one another. By forming the isolation trench 13, the first ohmic pattern 126a and the first electrode 128a in the first distributed feedback region DFB1 and the second ohmic pattern in the second distributed feedback region DFB2 ( 126b and the second electrode 128c, and a third ohmic pattern 126c and a third electrode 128c in the modulation region P may be formed. The electrodes 128a, 128b, 128c are spaced apart from each other. In addition, the ohmic patterns 126a, 126b, and 126c are also spaced apart from each other. An isolation insulating pattern 132 may be formed in the isolation trench 130.

According to an embodiment of the present invention, the isolation trench 130 may be formed by successively patterning the ohmic layer 126 and the upper cladding layer 125 before forming the electrode layer 128. In this case, after the isolation trench 130 and the isolation insulation pattern 132 are formed, the first electrode (1) is formed on the first, second and third ohmic patterns 126a, 126b, and 126c separated from each other. 128a, 128b, and 128c can be formed.

Subsequently, an interlayer insulating film and a heater film are sequentially formed on the first electrode 128a, and the heater film and the interlayer insulating film are successively patterned to form a first interlayer insulating pattern 134a on the first electrode 128a of FIG. And a first micro heater 136a, a second interlayer insulating pattern 134b, and a second micro heater 136b on the second electrode 128b. As a result, the multi-distribution feedback laser device of FIG. 1 may be implemented.

According to an embodiment of the present invention, the heater film may be planarized until the interlayer insulating film is exposed to form the first and second micro heaters 136a and 136b.

1 is a cross-sectional view showing a multi-distribution feedback laser device according to an embodiment of the present invention.

2A to 2H are cross-sectional views illustrating a method of forming a multi-distribution feedback laser device according to an exemplary embodiment of the present invention.

Claims (14)

A substrate comprising a first distributed feedback region, a modulation region, and a second distributed feedback region; An active layer on a substrate of said first distributed feedback, modulation and second distributed feedback regions; A first diffraction grating continuously disposed in the first distributed feedback region and coupled to an active layer of the first distributed feedback region; A second diffraction grating continuously disposed in the second distributed feedback region and coupled to an active layer of the second distributed feedback region; A lower cladding layer interposed between the active layer and the substrate; An upper cladding layer disposed on the active layer; A first electrode electrically connected to an upper cladding layer in the first distributed feedback region; A second electrode electrically connected to an upper cladding layer in the second distributed feedback region; A third electrode electrically connected to an upper cladding layer in the modulation region; Isolation insulating patterns between the first, second, and third electrodes; A first micro heater disposed on the first electrode and supplying heat to the first diffraction grating; A second micro heater disposed on the second electrode and supplying heat to the second diffraction grating, The first micro heater and the second micro heater are controlled independently of each other; A bottom surface of the isolation insulating patterns is lower than a top surface of the upper cladding layer; Supplying a first laser current to the active layer of the first distributed feedback region to oscillate a first light source having a first wavelength, Supplying a second laser current to the active layer of the second distributed feedback region to oscillate a second light source having a second wavelength, And applying a reverse bias to the upper cladding layer, the active layer, and the lower cladding layer of the modulation region to generate a terahertz wave that is varied by generating an electric field absorption phenomenon in the modulation region. The method according to claim 1, The refractive index of the first diffraction grating is changed by heat supplied from the first micro heater, The multidistribution feedback laser device of which the refractive index of the second diffraction grating is changed by heat supplied from the second micro heater. The method according to claim 1, And the temperature of the heat supplied by the first micro heater to the first diffraction grating is different from the temperature of the heat supplied by the second micro heater to the second diffraction grating. The method according to claim 1, The lower cladding layer includes a compound semiconductor doped with a dopant of a first type, and at least an upper portion of the upper cladding layer includes a compound semiconductor doped with a dopant of a second type. delete The method according to claim 4, And the first diffraction grating and the second diffraction grating are disposed in the upper cladding layer. The method according to claim 4, A first separate confinement hetero layer interposed between the lower cladding layer and the active layer and having a bandgap wavelength smaller than that of the active layer; And And a second separation-limited heterolayer interposed between the upper cladding layer and the active and having a smaller bandgap wavelength than the active layer. The method according to claim 4, The first micro heater is disposed above the upper cladding layer of the first distributed feedback region, The second micro heater is disposed above the upper cladding layer of the second distributed feedback region, And the first and second micro heaters are electrically insulated from the upper cladding layer. The method of claim 8, A first interlayer insulating pattern interposed between the first electrode and the first micro heater; And The multi-distribution feedback laser device further comprises a second interlayer insulating pattern interposed between the second electrode and the second micro heater. The method according to claim 1, And at least one of the first diffraction grating and the second diffraction grating is a complex coupled diffraction grating. The method according to claim 1, The active layer is a multi-distribution feedback laser device formed of a multi-quantum well structure. The method according to claim 1, And a period of the first diffraction grating and a period of the second diffraction grating are the same. The method according to claim 1, And a period of the first diffraction grating and a period of the second diffraction grating are different from each other. The method according to claim 1, And the first and second diffraction gratings comprise a compound semiconductor doped with an n-type or p-type dopant.

Images