WO2022110914A1 - Resonant cavity, laser unit, laser and laser radar - Google Patents

Abstract

A resonant cavity, a laser unit, a laser and a laser radar. The resonant cavity comprises a first reflector and a second reflector provided at intervals and opposite to each other; and an active structure located between the first reflector and the second reflector. The active structure comprises one or more first active areas and one or more second active areas, the material of the first active areas has tensile strain, and the material of the second active areas has compressive strain. The second active areas having compressive strain has higher gain and can regulate a bandgap to adjust the working band. The first active areas having tensile strain can release the compressive strain introduced in the second active areas, to prevent stress accumulation and avoid stress relief. The provision of the first active areas and the second active areas can realize stress balance and inhibit the generation of structural defects while ensuring the gain of the active structure, which facilitates improving the quality of the resonant cavity, the external quantum efficiency and power, and the reliability of a device.

Description

Resonators, Laser Units, Lasers and Lidars

This application claims the priority of the Chinese patent application filed on November 25, 2020 with the application number 202011344323.4 and the invention titled "Resonator, Laser Unit, Laser and Lidar", the entire contents of which are incorporated herein by reference Applying.

technical field

The invention relates to the field of lasers, in particular to a resonant cavity, a laser unit, a laser and a laser radar.

Background technique

Lidar is a commonly used ranging sensor, which has the characteristics of long detection distance, high resolution, and little environmental interference. It is widely used in intelligent robots, unmanned aerial vehicles, unmanned vehicles and other fields. In recent years, autonomous driving technology has developed rapidly, and lidar, as the core sensor of its distance perception, has become indispensable. Laser, as one of the core components of lidar, its performance has a great influence on the performance of lidar.

The traditional vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser, referred to as VCSEL) usually includes a lower layer Bragg reflector (Distributed Bragg Reflector, referred to as DBR), an active region, and a current confinement layer, which are sequentially epitaxially grown on an N-type doped substrate. and the upper layer DBR. Among them, the current is injected into the active area through the electrode; the material in the active area is excited by the light, and resonates in the resonant cavity formed by the upper DBR and the lower DBR, forming a strong beam with the same propagation direction, frequency and phase.

In a VCSEL, the active region is a quantum well (Multi Quantum Wells, MQWs) formed by alternately growing thin films of two materials. In the active region using quantum wells, structural strain is often introduced, so as to achieve the purpose of improving the gain of the active region and regulating the energy band of the quantum well.

However, the introduction of strain increases the risk of lattice structure defects, resulting in reduced external quantum efficiency and power or reduced device reliability.

SUMMARY OF THE INVENTION

The problem solved by the present invention is to provide a resonator, laser unit, laser and lidar to overcome the problems caused by strain introduction.

In order to solve the above problems, the present invention provides a resonant cavity, comprising:

a first reflection mirror and a second reflection mirror, the first reflection mirror and the second reflection mirror are arranged at a relative interval; an active structure, the active structure is located at the first reflection mirror and the second reflection mirror between; the active structure includes one or more first active regions and one or more second active regions, the material of the first active regions has tensile strain, the second active regions The material has compressive strain.

Optionally, at least one of the first active region and the second active region is a quantum well active region, and the quantum well active region includes a barrier region and a barrier region located between adjacent barrier regions. Potential well region.

Optionally, the first active region includes: an overcompensated quantum well, and the second active region includes: a compressively strained quantum well.

Optionally, the material of the potential well region of the first active region has compressive strain, and the material of the barrier region of the first active region has tensile strain; the stress magnitude of the tensile strain of the material of the barrier region of the first active region is The stress is greater than the compressive strain of the material of the potential well region of the first active region.

Optionally, the material of the well region of the first active region is InGaAs, and the material of the barrier region of the first active region is at least one of GaAsP and AlGaAsP.

Optionally, the material of the potential well region of the second active region has compressive strain, the material of the barrier region of the second active region has compressive strain, and the stress magnitude of the compressive strain of the material of the barrier region of the second active region is smaller than that of the second active region. The stress magnitude of the compressive strain of the material of the potential well region of the active region.

Optionally, the material of the well region of the second active region is InGaAs, and the material of the barrier region of the second active region is AlGaAs.

Optionally, the material of the potential well region of the second active region has compressive strain, and the material of the potential barrier region of the second active region has no strain.

Optionally, the quantum well active region includes multiple quantum wells.

Optionally, the material of the first reflector includes N-type doped ions; and one of the first active regions is located on the surface of the first reflector.

Optionally, it further includes: a reflective layer, the reflective layer is located between the adjacent first active regions and the second active regions.

Optionally, the first active region is located on one side of the reflective layer, and the one or more second active regions are located on the other side of the reflective layer.

Optionally, the refractive index of the reflective layer material is different from the refractive index of the first active region material, and the refractive index of the reflective layer material is different from the refractive index of the second active region material .

Optionally, the reflection layer is a distributed Bragg mirror.

Optionally, the reflective layer is a laminated structure, the reflective layer includes a first reflective sub-layer and a second reflective sub-layer, the refractive index of the first reflective sub-layer and the refractive index of the second reflective sub-layer rates are not equal.

Optionally, the first reflection sublayers and the second reflection sublayers are alternately arranged.

Optionally, the active region has a first surface and a second surface opposite to each other, and the direction of the first surface pointing to the second surface is consistent with the current direction; the resonant cavity further includes: a current confinement layer, the current confinement layer A layer is located on at least the first surface.

Optionally, the current confinement layer is provided on the surface of the first active region facing the second active region.

Optionally, the method further includes: a substrate, where the substrate is located on a side of the first mirror away from the active structure.

Optionally, the substrate is an N-type substrate, the dopant ions contained in the first mirror are N-type ions, and the dopant ions contained in the second mirror are P-type ions.

Correspondingly, the present invention provides a laser unit, comprising:

A resonant cavity, the resonant cavity is the resonant cavity of the present invention; a first electrode; and a second electrode.

Optionally, the second electrode is located on a surface of the second mirror on a side away from the active structure.

Optionally, the first electrode is located on a side of the first mirror away from the active structure, and the first electrode is located on the surface of the substrate.

Optionally, the second electrode includes a window, and the window penetrates the second electrode along the laser propagation direction.

In addition, the present invention also provides a laser, comprising:

A laser unit, the laser unit is the laser unit of the present invention.

Optionally, the laser is a vertical cavity surface emitting laser.

In addition, the present invention also provides a laser radar, comprising:

A light source comprising the laser of the present invention.

Compared with the prior art, the technical solution of the present invention has the following advantages:

In the technical solution of the present invention, the active structure includes a first active region and a second active region, wherein the material of the first active region has tensile strain, and the material of the second active region has compressive strain. The first active region with tensile strain can release the compressive stress introduced by the second active region, preventing stress accumulation and avoiding stress release; therefore, the arrangement of the first active region and the second active region can While ensuring the gain of the active structure, achieving stress balance and suppressing the generation of structural defects is conducive to improving the quality of the resonator cavity, improving the external quantum efficiency and power, and improving the reliability of the device.

In an optional solution of the present invention, at least one of the first active region and the second active region is a quantum well active region, and the quantum well active region includes a barrier region and an adjacent barrier region. The potential well region between, that is to say, the first active region and the second active region are similar in structure, so the arrangement of the first active region and the second active region will Increasing the structural complexity of the active structure eliminates the need to analyze and optimize factors such as resistance, energy band, diffusivity, and defect generation, which can greatly reduce the complexity of the stress-balanced active structure design.

In an optional solution of the present invention, the first active region includes: an overcompensated quantum well, and the second active region includes: a compressively strained quantum well. By setting the overall structure of the quantum wells of the first active region and the second active region to different strain forms, the selection range of quantum well materials can be expanded while satisfying the stress balance, avoiding the limitation of the working wavelength, and ensuring the potential The barrier height is increased, and the gain of the active area is improved.

In an optional solution of the present invention, the material of the well region of the first active region has compressive strain, the material of the barrier region of the first active region has tensile strain; the material of the barrier region of the first active region has tensile strain The magnitude of the stress is greater than the stress magnitude of the compressive strain of the material of the potential well region of the first active region, so that the entire material of the first active region exhibits tensile strain, corresponding to the accumulation of tensile stress, so as to realize the The balance of compressive strain in the second active region; and the larger tensile strain in the barrier region of the first active region tends to have a higher barrier height. Compared with the barrier region of compressive strain, the formed quantum well has Stronger quantum confinement effect, can obtain greater gain.

In an optional solution of the present invention, the material of the well region of the second active region has compressive strain, the material of the barrier region of the second active region has compressive strain, and the stress of the compressive strain of the material of the barrier region of the second active region The stress size is smaller than the compressive strain of the material of the potential well region of the second active region, that is, the barrier region of the second active region adopts a material with no stress or a small amount of compressive stress, and the entire second active region is compressive strain to obtain more stress. high gain.

In an optional solution of the present invention, the material of the first reflector includes N-type doped ions; and one of the first active regions is located on the surface of the first reflector. The material of the first mirror with N-type doped ions has compressive strain, so directly disposing the first active region with tensile strain on the first mirror can make the first active region with tensile strain to balance part compressive strain of the first mirror to avoid compressive stress accumulation.

In an optional solution of the present invention, it further includes: a reflective layer, the reflective layer is located between the adjacent first active regions and the second active regions, and the setting of the reflective layer can adjust the cavities of different active regions of the resonator cavity Therefore, the gain difference can be balanced, so that the two active regions can work under suitable conditions, and the device performance can be further improved.

In an optional solution of the present invention, the reflection layer is a distributed Bragg mirror. Since the first reflector and the second reflector are generally Bragg reflectors, the reflector layers are set to be the same Bragg reflector without introducing additional structures, thereby reducing the impact of introducing reflector layers on structural complexity.

In an optional solution of the present invention, the current confinement layer is provided on the surface of the first active region facing the second active region. Since the material of the current confinement layer has compressive strain, the first active region can balance the compressive strain of part of the current confinement layer, thereby reducing the influence of the current confinement layer on the compressive strain of the second active region.

In an optional solution of the present invention, the resonant cavity further includes a substrate, and the substrate is located on the side of the first reflector away from the active structure; the substrate is an N-type substrate, and the first reflector The dopant ions contained in the mirror are N-type ions, and the dopant ions contained in the second mirror are P-type ions. The material quality of the N-type substrate is high, which can provide a good growth surface for the formation of the resonant cavity to ensure the quality of the resonant cavity.

Description of drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

1 is a schematic diagram of a cross-sectional structure of a VCSEL unit;

FIG. 2 is a schematic cross-sectional structure diagram of another VCSEL unit;

Fig. 3 is the energy band structure schematic diagram of quantum well;

FIG. 4 is a schematic diagram of the change of the lattice structure before and after the introduction of strain during epitaxial growth;

5 is a schematic cross-sectional structure diagram of an embodiment of a resonant cavity of the present invention;

6 is a schematic cross-sectional structure diagram of another embodiment of the resonator cavity of the present invention;

FIG. 7 shows the distribution of the light field intensity in the resonator cavity in the embodiment shown in FIG. 6 without arranging a reflective layer;

Fig. 8 shows the distribution of the light field intensity in the resonator cavity in the embodiment shown in Fig. 6;

Fig. 9 is the distribution situation of the light field intensity in the cavity in another embodiment of the resonant cavity of the present invention;

Fig. 10 is the distribution situation of the light field intensity in the cavity in yet another embodiment of the resonant cavity of the present invention;

11 is a schematic cross-sectional structure diagram of another embodiment of the laser unit of the present invention;

FIG. 12 is a schematic cross-sectional structure diagram of another embodiment of the laser unit of the present invention.

Detailed ways

As known from the background art, the introduction of strain into the active region of a VCSEL increases the risk of lattice structure defects. Now combined with the structure of VCSEL to analyze the reasons for the increased risk of lattice structure defects:

Referring to FIG. 1 , a schematic cross-sectional structure diagram of a VCSEL unit is shown.

The VCSEL laser chip includes a plurality of VCSEL units. As shown in FIG. 1, between the upper electrode 15 and the ring-shaped lower electrode 16, the device structure of the VCSEL unit includes: a lower layer DBR 11, an active region 12, a current confinement layer 13 and an epitaxially grown on the substrate 10 in sequence. Upper DBR 14. Each epitaxial layer is epitaxial on the substrate 10 (at least one of GaAs substrate, doped Si substrate and doped C substrate) by metal-organic chemical vapor deposition (Metal-Organic Chemical Vapour Deposition, MOCVD) technology growth obtained.

In each VCSEL unit, the current is injected into the active region 12 through the upper electrode 15; the material of the active region 12 is excited by the light, and resonates in the resonant cavity formed by the upper DBR 14 and the lower DBR 11 to form a propagation direction A consistent, intense beam of frequency and phase. Figure 1 shows a front light emitting VCSEL unit, in which the upper DBR 14 has fewer cycles, and the reflectivity is slightly lower than that of the lower DBR 11, so that part of the light is transmitted upward from the upper DBR 14 and becomes a usable laser.

Referring to FIG. 2 , a schematic cross-sectional structure diagram of another VCSEL unit is shown.

Similarly, a lower layer DBR 21 , an active region 22 , a current confinement layer 23 and an upper layer DBR 24 are sequentially epitaxially grown on the substrate 20 . Figure 2 shows a backside light-emitting VCSEL unit, so the upper layer electrode 25 is prepared on the top layer of the upper layer DBR 24 of each VCSEL unit, and the annular lower layer electrode 26 is prepared at the bottom of the VCSEL laser chip. Compared with the front light emitting VCSEL, the laser light of the back light emitting VCSEL is emitted from the substrate 20 .

Regardless of whether it is a front light emitting VCSEL or a back light emitting VCSEL, the active regions 12 and 22 are quantum wells formed by alternately growing thin films of two materials. Specifically, the active regions 12 and 22 include small band gap semiconductor films and large band gap semiconductor films, and the small band gap semiconductor films and the large band gap semiconductor films are alternately arranged in the active regions 12 and 22 to form quantum well structure. After the quantum well structure is formed, a layer of Al _1-x Ga x As is formed on the surfaces of the active regions 12 and 22; a circular hole is formed in the Al _{1-x Ga x As} layer by chemical wet etching. ; After that, the formed structure is subjected to oxidation treatment on the Al _1-x Ga _x As layer under a high temperature wet nitrogen environment, so that part of the Al _1-x Ga _x As layer is converted into Al _1-x Ga _xO insulating layers to form the current confinement layers 13 and 23 . In the current confinement layers 13 and 23, the circular holes obtained by the chemical wet etching method are used to form the current injection window, and the Al _1-x Ga _x O insulating layer limits the current injected through the upper electrode 15. effect. In Al _1-x Ga _x As, preferably x≤0.04, that is, a high Al composition, which can ensure a higher oxidation rate.

Referring to Figure 3, a schematic diagram of the band structure of the quantum well is shown.

In the active region of the quantum well structure, a small-band-gap semiconductor thin film is arranged between two adjacent large-band-gap semiconductor thin films. Therefore, the conduction band and valence band of the quantum well structure exhibit the well-like potential shown in FIG. 3 . Among them, the region of the small band gap film between two adjacent large band gap semiconductor films is called the well region, and the region of the large band gap semiconductor film on both sides of the small band gap semiconductor film is called the potential barrier (Barrier) area.

Referring to FIG. 4, a schematic diagram of the lattice structure change before and after strain introduction during epitaxial growth is shown.

During the epitaxial growth of the semiconductor structure, when the lattice constant of the material of the epitaxial layer formed is different from that of the growth surface (for example, the lattice constant of the material of the growth layer is different from that of the substrate), the epitaxy formed Strain is created in the layer and stress is introduced.

As shown in FIG. 4 , when the lattice constant of the formed epitaxial layer material is larger than the lattice constant of the growth surface (for example, when the lattice constant of the growth layer material is larger than that of the substrate material), the epitaxial layer is formed Compressive strain will be generated, and the lattice constant of the formed epitaxial layer will be squeezed to the lattice constant of the growth surface. Correspondingly, compressive stress will be generated in the formed epitaxial layer; on the contrary, the formed epitaxial layer material When the lattice constant of the epitaxial layer is smaller than the lattice constant of the growth surface (for example, when the lattice constant of the growth layer material is smaller than the lattice constant of the substrate material), tensile strain will be generated in the formed epitaxial layer, so The lattice constant of the formed epitaxial layer is stretched to be close to the lattice constant of the growth surface, and accordingly, tensile stress is generated in the formed epitaxial layer.

Compressive strain is often introduced in the active region of the quantum well structure. Because the introduction of compressive strain can tune the energy band shape of the quantum well region; compared with the introduction of tensile strain, the quantum well structure with compressive strain can obtain higher gain in the active region, thereby simultaneously adjusting the size of the band gap to tune the corresponding work wavelength of light.

However, the introduction of strain also has its disadvantages. As mentioned above, the introduction of strain will generate stress in the formed epitaxial layer, and the stress will accumulate with the growth of the epitaxial layer. When the energy accumulated in the stress is large enough, stress release will occur, resulting in structural defects such as dislocations in the formed epitaxial layer.

If structural defects are formed in the active area, the non-radiative coincidence of electron-hole pairs in the active area will be increased, resulting in a decrease in external quantum efficiency (EQE) and power; if structural defects are formed in the active area In areas outside the region, in aging experiments or practical applications, structural defects will grow and diffuse into the active region, resulting in reduced device reliability.

For EQE, the differential external quantum efficiency η _d (Differential External Quantum Efficiency) can be used to measure,

Structural defects will trap carriers and cause heat generation without generating photons, resulting in the increase of the amount of photons received and the decrease of EQE.

Therefore, it is often necessary to balance the stress while forming the strain-introduced quantum well structure active region. There are two main ways to balance stress:

One way is to have a separate stress relief layer.

In the vicinity of the quantum well structure, an epitaxial layer with opposite strain is added, for example, a release layer for introducing tensile strain is arranged in the vicinity of the quantum well structure in which compressive strain is introduced, so as to release the compressive stress. However, the introduction of a stress release layer will increase the complexity of the structure, and it is necessary to analyze and optimize the release layer separately for factors such as resistance, energy band, diffusion, and defect generation. This will greatly increase the complexity of the design.

Another way is to set the potential well and the potential barrier of the quantum well into different strain forms when designing the quantum well.

As mentioned earlier, in order to obtain higher gain, the well region is generally set to compressive strain, so the barrier region is set to tensile strain to balance the stress generated by the well region. The advantage of this approach is that the quantum well structure can achieve stress balance within the range of epitaxial growth, thereby ensuring the growth quality of the formed quantum well structure and improving the reliability of the device.

However, in order to meet the stress balance condition, the material selection range of the barrier region is limited, which will limit the operating wavelength conditions of the formed laser; and the tensile strained barrier region usually has a smaller band gap, and the corresponding barrier height is relatively small. small, resulting in low gain in the active region and sacrificing the performance of the device.

In order to solve the technical problem, the present invention provides a resonant cavity, a laser unit and a laser, comprising: a first reflection mirror and a second reflection mirror, the first reflection mirror and the second reflection mirror are relatively spaced apart; an active structure, the active structure is located between the first mirror and the second mirror; the active structure includes one or more first active regions and one or more second active regions , the material of the first active region has tensile strain, and the material of the second active region has compressive strain.

The active structure includes a first active region and a second active region, wherein the material of the first active region has tensile strain and the material of the second active region has compressive strain. The first active region with tensile strain can release the compressive stress introduced by the second active region, preventing stress accumulation and avoiding stress release; therefore, the arrangement of the first active region and the second active region can While ensuring the gain of the active structure, achieving stress balance and suppressing the generation of structural defects is conducive to improving the quality of the resonator cavity, improving the external quantum efficiency and power, and improving the reliability of the device.

In order to make the above objects, features and advantages of the present invention more clearly understood, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Referring to FIG. 5 , a schematic cross-sectional structure diagram of an embodiment of a resonant cavity of the present invention is shown.

As shown in FIG. 5 , the resonant cavity includes: a first reflection mirror 110 and a second reflection mirror 140 , the first reflection mirror 110 and the second reflection mirror 140 are arranged relatively spaced apart; an active structure (not shown in the figure) mark), the active structure is located between the first mirror 110 and the second mirror 140; the active structure includes one or more first active regions 121 and one or more second In the active regions 122a, 122b, the material of the first active region 121 has tensile strain, and the material of the second active region 122a, 122b has compressive strain.

The first active region 121 with tensile strain can release the compressive stress introduced by the first mirror 110 and the second active regions 122a, 122b, prevent stress accumulation, and avoid stress release during device operation and reduce service life; The arrangement of the first active region 121 and the second active regions 122a, 122b can achieve stress balance while ensuring the gain of the active structure, suppress the generation of structural defects, and is conducive to improving the quality of the resonant cavity and improving the External quantum efficiency and power are beneficial to improve device reliability.

It should be noted that, in this embodiment, the resonant cavity is a resonant cavity of a vertical cavity surface emitting laser.

Embodiments of the technical solutions of the present invention will be described in detail below with reference to the accompanying drawings.

The first reflecting mirror 110 and the second reflecting mirror 140 which are arranged at opposite intervals serve as two reflecting surfaces of the resonant cavity respectively, and light travels back and forth between the first reflecting mirror 110 and the second reflecting mirror 140 .

In some embodiments of the present invention, the first reflector 110 and the second reflector 140 are Bragg reflectors (Distributed Bragg Reflector, DBR for short), and the first reflector 110 and the second reflector 140 Both include high-refractive-index films and low-refractive-index films, and high-refractive-index films and low-refractive-index films are alternately arranged. The adjacent high-refractive-index films and low-refractive-index films constitute a period. The reflectivity of a distributed Bragg mirror is related to the number of periods of the high and low refractive index films in it. For example, the first reflecting mirror 110 and the second reflecting mirror 140 may be AlxGa1 _{- xAs} /Al1 _{- yGayAs} thin films arranged alternately in sequence, wherein the values of x and y may be different.

In order to ensure the gain of the resonant cavity, the first mirror 110 and the second mirror 140 must have a comparable number of periods to meet the requirement of high reflectivity. In addition, in order to ensure that the outgoing laser light has a narrow line width, after the light is repeatedly reflected by the first reflecting mirror 110 and the second reflecting mirror 140, a standing wave is formed in the resonant cavity. Therefore, the first reflecting mirror 110 and the second reflecting mirror 140 need to have comparable reflectivity.

In this embodiment, the reflectivity of the first reflector 110 is greater than or equal to 99.9%, and the number of periods of the first reflector 110 is greater than or equal to 30, so as to meet the requirement of high reflectivity of the resonant cavity; the second reflector The reflectivity of the reflecting mirror 140 is greater than or equal to 98%, and the period number of the second reflecting mirror 140 is greater than or equal to 11. Ensuring the overall number of periods of the first reflecting mirror 110 and the second reflecting mirror 140 can ensure that the first reflecting mirror 110 and the second reflecting mirror 140 meet the requirements of high reflectivity to form a resonant cavity, which can ensure that the resonating cavity is gain to ensure the luminous intensity.

It should be noted that, in this embodiment, the reflectivity of the second reflector 140 is lower than the reflectivity of the first reflector 110 , so the first reflector 110 points to the direction of the second reflector 140 The direction is the same as the laser exit direction. The reflectivity of the first reflecting mirror 110 is set to be higher than 99.9%, so as to avoid the loss of light energy caused by the transmission of the generated laser light as much as possible.

The active structure has a gain medium capable of realizing particle number inversion, thereby generating stimulated radiation amplification.

In some embodiments of the present invention, at least one of the first active region 121 and the second active regions 122a and 122b is a quantum well active region, and the quantum well active region includes a barrier region and a A potential well region between adjacent barrier regions.

The structures of the first active region 121 and the second active regions 122a and 122b are similar. Therefore, the arrangement of the first active region 121 and the second active regions 122a and 122b will not increase the number of active regions. The structural complexity of the structure does not require separate analysis and optimization of factors such as resistance, energy band, diffusivity, defect generation, etc., which can greatly reduce the complexity of stress-balanced active structure design.

In this embodiment, the resonant cavity is a resonant cavity of a vertical cavity surface emitting laser. For vertical cavity surface emitting lasers, in order to improve the gain of the quantum well active region, the quantum well structure is usually set at the antinode position of the standing wave of the optical field; in order to further enhance the overall gain of the laser and achieve high power output, in multiple waves One or more quantum wells (Quantum Well or Multi Quantum Wells, QW or MQWs) are respectively set at the position of the abdomen. Specifically, the quantum well active region includes a plurality of quantum wells. In this embodiment, each of the first active region 121 and the second active region 122a and 122b in the active structure has a The source regions are all structures of multiple quantum wells.

It should be noted that a quantum well at an antinode position is equivalent to a PN junction; the active structure is equivalent to a series of multiple PN junctions. The potential barrier between N-P increases the resistance of the active structure. In order to reduce the resistance, the resonant cavity further includes: a tunneling layer, and the tunneling layer is located between adjacent active regions.

In this embodiment, the resonant cavity includes a first tunneling layer 151 located between the first active region 121 and the second active region 122a, and a first tunnel layer 151 located between the second active region 122a and the second active region 122a and the second active region 122a. The second tunneling layer 152 between the active regions 122b.

Therefore, tunneling is formed between the adjacent first active regions 121 and the second active regions 122a and between the adjacent second active regions 122a and the second active regions 122b Junction (Tunnel Junction), through the reverse biased tunnel junction, can effectively reduce the connection resistance between adjacent active regions.

It should also be noted that, in order to adjust the position of the quantum well structure so that it is located at the antinode position of the standing wave of the optical field, the resonant cavity further includes: a space-filling layer, the space-filling layer is located between adjacent quantum well active regions . In this embodiment, the resonant cavity includes a first void-filling layer 171 and a second void-filling layer 172 located between adjacent active regions, wherein the first void-filling layer 171 is located between the first active region 121 and the second void-filling layer 172 Between the two active regions 122a, the second void filling layer 172 is located between the second active region 122a and the second active region 122b.

In some embodiments of the present invention, the first active region 121 includes: an over-compensated quantum well (Over-Compensated QW), and the second active regions 122a, 122b include: a compressive strain quantum well (Compressive Strain QW) ). By setting the overall structure of the quantum wells of the first active region 121 and the second active regions 122a, 122b into different strain forms, the selection range of quantum well materials can be expanded while satisfying the stress balance, avoiding the limitation of the working wavelength, It can also ensure the height of the potential barrier and improve the gain of the active region.

In this embodiment, the material of the well region of the first active region 121 has compressive strain, and the material of the barrier region of the first active region 121 has tensile strain; the tensile strain of the material of the barrier region of the first active region 121 The stress magnitude of the strain is greater than the stress magnitude of the compressive strain of the material of the potential well region of the first active region 121 . Since the tensile stress of the barrier region of the first active region 121 is greater than the compressive stress of the well region of the first active region 121, the entire first active region 121 is in a state of tensile strain, which is called excessive stress. Compensated quantum well. Corresponding to the accumulation of tensile stress, the first active region 121 that exhibits tensile strain as a whole can achieve a certain balance of compressive strain, which can effectively reduce the stress accumulation of the active structure; and the first active region 121 is a barrier region. Larger tensile strains tend to have higher barrier heights, and the resulting quantum wells have stronger quantum confinement effects than compressive strained barrier regions, resulting in greater gains.

In this embodiment, the material of the well region of the second active regions 122a and 122b has compressive strain, the material of the barrier region of the second active regions 122a and 122b has compressive strain, and the material of the barrier regions of the second active regions 122a and 122b has compressive strain. The stress magnitude of the compressive strain of the material is smaller than the stress magnitude of the compressive strain of the material of the potential well regions of the second active regions 122a and 122b. Specifically, the barrier regions of the second active regions 122a and 122b are made of materials with a small amount of compressive stress. In other embodiments of the present invention, the material of the well region of the second active region has compressive strain, and the material of the barrier region of the second active region has no strain. The barrier region of the second active region adopts a material with little or no compressive stress, and the entire second active region is compressively strained to obtain higher gain.

Specifically, for a resonant cavity with GaAs as a substrate, based on the working band of the resonant cavity, the material of the potential well region of the first active region 121 is one of InGaAs, GaAs, InGaAsN, and InGaAsNSb, and the first active region 121 is made of InGaAs, InGaAsN, and InGaAsNSb. The material of the barrier region of the first active region 121 is one of GaAsP, AlGaAsP, AlGaAsN and GaAsN; the material of the potential well region of the second active region 122a and 122b is one of InGaAs, GaAs, InGaAsN and InGaAsNSb. The material of the barrier regions of the two active regions 122a and 122b is AlGaAs or GaAs.

It should be noted that, in this embodiment, the material of the first reflecting mirror 110 includes N-type doping ions; one of the first active regions 121 is located on the surface of the first reflecting mirror 110 . The material of the first mirror 110 has compressive strain, so the first active region 121 with tensile strain is directly disposed on the surface of the first mirror 110, which can balance the tensile strain of the first active region 121 as described in part. compressive strain of the first mirror 110 to avoid compressive stress accumulation.

In addition, in some embodiments of the present invention, the active region has a first surface and a second surface opposite to each other, and the direction of the first surface pointing to the second surface is consistent with the current direction; the resonant cavity further includes: a current confinement layer , the current confinement layer is located at least on the first surface. The current confinement layer can limit the distribution range of the current and suppress the current dispersion effect, thereby increasing the current density of the light-emitting region in the active region to improve the gain.

Furthermore, in some embodiments of the present invention, the current confinement layer is provided on the surface of the first active region facing the second active region. Since the material of the current confinement layer has compressive strain, the first active region can balance the compressive strain of part of the current confinement layer, and the current confinement layer is formed by oxidation, and oxidation will bring about strong forming the current confinement layer on the surface of the first active region can also reduce the influence of the oxidation process on the subsequent second active region, and reduce the compressive strain of the oxidation process affecting the second active region.

Specifically, in this embodiment, the resonant cavity includes three current confinement layers: a first current confinement layer, a second current confinement layer, and a third current confinement layer. In this embodiment, the material of the first reflecting mirror 110 includes N-type doping ions, the second reflecting mirror 140 includes P-type doping ions, and the direction of the second reflecting mirror 140 pointing to the first reflecting mirror 110 is the same as that of the first reflecting mirror 110 . The current direction is the same; therefore, the direction in which the second mirror 140 points to the first mirror 110 is the same as the direction in which the first surface points to the second surface, and the surface of the active region facing the second mirror 140 is the first surface, The direction of the active region toward the first mirror 110 is the second surface. For example, the surface of the first active region 121 facing the second mirror 140 is the first surface 1211 of the first active region 121 , and the surface of the first active region 121 facing the first mirror 110 is the second surface 1212 of the first active region 121 . The first and second surfaces of the second active regions 122a and 122b are arranged in the same order as the first surfaces 1211 and 1212 of the first active region 121 , that is, toward the second reflection The surface of the mirror 140 is the first surface, and the surface facing the first reflecting mirror 110 is the second surface, which is not repeated here in the present invention. Therefore, the first current confinement layer, the second current confinement layer and the third current confinement layer are respectively located on the first surface 1211 of the first active region 121 and the second active region 122a the first surface and the first surface of the second active region 122b.

In addition, in this embodiment, in order to simplify the process steps and improve the quality of materials, in the process of forming the current confinement layer, after the growth of all materials is completed, the semiconductor compound is oxidized, that is, as shown in FIG. 5 . In an embodiment, after the second mirror 140 is formed, the semiconductor compound used to form the current confinement layer is oxidized; therefore, only the semiconductor compound layer used to form the current confinement layer is shown in FIG. 5 . Specifically, the resonant cavity includes a first semiconductor compound 131 located on the first surface 1211 of the first active region 121, a second semiconductor compound 132 located on the first surface of the second active region 122a, and the second semiconductor compound 132. The third semiconductor compound 133 on the first surface of the active region 122b. However, this method is only an example. In other embodiments of the present invention, the resonant cavity may be formed by means of secondary epitaxy, that is, after the semiconductor compound is formed, the machine is replaced and the step of oxidizing is performed. Not limited.

It should also be noted that, in some embodiments of the present invention, the resonant cavity further includes: a substrate 100, where the substrate 100 is located on the side of the first mirror 110 away from the active structure, or all the The substrate 100 is located on the side of the second mirror 140 away from the active structure.

The substrate 100 can provide a process platform during the formation of the resonant cavity. In this embodiment, the substrate 100 is located on the side of the first mirror 110 away from the active structure. Therefore, in the process of forming the resonant cavity, after the substrate 100 is provided, the first mirror 110 , the active structure and the second mirror 140 are sequentially formed on the substrate 100 .

The material of the substrate may be one of N, P-type doped GaAs, InP, GaSb or InSb. Specifically, the substrate 100 is an N-type substrate, that is, the material of the substrate 100 is an N-type doped semiconductor material (for example, one of N-type doped GaAs, InP, GaSb or InSb), The dopant ions contained in the first reflecting mirror 110 are N-type ions, and the dopant ions contained in the second reflecting mirror 140 are P-type ions. Since the substrate technology of N-type doped semiconductor material is relatively mature and the material quality is relatively high, the method of setting the material of the substrate 100 to be an N-type doped semiconductor material (eg N-type doped GaAs) , which can provide a good growth surface and process platform for the subsequent growth of the first reflecting mirror 110 , the active structure and the second reflecting mirror 140 , and can effectively improve the quality of the subsequent material film layers.

It should be noted that, in this embodiment, the substrate 100 is a GaAs substrate. In other embodiments of the present invention, the substrate may also be other semiconductor materials. When the substrate is made of other semiconductor materials, the material of the active structure can be selected according to the material of the substrate to achieve stress balance.

It should be noted that, in this embodiment, the number of the first active regions 121 is one; the number of the second active regions is two. However, the present invention does not limit the number of the first active region and the second active region. In other embodiments of the present invention, the number of the first active region may also be 2-4, and the second active region The number of zones can also be 1-3. For example, when the gain of the second active region is higher than that of the first active region, a larger number of the second active region can be provided to improve the overall gain and output power of the resonant cavity.

It should also be noted that, in this embodiment, one first active region 121 and two second active regions 122a and 122b are sequentially formed on the substrate 100 . But this setup is just an example. In other embodiments of the present invention, the second active region is located between adjacent first active regions. For example, in other embodiments of the present invention, the first active region, the first active region, the An active structure in which the two active regions and the first active region are sequentially arranged.

Referring to FIG. 6 , a schematic cross-sectional structure diagram of another embodiment of the resonator cavity of the present invention is shown.

The resonant cavity includes: a first mirror 210, a first active region 221, two second active regions 222a, 222b, and a second mirror 240, which are sequentially located on the substrate 200; The first current confinement layer 231, the first void-filling layer 271 and the first tunneling layer 251 between the source region 221 and the second active region 222a; located in the second active region 222a and the second The second current confinement layer 232, the second void filling layer 272 and the second tunneling layer 252 between the active regions 222b; the third current confinement on the surface of the second active region 222b facing the second mirror 240 Layer 233.

This embodiment is the same as the previous embodiment, which is not repeated in the present invention. As shown in FIG. 6 , the difference between this embodiment and the previous embodiment is that in this embodiment, the resonant cavity further includes: A reflective layer 280, the reflective layer is located inside the active structure. The setting of the reflective layer 280 can adjust the cavity loss of different active regions in the resonator active structure, so as to balance the gain difference, so that the two active regions in the active structure can work under suitable conditions, The device performance can be further improved.

It should be noted that, in this embodiment, a current confinement layer is also provided on the active region. Specifically, as shown in FIG. 6 , the reflective layer 280 is located between the first current confinement layer 231 and the first current confinement layer 231 between the source regions 221; in other embodiments of the present invention, the reflective layer may also be disposed on the side of the first current confinement layer away from the first active region, that is, the first current confinement layer is located on the side of the first current confinement layer. between the reflective layer and the first active region.

In some embodiments of the present invention, the active structure is divided into two parts, and the two parts of the active structure are located on two sides of the reflective layer 280 respectively on a straight line along the light propagation direction. In this embodiment, the reflective layer 280 is located between the adjacent first active regions 221 and the second active regions 222a, that is, the first active region 221 in the active structure is located in the reflective layer 280 One or more of the second active regions 222a, 222b in the active structure are located on the other side of the reflective layer.

As shown in FIG. 6 , the first active region 221 is located on the side of the reflection layer 280 facing the first reflection mirror 210 , and the second active regions 222 a and 222 b are located on the side of the reflection mirror 280 facing the first reflection mirror 210 in sequence. one side of the second mirror 240.

Since the material of the first active region 221 and the material of the second active region 222a, 222b are of different strain types, the first active region 221 and the second active region 222a, 222b of the quantum well structure 222b adopts different types of junction designs, and the gains of the quantum wells of different junction designs are different. The setting of the reflective layer 280 can balance the gain difference of the quantum wells of different junction designs, and can further improve the device performance.

The effect of the reflective layer 280 to balance the gain difference of the quantum wells of different junction designs is explained in detail below.

For the active structure, each active region can be equivalent to a cavity of a resonant cavity. The optical field intensity I in each cavity is determined by the cavity gain and cavity loss. The larger the cavity gain, the smaller the cavity loss, and the greater the optical field intensity in the corresponding resonant cavity.

Cavity loss

Among them, R1 and R2 are the reflectances of the front and rear reflection surfaces of the resonator cavity respectively. Specifically, R1 represents the reflectance of the reflective surface in the direction of the light-emitting surface, and R2 represents the reflectance of the non-light-emitting surface direction.

The smaller the cavity loss is, the longer the corresponding light in the resonator has a longer Lifetime, that is, the more times the light travels back and forth in the cavity due to reflections before exiting the resonator, and the more times it passes through the active area. The energy increment per unit length of light in the active region is proportional to I·g, where I is the intensity of the light field in the resonator. The greater the loss, the smaller the intensity of the light field; g is the gain of the active region. The larger the g, the greater the energy added by the light passing through the active area.

Fig. 7 shows the distribution of the light field intensity in the resonator cavity in the embodiment shown in Fig. 6 without a reflective layer. Among them, the abscissa in the figure represents the distance between the position of the light field and the light-emitting surface of the resonator, and the ordinate is the normalized light field intensity I. Wherein, the abscissa only intercepts the area near the active structure.

As shown in Figure 7, if no reflective layer is provided, the first and second mirrors are used as the reflection surfaces of the resonator in different active regions, and the values of R1·R2 corresponding to different active regions are Therefore, the cavity loss of the equivalent resonant cavity in each active region is similar; therefore, the light field intensity distribution in different active regions is approximately uniform.

FIG. 8 shows the distribution of the light field intensity in the resonator cavity in the embodiment shown in FIG. 6 , that is, the distribution of the light field intensity in the resonator cavity after the reflective layer is provided. Among them, the abscissa in the figure represents the distance between the position of the optical field and the light-emitting surface of the resonant cavity (that is, the distance between the surface of the resonant cavity far from the substrate 200 in FIG. 6 and the position of the optical field), and the ordinate is Normalized light field intensity I. Wherein, the abscissa only intercepts the area near the active structure.

It should be noted that, in the embodiment shown in FIG. 6 , the first mirror 210 close to the substrate 200 is an N-type doped distributed Bragg mirror, and the second mirror 240 far from the substrate 200 It is a P-type doped distributed Bragg mirror. In addition, the light exits in the direction from the first reflecting mirror 210 to the second reflecting mirror 240, so the light exits from the direction of the second reflecting mirror 240, that is, the resonant cavity is a resonant cavity that emits light from the front, so , the reflectivity of the first reflector 210 is greater than the reflectivity of the second reflector 240 .

6 and 8, the reflective layer 280 is located between the first active region 221 and the second active region 222a, the reflective layer 280 is connected to the first mirror 210, the The second mirrors 240 respectively constitute resonant cavities.

For the first active region 221, the first mirror 210 is one reflection surface of an equivalent resonant cavity, and the reflection layer 280 and the second mirror 240 are the other of the equivalent resonant cavity Reflective surface. In the first active region 221 , the coherence of the light reflected by the reflective layer and the light reflected by the second reflecting mirror 240 is enhanced. Therefore, for the first active region 221, the total reflectivity of the back to the laser exit direction (that is, the direction in which the second reflector 240 points to the first reflector 210) increases, and along the laser exit direction ( That is, the reflectivity of the first reflecting mirror 210 toward the second reflecting mirror 240 remains unchanged, that is, the setting of the reflecting layer 280 can significantly increase the value of R1 corresponding to the equivalent resonant cavity, while the value of R2 remains basically unchanged, so the value of R1·R2 in the first active region 221 can be significantly increased, so that the cavity loss of the resonant cavity equivalent to the first active region 221 can be significantly suppressed, so as shown in the figure As described in the middle circle 390, the intensity of the light field in the first active region 221 is significantly increased.

On the other hand, since the distance between the reflection layer 280 and the first reflection mirror 210 and the distance between the reflection layer 280 and the second reflection mirror 240 are different, light is reflected by the first reflection The phase difference reflected by the mirror 210 and the reflective layer 280 is different from the phase difference of the light reflected by the second mirror 240 and the reflective layer 280, so the reflective layer cannot make the light in the active area on both sides at the same time. Both achieve coherence enhancement. Therefore, when the coherence of the light in the first active region 221 is enhanced, the light in the second active regions 222 and 223 cannot be coherently enhanced, and for the second active regions 222a and 222b, all the The second reflecting mirror 240 is a reflecting surface of the equivalent resonant cavity, the reflecting layer 280 and the first reflecting mirror 210 are another reflecting surface of the equivalent resonating cavity, wherein the first reflecting mirror 210 The reflectivity is relatively high, so the setting of the reflective layer 280 has little influence on the reflectivity R2 value of the reflective surface of the equivalent resonant cavity, and has little effect on the value of the resonant cavity equivalent to the second active regions 222a and 222b. The effect of cavity loss is small, so as shown in FIG. 8 , the intensity of the light field in the second active regions 222a and 222b does not change much.

It can be seen that when the active structure is divided into two parts located on both sides of the reflective layer on a straight line along the light propagation direction, the provision of the reflective layer 280 can reduce the part of the active structure on the side away from the light emitting surface. The loss of the equivalent resonant cavity cavity is increased, thereby increasing the optical field intensity of this part, and then compensating for the gain difference caused by the quantum wells of different junction designs.

In some embodiments of the present invention, the refractive index of the material of the reflective layer 280 is different from the refractive index of the material of the first active region 221 , and the refractive index of the material of the reflective layer 280 is different from the refractive index of the material of the second active region The refractive indices of the materials 222a and 222b are different, so the reflective layer 280 can form a distributed Bragg mirror structure with adjacent material layers.

In some embodiments of the present invention, the reflective layer 280 is a distributed Bragg mirror, that is, the reflective layer 280 may be one or more periodic Bragg mirrors. Since the first reflector 210 and the second reflector 240 are generally Bragg reflectors, the reflector layer 280 is set to be the same Bragg reflector without introducing additional structures, thereby reducing the impact of introducing reflector layers on the complexity of the structure .

Specifically, in this embodiment, the reflective layer 280 is a laminated structure, and the reflective layer 280 includes a first reflective sub-layer (not shown in the figure) and a second reflective sub-layer (not shown in the figure). The refractive index of the first reflective sub-layer is not equal to the refractive index of the second reflective sub-layer. By adding the first reflection sublayer and the second reflection sublayer with high refractive index or low refractive index, an interface with a certain reflectivity is formed in the reflection layer 280, and by adjusting the thickness of the first reflection sublayer and the second reflection The thickness of the sub-layer is used to adjust the phase difference of the reflected light before and after, so as to adjust the overall reflectivity of the reflective layer 280 .

In some embodiments of the present invention, the reflection layer includes a plurality of first reflection sublayers and a plurality of first reflection sublayers, and the first reflection sublayers and the second reflection sublayers are alternately arranged, that is, the multiple reflection sublayers are arranged alternately. The first reflective sub-layers and the plurality of first reflective sub-layers are alternately arranged to adjust the overall reflectivity of the reflective layers.

One of the first reflective sub-layers and one of the second reflective sub-layers form a period, and the optical path of the light emitted from the corresponding active region of each material layer in a period is λ/4, that is, the first When the reflective sub-layer and the second reflective sub-layer both generate an optical path of λ/4, a relatively large reflectivity can be obtained; when the optical path generated by different material layers deviates from λ/4 in one cycle, that is, the first When a reflective sub-layer and the second reflective sub-layer do not generate an optical path of λ/4 at the same time, a relatively small reflectivity can be obtained. In addition, the overall reflectivity of the reflective layer can be adjusted by increasing or decreasing the number of periods, or changing the materials of the two sublayers to change the refractive index difference between the sublayers.

The overall reflectivity of the reflective layer 280 can be adjusted by changing the thickness ratio of the first reflective sublayer and the second reflective sublayer, or by increasing or decreasing the number of cycles (pairs).

In this embodiment, the actual required increase in the intensity of the light field is small, so the reflective layer is set as a low refractive index layer (half pair DBR) with a λ/4 optical path. The reflective layer and the adjacent material film layers form a structure similar to a distributed Bragg mirror.

As shown in Figure 8, after adding the reflective layer, the increase D1 of the light field intensity at the part of the active structure on the side far from the light-emitting surface relative to the light-field intensity at the part of the active structure on the side close to the light-emitting surface is about 0.83 units.

Referring to FIG. 9 , it shows the distribution of the light field intensity in the cavity in another embodiment of the resonant cavity of the present invention.

This embodiment is the same as the previous embodiment, which is not repeated in the present invention. The difference between this embodiment and the previous embodiment is that in this embodiment, the actual required increase in optical field intensity is compared with the previous embodiment. For example, it is smaller, so the reflectivity of the reflective layer is mainly adjusted by changing the thickness of the reflective layer. For example, by reducing the thickness of the reflective layer, the optical path of the reflective layer is less than λ/4 to reduce the reflection of the reflective layer. rate, so as to obtain a smaller increase in the light field. Therefore, in this embodiment, the reflective layer is set as a low refractive index layer with a thickness less than λ/4 optical path.

As shown in FIG. 9 , the abscissa represents the distance between the position of the light field and the light-emitting surface of the resonator, and the ordinate represents the normalized intensity I of the light field. Wherein, the abscissa only intercepts the area near the active structure. It can be seen from the figure that after adding the reflective layer, the increase D2 of the light field intensity at the part of the active structure on the side far from the light-emitting surface relative to the light field intensity at the part of the active structure on the side close to the light-emitting surface is about 0.64 units .

Referring to FIG. 10 , it shows the distribution of the light field intensity in the cavity in another embodiment of the resonant cavity of the present invention.

This embodiment is the same as the previous embodiment, which is not repeated in the present invention. The difference between this embodiment and the previous embodiment is that in this embodiment, the actual required increase in optical field intensity is compared with the previous embodiment. Therefore, the reflectivity of the reflective layer is mainly adjusted by changing the number of periods of the reflective layer (that is, the number of pairs), for example, by adding a high refractive index layer after the low refractive index layer to form a complete period (DBR pair). Therefore, in this embodiment, the reflective layer is set as a distributed Bragg mirror with only one period.

As shown in FIG. 10 , the abscissa represents the distance between the position of the optical field and the light-emitting surface of the resonator, and the ordinate represents the normalized intensity I of the optical field. Wherein, the abscissa only intercepts the area near the active structure. It can be seen from the figure that after adding the reflective layer, the increase D3 of the light field intensity at the part of the active structure on the side far from the light-emitting surface relative to the light field intensity at the part of the active structure on the side close to the light-emitting surface is about 1.30 units .

To sum up, by comparing Figures 8 to 10, it can be known that the higher the reflectivity of the reflective layer, the phase matching of the light reflected by the mirror and the reflective layer to obtain the optical field intensity at the position of the active structure of the coherent enhancement part and the phase mismatched part The greater the difference in the light field intensity at the position of the active structure. Therefore, by setting the reflective layers with different thicknesses, and adjusting the phase matching degree between the light emitted by the active structure and the light reflected by the reflective mirror and the reflective part, any difference in the intensity of the light field can be obtained.

Therefore, through the design of the reflective layer, and the reflective layer is arranged between the adjacent first active region 221 and the second active region 222a, the gain of the first active region 221 can be lower than that of the second active region 222a and 222b, the lower gain of the first active region 221 is compensated, so that both the first active region 221 and the second active regions 222a and 222b can work under suitable conditions. Generally speaking, a larger light field intensity needs to be set in the region of low gain value to reduce the threshold current of the device and suppress the heating of the active region. Therefore, through the setting and practice of the reflective layer, the working conditions of different active regions can be optimized respectively, so as to achieve the purpose of reducing the threshold current and improving the working state under high temperature conditions.

It should also be noted that the method of enhancing the light field intensity of the active structure on the side away from the light-emitting surface by the reflective layer is only an example. The intensity of the light field at the location of the source structure.

In an embodiment of the present invention, the position of the reflective layer can enhance the coherence between the light reflected by the reflective layer and the light reflected by the first reflecting mirror. Therefore, in the active structure on the side close to the light-emitting surface, The total reflectivity towards the laser exit direction increases, and the reflectivity along the laser exit direction remains unchanged, so that the cavity loss in the active structure close to the light exit surface is reduced; therefore, the setting of the reflective layer can enhance the close to the exit light. The intensity of the light field at the location of the active structure on one side of the face. Compared with the active structure on the side away from the light-emitting surface, the intensity of the light field in the active structure on the side close to the light-emitting surface is significantly enhanced.

Other ways to explain: you can change the reflective layer material to change the refractive index difference, thereby changing the reflectivity of the reflective layer; adjust the reflective layer material (a certain element component) to change the width of the gradient layer, the wider the gradient layer, the smaller the reflectivity.

To sum up, the setting of the reflective layer can suppress the loss of some active structures and enhance the gain of some active structures, so as to balance the gain difference of different junction design quantum wells; through the material of the reflective layer, The settings of position, thickness, and number of layers are used to adjust the gain difference of different positions in the active structure to achieve a balanced position. Correspondingly, the present invention also provides a laser unit, which specifically includes: a resonant cavity, where the resonant cavity is the resonant cavity provided by the present invention; a first electrode; and a second electrode.

Referring to FIG. 6 , a schematic cross-sectional structure diagram of an embodiment of a laser unit of the present invention is shown.

The laser unit includes: a resonant cavity, which is the resonant cavity of the present invention; a first electrode 261 ; and a second electrode 262 .

It should be noted that, in this embodiment, the laser unit is a laser unit of a vertical cavity surface emitting laser.

The technical solutions of the embodiments of the laser unit of the present invention will be described in detail below with reference to the accompanying drawings.

The resonant cavity (not marked in the figure) is the resonant cavity of the present invention. Specifically, for the specific technical solution of the resonant cavity, reference is made to the foregoing embodiments of the resonant cavity, and details are not described herein again in the present invention.

The first electrode and the second electrode realize the connection between the resonant cavity and an external circuit.

In this embodiment, the first electrode 261 is located on the side of the first mirror 210 away from the active structure, the first electrode 261 is located on the surface of the substrate 200 , and the first electrode 261 is electrically connected to the active structure through the substrate 200 and the first mirror 210; the second electrode 262 is located on the surface of the second mirror 240 on the side away from the active structure , the second electrode 262 is electrically connected to the active structure through the second mirror 240 .

In this embodiment, the direction in which the first reflecting mirror 210 points to the second reflecting mirror 240 is the same as the laser exit direction, so the second electrode 262 includes a window (not marked in the figure), and along the laser propagation direction, the window is through the second electrode 262 . The window is used to realize the exit of the laser light.

In this embodiment, the direction in which the first reflecting mirror 210 points to the second reflecting mirror 240 is the same as the laser exit direction, and the first reflecting mirror 210 and the second reflecting mirror 240 are located on the substrate 200 in sequence, Therefore, the laser unit is a front emitting laser unit.

In other embodiments of the present invention, the laser unit may also be a backside emitting laser unit.

Referring to FIG. 11 , a schematic cross-sectional structure diagram of another embodiment of the laser unit of the present invention is shown.

The laser unit includes: a resonant cavity.

The resonant cavity is the resonant cavity of the present invention, and specifically includes a first mirror 310, an active structure, and a second mirror 340 sequentially located on the substrate 300; One first active region 321 and two second active regions 322a, 322b on a reflector 310; a first active region 321 and the second active region 322a are arranged in sequence between the first active region 321 and the second active region 322a The current confinement layer 331, the first void-filling layer 371 and the first tunneling layer 351; the second current confinement layer 332 and the second void-filling layer are arranged between the second active region 322a and the second active region 322b in sequence layer 372 and the second tunneling layer 352 ; a third current confinement layer 333 is disposed between the second active region 322 b and the second mirror 340 .

Specifically, for the specific technical solution of the resonant cavity, reference is made to the foregoing embodiments of the resonant cavity, and details are not described herein again in the present invention.

This embodiment is the same as the previous embodiment, and the present invention will not repeat it again; the difference between this embodiment and the previous embodiment is that in this embodiment, the laser unit is a backside emitting laser unit, that is, the laser The laser light generated by the unit is emitted from the side of the substrate 300 , and the laser light exit direction is the same as the direction in which the second reflecting mirror 340 points to the first reflecting mirror 310 .

Therefore, the first electrode 361 is located on the side of the first mirror 310 away from the active structure, the first electrode 361 is located on the surface of the substrate 300 ; the second electrode 362 is located on the first The surface of the two mirrors 340 on the side away from the active structure. Wherein, the first electrode 361 on the surface of the substrate 300 has a window penetrating along the direction of the laser light, so as to realize the output of the laser light.

In this embodiment, a first active region 321 with tensile strain is first formed on the substrate 300 , and second active regions 322 a and 322 b with compressive strain are formed on the first active region 321 , so that the compressive strain generated by the formation of the first mirror 310 and the first current confinement layer can be balanced, thereby achieving the purpose of improving the quality of the second active regions 322a and 322b.

The fact that the reflective layer is not provided in the backside emitting laser unit is only an example, and in other embodiments of the present invention, the reflective layer may also be provided in the backside emitting laser unit.

Referring to FIG. 12 , a schematic cross-sectional structure diagram of another embodiment of the laser unit of the present invention is shown.

The laser unit includes: a resonant cavity.

The resonant cavity is the resonant cavity of the present invention, and specifically includes a first reflector 410, an active structure, and a second reflector 440 sequentially located on the substrate 400; wherein the active structure includes sequentially located on the first mirror 410. One first active region 421 and two second active regions 422a, 422b on a mirror 410; a first active region 421 and the second active region 422a are arranged in sequence between the first active region 421 and the second active region 422a the current confinement layer 431 , the first void filling layer 471 and the first tunneling layer 451 ; the second current confinement layer 432 and the second void filling layer are arranged between the second active region 422 a and the second active region 422 b in sequence layer 472 and the second tunneling layer 452 ; a third current confinement layer 433 is disposed between the second active region 422 b and the second mirror 440 .

Specifically, for the specific technical solution of the resonant cavity, reference is made to the foregoing embodiments of the resonant cavity, and details are not described herein again in the present invention.

In this embodiment, the laser unit is a backside emitting laser unit, that is, the laser light generated by the laser unit is emitted from the side of the substrate 400 , and the laser exit direction and the second reflecting mirror 440 are directed to the second mirror 440 . The direction of a mirror 410 is the same.

The present embodiment is the same as the previous embodiment, which is not repeated in the present invention; the difference between this embodiment and the previous embodiment is that in this embodiment, in the first active region 421, the material of the barrier region is The tensile stress is very large, so that the gain of the first active region 421 is greater than the gain of the second active regions 422a and 422b. Therefore, in the active structure, the first active region 421 and the second active region The reflective layer 480 is disposed between the two active regions 422a, so that the light of the second active regions 422a and 422b can achieve coherence enhancement after being reflected by the first mirror 410, the second mirror 440 and the reflective layer 480, while the The light of an active region 421 cannot be coherently enhanced, so as to reduce the light field intensity at the position of the first active region 421, thereby achieving a balance of energy gains of different active regions in the active structure.

As shown in FIG. 12, in some embodiments of the present invention, in a plane perpendicular to the laser propagation direction, the laser unit includes a core region 401 and an extension region 402; the resonant cavity is located in the core region 401; and the The first reflection mirror 410 extends to the extension area 402 ; the first electrode 461 is in contact with the first reflection mirror 410 of the extension area 402 . The first electrode 461 is electrically connected to the active structure through the first mirror 410 .

Specifically, in this embodiment, the first electrode 461 is located on the surface of the first reflecting mirror 410 of the extending region 402 facing the second reflecting mirror 440 . By arranging the first electrode 461 on the surface of the first reflection mirror 410 of the extension region 402 facing the second reflection mirror 440, the first electrode 461 and the second electrode 462 can face the same side, thereby It can provide a good foundation for the fabrication of the subsequent coplanar electrodes, which is beneficial to reduce the packaging difficulty of the laser unit and improve the packaging quality.

In addition, the present invention also provides a laser, which specifically includes: a laser unit, where the laser unit is the laser unit of the present invention.

Since the laser unit is the laser unit of the present invention, the specific technical solutions of the laser unit refer to the embodiments of the laser unit described above, and the present invention will not repeat them here.

It should be noted that, in this embodiment, the laser is a vertical cavity surface emitting laser.

In the laser, in the laser unit, the active structure of the resonator includes a first active region and a second active region, wherein the material of the first active region has tensile strain, and the material of the second active region Has compressive strain. The first active region with tensile strain can release the compressive stress introduced by the second active region, preventing stress accumulation and avoiding stress release; therefore, the arrangement of the first active region and the second active region can While ensuring the gain of the active structure, achieving stress balance and suppressing the generation of structural defects is conducive to improving the quality of the resonator cavity, improving the external quantum efficiency and power, and improving the reliability of the device.

In addition, the present invention also provides a laser radar, which specifically includes: a light source, and the light source includes the laser of the present invention.

Since the resonant cavity of the laser of the present invention can achieve stress balance while ensuring the gain of the active structure, and suppress the generation of structural defects, the resonant cavity has high quality, high external quantum efficiency and power, and high reliability; therefore, the present invention is adopted. As the light source of the lidar, the laser can effectively improve the quality, power and reliability of the light source, effectively expand the detection distance of the lidar, ensure the detection accuracy of the lidar, and improve the reliability of the lidar.

To sum up, in the resonator cavity of the present invention, the active structure includes a first active region and a second active region, wherein the material of the first active region has tensile strain, and the material of the second active region has compressive strain. The second active region with compressive stress has higher gain and can adjust the band gap to adjust the working band, and the first active region with tensile strain can release the compressive stress introduced by the second active region and prevent stress accumulation, Avoid stress release; therefore, the arrangement of the first active region and the second active region can achieve stress balance while ensuring the gain of the active structure, suppress the generation of structural defects, and help improve the quality of the resonant cavity. It is beneficial to improve the external quantum efficiency and power, and is beneficial to improve the reliability of the device.

Although the present invention is disclosed above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be based on the scope defined by the claims.

Claims (27)

1. A resonant cavity, characterized in that, comprising:

   a first reflector and a second reflector, the first reflector and the second reflector are relatively spaced apart;

   an active structure, the active structure is located between the first mirror and the second mirror; the active structure includes one or more first active regions and one or more second active regions region, the material of the first active region has tensile strain, and the material of the second active region has compressive strain.
2. The resonant cavity of claim 1, wherein at least one of the first active region and the second active region is a quantum well active region, and the quantum well active region comprises a potential barrier region and a potential well region between adjacent barrier regions.
3. The resonant cavity of claim 2, wherein the first active region comprises:

   An overcompensated quantum well, the second active region includes: a compressively strained quantum well.
4. The resonant cavity according to claim 3, wherein the material of the potential well region of the first active region has compressive strain, and the material of the potential barrier region of the first active region has tensile strain;

   The stress magnitude of the tensile strain of the material of the barrier region of the first active region is greater than the magnitude of the stress of the compressive strain of the material of the potential well region of the first active region.
5. The resonator cavity according to any one of claims 2 to 4, wherein the material of the potential well region of the first active region is InGaAs, and the material of the barrier region of the first active region is GaAsP, At least one of AlGaAsP.
6. The resonant cavity according to claim 3, wherein the material of the potential well region of the second active region has compressive strain, and the material of the potential barrier region of the second active region has compressive strain,

   The stress magnitude of the compressive strain of the barrier region material of the second active region is smaller than the stress magnitude of the compressive strain of the potential well region material of the second active region.
7. The resonant cavity according to claim 2 or 6, wherein the material of the potential well region of the second active region is InGaAs, and the material of the potential barrier region of the second active region is AlGaAs.
8. The resonant cavity according to claim 3, wherein the material of the potential well region of the second active region has compressive strain, and the material of the potential barrier region of the second active region has no strain.
9. 3. The resonant cavity of claim 2, wherein the quantum well active region comprises a plurality of quantum wells.
10. The resonant cavity of claim 1, wherein the material of the first mirror comprises N-type dopant ions;

    One of the first active regions is located on the surface of the first mirror.
11. The resonant cavity of claim 1, further comprising: a reflection layer, the reflection layer is located between the adjacent first active regions and the second active regions.
12. The resonant cavity of claim 11, wherein the first active region is located on one side of the reflective layer, and the one or more second active regions are located on the other side of the reflective layer .
13. The resonant cavity according to claim 11, wherein the refractive index of the material of the reflective layer is different from the refractive index of the material of the first active region, and the refractive index of the material of the reflective layer is different from the refractive index of the material of the first active region. The refractive indices of the two active region materials are different.
14. The resonant cavity of claim 11, wherein the reflection layer is a distributed Bragg mirror.
15. The resonant cavity according to claim 11 or 14, wherein the reflection layer is a laminated structure, the reflection layer comprises a first reflection sublayer and a second reflection sublayer, and the first reflection sublayer has a The refractive index is not equal to the refractive index of the second reflective sublayer.
16. The resonant cavity according to claim 15, wherein the first reflection sub-layers and the second reflection sub-layers are alternately arranged.
17. The resonant cavity of claim 1, wherein the active region has a first surface and a second surface opposite to each other, and the direction of the first surface pointing to the second surface is consistent with the current direction;

    The resonant cavity further includes a current confinement layer on at least the first surface.
18. The resonant cavity of claim 17, wherein the current confinement layer is provided on the surface of the first active region facing the second active region.
19. The resonant cavity of claim 1, further comprising: a substrate, the substrate is located on a side of the first mirror away from the active structure.
20. The resonant cavity according to claim 19, wherein the substrate is an N-type substrate, the dopant ions contained in the first reflector are N-type ions, and the dopant ions contained in the second reflector The ions are P-type ions.
21. A laser unit, characterized in that it includes:

    a resonant cavity, the resonant cavity is the resonant cavity according to any one of claims 1 to 20;

    the first electrode;

    second electrode.
22. The laser unit of claim 21, wherein the second electrode is located on a surface of the second mirror on a side away from the active structure.
23. The laser unit of claim 21, wherein the first electrode is located on a side of the first mirror away from the active structure, and the first electrode is located on a surface of the substrate.
24. 24. The laser unit of claim 23, wherein the second electrode comprises a window, and the window penetrates the second electrode along the laser light propagation direction.
25. A laser, characterized by comprising: a laser unit, wherein the laser unit is the laser unit according to any one of claims 21-24.
26. The laser of claim 25, wherein the laser is a vertical cavity surface emitting laser.
27. A lidar, characterized by comprising:

    A light source comprising the laser of any one of claims 25-26.

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