Single-mode narrow-linewidth high-power three-section type semiconductor laser and preparation and working method thereof

Abstract

The single-mode narrow-linewidth high-power three-section type semiconductor laser comprises a first light field adjusting area, a second light field adjusting area and a phase shift adjusting area which are arranged in sequence, the first light field adjusting area is close to the light emitting end face of the laser, and the first light field adjusting area, the second light field adjusting area and the phase shift adjusting area are each provided with an independent electrode; the first light field adjusting area, the second light field adjusting area and the phase shift adjusting area share the same grating layer and the same waveguide structure; the light-emitting end face is plated with an anti-reflection film, and the other end face is plated with a high-reflection film. The semiconductor laser provided by the invention can be compatible with high power, narrow linewidth and good single-mode characteristics, and has flexible and accurate regulation and control capability.

Description

Technical Field

[0001] The invention belongs to the field of optoelectronic technology, and in particular relates to a single-mode narrow-linewidth high-power three-segment semiconductor laser and a preparation and working method thereof. Background Art

[0002] Single-mode narrow linewidth high-power DFB semiconductor lasers are widely used in laser radar, fiber optic sensing, fiber optic communication, precision measurement and other fields. Taking laser radar as an example, the narrow linewidth characteristics of laser as a light source significantly improve the detection resolution of the system. This high resolution can effectively distinguish between similar objects and improve the accuracy and clarity of target recognition. In addition, the high-power output of the laser further extends the detection distance, making long-distance measurement in complex environments possible. Therefore, the combination of single-mode narrow linewidth high-power semiconductor lasers not only optimizes the performance of the laser radar system, but also provides reliable guarantees for high-precision measurement and data acquisition, and promotes the advancement of related technologies and the expansion of applications.

[0003] There has been a lot of progress in the research of single-mode narrow linewidth high-power DFB semiconductor lasers. Common high-power implementation methods include tapered waveguides, slab-coupled waveguides, etc., and narrow linewidth implementation methods include external cavity feedback, injection locking, etc. However, these methods have limitations such as difficulty in on-chip integration and complex process requirements. In the prior art, in order to increase the laser power and narrow the linewidth, a relatively simple method is to use a coating structure of high-reflection film and anti-reflection film. However, in the process of increasing the injection current to increase the laser power, this coating structure will cause a large number of photons to accumulate at one end of the high-reflection film, resulting in uneven distribution of the intracavity light field, and then produce spatial hole burning effect Intensification and carrier density fluctuations, which seriously affect the single-mode characteristics and narrow linewidth output of the laser, thereby limiting the maximum output power of the laser; in addition, since the end face of the high-reflection film will produce a random phase for the grating feedback during the cleavage process, the laser will cause the overall phase to change during continuous power-on operation, resulting in a low difference in the gain threshold between the main mode and the side mode as the refractive index changes, and an uncontrollable mode hopping problem will occur. Especially in application scenarios that have extremely high requirements on the quality of light source signals, this phenomenon will directly reduce system performance and even make it impossible to guarantee the normal operation of the system.

[0004] The invention with publication number CN108155557B discloses a semiconductor laser and a control method, including grating regions and phase shift structures; the grating regions are made in series on the same laser chip; the grating period in each grating region remains unchanged, and the grating period of different grating regions increases or decreases along the laser chip; any two adjacent grating regions inject current to generate single-mode laser emission; there is a phase shift structure between adjacent grating regions, and the phase shift value is in the range of 0° to 360°. This invention can solve the problem of tunable multi-wavelength lasers being too long and having unreliable quality. However, this invention does not involve the technical problem of insufficient compatibility between high power and narrow linewidth.

[0005] The invention with the publication number CN111934201A discloses a tunable laser silicon-based hybrid integration and a tunable laser and a preparation method thereof. The tunable surface-emitting horizontal cavity laser includes an epitaxial structure body, and the upper end of the epitaxial structure body is provided with multiple ridge waveguides of different lengths at intervals along the waveguide transmission direction to achieve the superposition of comb spectra with different spacings. The upper end of the epitaxial structure body is provided with an N electrode and multiple P electrodes. The horizontal cavity ridge waveguide of the epitaxial structure body is provided with a surface-emitting vertical coupling grating for realizing the vertical coupling surface emission of the horizontal resonant cavity laser. The tunable surface-emitting laser is flip-chip mounted on a silicon-based substrate, and multiple pads are provided on the silicon-based substrate. The upper ends of the multiple pads are used to be welded with the N electrode and multiple P electrodes of the tunable surface-emitting laser one by one, respectively, and the surface emission and silicon-based hybrid integration are achieved through the vertical coupling of the detuned multi-order grating. However, the invention uses multiple ridge waveguides to form multiple FP cavities, which makes it difficult to solve the problem of accurate optimization of light field distribution and line width power.

[0006] In summary, existing DFB semiconductor lasers face the following problems in applications: the spatial hole burning effect and carrier fluctuations caused by the uneven distribution of the light field in the cavity limit the stability of the narrow line width output; the multi-mode mode hopping phenomenon caused by the random phase brought by the high-reflection film seriously affects the single-mode characteristics of the laser; the compatibility between high power and narrow line width is insufficient, making it difficult to meet the needs of high-performance light source scenarios; in addition, the control accuracy and flexibility are limited, and it is impossible to achieve accurate optimization of the light field distribution and line width power. These problems significantly limit the development potential of DFB semiconductor lasers in high-performance applications. Summary of the invention

[0007] In view of the deficiencies in the prior art, the present invention provides a single-mode narrow-linewidth high-power three-segment semiconductor laser and its preparation and working method. The semiconductor laser of the present invention can be compatible with high power, narrow linewidth and good single-mode characteristics, and at the same time has flexible and precise control capabilities.

[0008] Technical solution:

[0009] In a first aspect, the present invention discloses a single-mode narrow-linewidth high-power three-section semiconductor laser, the semiconductor laser comprising a first light field adjustment area (101), a second light field adjustment area (102) and a phase shift adjustment area (103) arranged in sequence, and the first light field adjustment area (101) is adjacent to the light-emitting end face of the laser, and the first light field adjustment area (101), the second light field adjustment area (102) and the phase shift adjustment area (103) are all provided with independent electrodes (104); the first light field adjustment area (101), the second light field adjustment area (102) and the phase shift adjustment area (103) share the same grating layer (20) and the same waveguide structure; the light-emitting end face of the laser end is plated with an anti-reflection film (105), and the other end face is plated with a high-reflection film (106);

[0010] The laser controls the light field distribution in the cavity by injecting differential currents into the first light field adjustment area (101) and the second light field adjustment area (102); and fine-tunes the injection current of the phase shift adjustment area (103) so that the laser continues single longitudinal mode lasing while maintaining line width and power.

[0011] Furthermore, the proportion of the first light field adjustment area (101) occupied by the overall cavity length is greater than the proportion of the second light field adjustment area (102) occupied by the overall cavity length; and the number of photons that can be regulated by the electrodes in the first light field adjustment area (101) and the second light field adjustment area (102) tend to be consistent.

[0012] Furthermore, the overall cavity length of the laser is greater than or equal to 1500 microns, the first light field adjustment zone (101) and the second light field adjustment zone (102) together occupy a proportion greater than or equal to 95% of the overall cavity length, and the phase shift adjustment zone (103) occupies a proportion less than or equal to 5% of the overall cavity length.

[0013] Furthermore, the grating layer (20) is prepared as a sampled grating structure in the first light field adjustment area (101) and the second light field adjustment area (102), and is prepared as a non-grating structure in the phase shift adjustment area (103).

[0014] Furthermore, the laser is a ridge waveguide structure or a buried heterojunction waveguide structure.

[0015] Furthermore, the width of the laser ridge waveguide is greater than or equal to 2.6 microns.

[0016] In a second aspect, the present invention discloses a method for preparing a single-mode narrow-linewidth high-power three-segment semiconductor laser, the preparation method comprising the following steps:

[0017] S1, performing the first epitaxial material growth, wherein the material grows from the substrate through the buffer layer, the lower confinement layer, the active layer, the upper confinement layer to the grating layer (20);

[0018] S2, using a reconstruction equivalent chirp technique to perform sampling grating production on the grating layer (20);

[0019] S3, performing a second epitaxial material growth, and sequentially growing a grating buried layer, a waveguide corrosion barrier layer, a waveguide layer and a contact layer on the grating layer (20);

[0020] S4, corroding the waveguide layer and the contact layer to form a ridge shape, and obtaining mutually isolated first light field adjustment area (101), second light field adjustment area (102) and phase shift adjustment area (103) through electrical isolation and opening electrode windows, and performing positive electrode evaporation on the contact layer to form independent electrodes (104) of the first light field adjustment area (101), the second light field adjustment area (102) and the phase shift adjustment area (103);

[0021] S5. Thin and polish the back side of the substrate, evaporate the back side electrode and heat it to obtain an alloy, cleave the chip into bars, and perform end-face coating to obtain a three-segment semiconductor laser.

[0022] In a third aspect, the present invention discloses a working method of a single-mode narrow-linewidth high-power three-segment semiconductor laser, the working method comprising the following steps:

[0023] S1. Based on the semiconductor laser linewidth theory, narrow linewidth and high-power laser output is initially achieved by extending the cavity length and increasing the ridge width;

[0024] S2, controlling the working current injection ratio of the first light field adjustment area (101) and the second light field adjustment area (102) according to the light field distribution characteristics to adjust the light field distribution in the cavity and make the light field distribution flat;

[0025] S3, adjusting the injection current of the laser light field adjustment area to seek the optimal state of line width and power;

[0026] S4. If the laser is multi-mode during the power-on process, the phase is adjusted by fine-tuning the injected current in the phase shift adjustment zone to keep the laser lasing in single longitudinal mode while maintaining the line width and power.

[0027] Beneficial effects:

[0028] First, the single-mode, narrow-linewidth, high-power three-segment semiconductor laser of the present invention and its preparation and working method increase the power by extending the cavity length and increasing the ridge width, while narrowing the linewidth of the laser, and are suitable for application scenarios such as laser radar that have high requirements on light sources.

[0029] Second, the single-mode narrow-linewidth high-power three-segment semiconductor laser of the present invention and its preparation and working method, by differentially injecting current into the first two light field adjustment zones to regulate the light field distribution in the cavity, promotes the flattening of the light field distribution, effectively reduces the spatial hole burning effect and carrier fluctuations, and can further obtain the optimal power and linewidth state of the laser.

[0030] Third, the single-mode narrow-linewidth high-power three-segment semiconductor laser of the present invention and its preparation and working method, the phase shift adjustment zone solves the uncontrollable mode hopping problem caused by the phase of the high-reflection film end face and the change of the refractive index during the current injection process by fine-tuning the phase shift current, thereby ensuring the single-mode output of the laser while maintaining the regulated light field distribution unchanged.

[0031] Fourth, the single-mode narrow-linewidth high-power three-segment semiconductor laser of the present invention and its preparation and working method realize the function of accurately adjusting each segment through independent power supply of three segments, which effectively enhances the flexibility and stability of laser control. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A schematic diagram of the structure of a single-mode narrow-linewidth high-power three-segment semiconductor laser provided by the present invention;

[0033] Figure 2 A schematic diagram of the grating layer of a single-mode, narrow-linewidth, high-power three-segment semiconductor laser provided by the present invention;

[0034] Figure 3 Schematic diagram of the intracavity light field distribution of the semiconductor laser in Example 1;

[0035] Figure 4 Schematic diagram of the spectrum characteristic curve of the single-mode narrow-linewidth high-power three-segment semiconductor laser under uniform power-on in Example 3;

[0036] Figure 5 The intracavity light field distribution diagram of the single-mode narrow-linewidth high-power three-segment semiconductor laser in Example 3 under different power-on ratios;

[0037] Figure 6 The diagram is a diagram of the intracavity optical field flatness and the total optical field intensity of the single-mode narrow-linewidth high-power three-segment semiconductor laser in Example 3 at different power-on ratios;

[0038] Figure 7 Schematic diagram of the correction process of the single-mode narrow-linewidth high-power three-segment semiconductor laser after multi-mode occurs in Example 3;

[0039] Figure 8 It is a schematic diagram of the special grating design result for the light field adjustment area in Example 4;

[0040] Fig. 9Schematic diagram of the simulation comparison results of the final intracavity light field in Example 4 and the original light field. DETAILED DESCRIPTION

[0041] The following examples will enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0042] Example 1

[0043] The present invention discloses a single-mode narrow-linewidth high-power three-section semiconductor laser. The semiconductor laser comprises a first light field adjustment area 101, a second light field adjustment area 102 and a phase shift adjustment area 103 which are arranged in sequence, and the first light field adjustment area 101 is adjacent to the light-emitting end face of the laser. The first light field adjustment area 101, the second light field adjustment area 102 and the phase shift adjustment area 103 are all provided with independent electrodes 104. The first light field adjustment area 101, the second light field adjustment area 102 and the phase shift adjustment area 103 share the same grating layer 20 and the same waveguide structure. The light-emitting end face of the laser end is plated with an anti-reflection film 105, and the other end face is plated with a high-reflection film 106.

[0044] See attached Figures 1 to 3 The embodiment of the present invention provides a single-mode narrow-linewidth high-power three-section semiconductor laser, which realizes three partitions by electrically isolating the ridge waveguide, namely two light field adjustment areas (a first light field adjustment area 101 and a second light field area 102) and a phase shift adjustment area 103, and the three partitions have independent power supply electrodes; in the ridge waveguide structure, in order to ensure the high-power effect, the ridge waveguide width is 2.8 microns in this embodiment; the laser is stacked from bottom to top by a substrate, a buffer layer, a lower confinement layer, a multi-quantum well layer, an upper confinement layer, a grating layer, a corrosion barrier layer, a waveguide layer and a contact layer; wherein the multi-quantum well layer adopts a three-quantum well structure; the light-inlet end face of the waveguide structure is coated with a high-reflection film, and the light-outlet end face is coated with an anti-reflection film.

[0045] In order to ensure the initial laser output with narrow line width and high power, the overall cavity length of the laser is set to be greater than or equal to 1500 microns, and the laser ridge waveguide width is greater than or equal to 2.6 microns. In the division of the three regions, the sum of the first section of the light field adjustment area and the second section of the light field adjustment area occupies a proportion greater than or equal to 95% of the overall cavity length, and the phase shift adjustment area occupies a proportion less than or equal to 5% of the overall cavity length. Figure 1As shown, in the three sections of the single-mode narrow linewidth high-power three-section semiconductor laser, the first light field adjustment area 101 and the second light field adjustment area 102 are close to the anti-reflection film 105, and the phase shift adjustment area 103 is close to the high-reflection film 106. In this embodiment, the laser cavity length is 2000 microns, and the lengths of the first light field adjustment area 101, the second light field adjustment area 102 and the phase shift adjustment area 103 are 1333 microns, 566 microns and 100 microns respectively; the laser ridge waveguide width is 3.2 microns.

[0046] In this embodiment, the three regions share a grating layer, which is prepared by reconstructing equivalent chirp technology. The two sections of the light field adjustment area are uniformly sampled grating structures, and the output of the required wavelength is achieved by using ±1-order diffraction. At the same time, in order to ensure that the phase shift adjustment area only acts on the phase shift and has no additional impact on the transmission reflection spectrum, light field, etc., the length of the phase shift adjustment area is set to be shorter, and its grating layer does not have a grating structure. According to the coating method of the laser using high reflection film and anti-reflection film, its common light field distribution characteristics are as follows: Figure 3 As shown, a large number of photons are concentrated near the high-reflection film end, while a relatively small number of photons are distributed near the anti-reflection film end. Therefore, the first light field adjustment area has a larger range and is close to the anti-reflection film, while the second light field adjustment area has a smaller range and is close to the high-reflection film. The purpose is to ensure that the number of photons that can be regulated by the electrodes in the two areas is basically the same, and to be able to adjust the light field distribution more accurately.

[0047] Example 2

[0048] On the basis of the above embodiments, the present invention discloses a method for preparing a single-mode narrow-linewidth high-power three-segment semiconductor laser, comprising the following steps:

[0049] S1. A buffer layer and a lower confinement layer are sequentially deposited on a substrate by metal organic compound vapor phase, and then a multi-quantum well layer is grown on the lower confinement layer, an upper confinement layer is grown on the multi-quantum well layer, and then a grating layer is grown on the upper confinement layer.

[0050] S2, the grating layer is a laser grating, and the uniformly sampled grating is produced by using the reconstruction equivalent chirp technology.

[0051] S3. InP is deposited above the grating layer to bury the grating layer, and then a corrosion barrier layer, a waveguide layer and a contact layer are grown in sequence.

[0052] S4. The waveguide layer and the contact layer are corroded to form a ridge shape, and two mutually isolated light field adjustment regions and a phase shift adjustment region are obtained by etching, and a front metal electrode is grown in the ridge region above the contact layer.

[0053] S5, thinning and polishing the back side of the substrate, evaporating the back side electrode and heating to obtain an alloy, cleaving the chip into bars, and performing end face coating to obtain the three-segment semiconductor laser.

[0054] Example 3

[0055] On the basis of the above embodiments, the present invention discloses an application method based on a single-mode narrow linewidth high-power three-segment semiconductor laser, comprising the following steps:

[0056] S1. According to the semiconductor laser line width theory, narrow line width and high power laser output are preliminarily realized by extending the cavity length and increasing the ridge width. Here, the laser described in Example 1 is used as the research object, with a cavity length of 2000 microns and a ridge waveguide width of 3.2 microns.

[0057] S2. Inject proportional current into the laser according to the length ratio of the laser partitions, and achieve initial lasing by increasing the current size. In this embodiment, the lengths of the three sections are 1333 microns, 566 microns, and 100 microns, respectively. Therefore, the ratio of the injected current is 1333:566:100. For example, when the total current of this laser is 500 mA, the current of each section is 333 mA, 142 mA, and 25 mA, respectively. Figure 4 The output spectrum of this embodiment is shown when the total current is gradually increased from 200 mA to 500 mA under proportional power application.

[0058] S3. According to the characteristics of the light field distribution in the cavity, the working current injection size of the two light field adjustment areas is controlled. A larger current is injected into the low-density light field area and a smaller current is injected into the high-density light field area to achieve a flat light field distribution and reduce the spatial hole burning effect. In this embodiment, the standard deviation and integral sum of the light field intensity at different positions in the cavity are defined as the evaluation indicators of the light field flatness and the total amount of the light field in the cavity. The total current of 500 mA is maintained unchanged, and the current density ratio in different areas is regulated by adjusting the injection current of each electrode. Figure 3 The light field distribution characteristics in the cavity shown can be optimized by increasing the current in the first light field adjustment area and reducing the current in the second light field adjustment area. The light field distribution results under several common current ratios are presented in Figure 5 , the light field flatness and the total light field intensity are summarized in Figure 6 It can be seen that the current regulation process has little effect on the total amount of light field in the laser cavity, but when the current density ratio is 1.18 / 0.64 / 0.64, the light field flatness factor is reduced by 47.46%, and the laser power is also increased by 13.58%.

[0059] S4. Because of the random phase caused by the high-reflection film used in the laser, the laser will have multi-mode and mode-hopping problems at a certain current during the power-on process. At this time, the injection current in the phase shift adjustment area can be fine-tuned to generate a stable phase to avoid this problem. In this embodiment, this process is reflected in Figure 7 As shown, mode conversion is achieved within a current regulation period of 2 mA, ensuring the single-mode output of the laser without significantly affecting the light field distribution.

[0060] Example 4

[0061] Further improvement on the basis of Example 1:

[0062] A special grating structure is designed for the two light field adjustment areas. By using REC technology to adjust the grating sampling duty cycle, the distributed control of the grating coupling coefficient is realized, and the light field is flattened, and the goal of narrow line width is finally achieved. In the process of grating design, the machine learning optimization algorithm is combined. The designed grating structure and duty cycle distribution are as follows Figure 8 As shown in Figure 2, the simulation effect of the final cavity light field is compared with the simulation of the original light field. Fig. 9 As shown, the light field flattening effect is improved by 83.45% compared with the grating structure in Example 1.

[0063] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A single-mode narrow-linewidth high-power three-segment semiconductor laser, characterized in that: The semiconductor laser comprises a first light field adjustment region (101), a second light field adjustment region (102) and a phase shift adjustment region (103) arranged in sequence, and the first light field adjustment region (101) is adjacent to the light emitting end face of the laser, and the first light field adjustment region (101), the second light field adjustment region (102) and the phase shift adjustment region (103) are all provided with independent electrodes (104); the first light field adjustment region (101), the second light field adjustment region (102) and the phase shift adjustment region (103) share the same grating layer (20) and the same waveguide structure; the light emitting end face of the laser end is plated with an anti-reflection film (105), and the other end face is plated with a high-reflection film (106); The laser controls the light field distribution in the cavity by injecting differential currents into the first light field adjustment area (101) and the second light field adjustment area (102); and fine-tunes the injection current of the phase shift adjustment area (103) so that the laser continues single longitudinal mode lasing while maintaining line width and power.

2. The single-mode narrow-linewidth high-power three-segment semiconductor laser according to claim 1, characterized in that: The proportion of the first light field adjustment area (101) occupied by the overall cavity length is greater than the proportion of the second light field adjustment area (102) occupied by the overall cavity length; the number of photons that can be regulated by the electrodes in the first light field adjustment area (101) and the second light field adjustment area (102) tends to be consistent.

3. The single-mode narrow-linewidth high-power three-segment semiconductor laser according to claim 1, characterized in that: The overall cavity length of the laser is greater than or equal to 1500 microns, the first light field adjustment area (101) and the second light field adjustment area (102) together occupy a proportion greater than or equal to 95% of the overall cavity length, and the phase shift adjustment area (103) occupies a proportion less than or equal to 5% of the overall cavity length.

4. The single-mode narrow-linewidth high-power three-segment semiconductor laser according to claim 1, characterized in that: The grating layer (20) is prepared as a sampled grating structure in the first light field adjustment area (101) and the second light field adjustment area (102), and is prepared as a non-grating structure in the phase shift adjustment area (103).

5. The single-mode narrow-linewidth high-power three-segment semiconductor laser according to claim 1, characterized in that: The laser is a ridge waveguide structure or a buried heterojunction waveguide structure.

6. The single-mode narrow-linewidth high-power three-segment semiconductor laser according to claim 1, characterized in that: The width of the laser ridge waveguide is greater than or equal to 2.6 microns.

7. A method for preparing a single-mode narrow-linewidth high-power three-segment semiconductor laser according to any one of claims 1 to 6, characterized in that: The preparation method comprises the following steps: S1, performing the first epitaxial material growth, wherein the material grows from the substrate through the buffer layer, the lower confinement layer, the active layer, the upper confinement layer to the grating layer (20); S2, using a reconstruction equivalent chirp technique to perform sampling grating production on the grating layer (20); S3, performing a second epitaxial material growth, and sequentially growing a grating buried layer, a waveguide corrosion barrier layer, a waveguide layer and a contact layer on the grating layer (20); S4, corroding the waveguide layer and the contact layer to form a ridge shape, and obtaining mutually isolated first light field adjustment area (101), second light field adjustment area (102) and phase shift adjustment area (103) through electrical isolation and opening electrode windows, and performing positive electrode evaporation on the contact layer to form independent electrodes (104) of the first light field adjustment area (101), the second light field adjustment area (102) and the phase shift adjustment area (103); S5. Thin and polish the back side of the substrate, evaporate the back side electrode and heat it to obtain an alloy, cleave the chip into bars, and perform end-face coating to obtain a three-segment semiconductor laser.

8. A method for operating a single-mode narrow-linewidth high-power three-segment semiconductor laser according to any one of claims 1 to 6, characterized in that: The working method comprises the following steps: S1. Based on the semiconductor laser linewidth theory, narrow linewidth and high-power laser output is initially achieved by extending the cavity length and increasing the ridge width; S2, controlling the working current injection ratio of the first light field adjustment area (101) and the second light field adjustment area (102) according to the light field distribution characteristics to adjust the light field distribution in the cavity and make the light field distribution flat; S3, adjusting the injection current of the laser light field adjustment area to seek the optimal state of line width and power; S4. If the laser is multi-mode during the power-on process, the phase is adjusted by fine-tuning the injected current in the phase shift adjustment zone to keep the laser lasing in single longitudinal mode while maintaining the line width and power.

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