Waveguide for improving cavity temperature distribution of high-power semiconductor laser chip and semiconductor laser chip

Abstract

The invention relates to a waveguide of a semiconductor laser chip, in particular to a waveguide for improving cavity temperature distribution of a high-power semiconductor laser chip and the semiconductor laser chip, and aims to solve the problems that when an existing high-power semiconductor laser chip works, the cavity temperature is too high; however, the traditional solution only passively relieves the high temperature of the cavity caused by large current injection, and cannot fundamentally solve the technical problem that the temperature of the cavity is too high when the high-power semiconductor laser chip works. The laser chip comprises a P limiting layer and a ridge waveguide which are arranged from bottom to top, a plurality of transverse isolation grooves are formed in the upper surface of the ridge waveguide and serve as electric insulation isolation areas, the ridge waveguide and part of the P limiting layer are divided into a plurality of window areas and a plurality of lasing areas which are alternately distributed in the cavity length direction of the laser chip, and the window areas are used for low-voltage current injection; the low voltage is slightly smaller than the threshold voltage of the laser chip, the plurality of lasing areas are used for high-voltage current injection, and the high voltage is larger than the threshold voltage of the laser chip.

Description

Technical Field

[0001] The present invention relates to a waveguide of a semiconductor laser chip, in particular to a waveguide and a semiconductor laser chip for improving the temperature distribution of a high-power semiconductor laser chip cavity. Background Art

[0002] High-power semiconductor laser chips are widely used in materials processing, fiber coupling, medical treatment, communications and other fields due to their advantages such as high output power, high conversion efficiency and high brightness. With the advancement of technologies to reduce internal losses and optimize electrical characteristics, high-power semiconductor laser chips can achieve longer cavity lengths. However, due to longitudinal spatial hole burning and nonlinear physical effects, the maximum cavity length of GaAs (gallium arsenide)-based high-power semiconductor laser chips is still limited to about 6mm. In addition, although GaAs-based high-power semiconductor laser chips have achieved an electro-optical conversion efficiency of about 70%, a large amount of electrical energy is still converted into heat, which in turn has a negative impact on the output characteristics and reliability of the laser chip.

[0003] Self-heating is the main source of heat in high-power semiconductor laser chips. The high heat of the laser chip cavity increases the junction temperature, deteriorates the laser output performance, reduces the life of the laser chip, and reduces the reliability of the laser chip. Therefore, improving the temperature distribution of the high-power semiconductor laser chip cavity and reducing the junction temperature are of great significance and application value. GaAs-based high-power edge-emitting semiconductor lasers usually adopt a ridge waveguide structure. The laser structure from bottom to top is GaAs substrate, N confinement layer, N waveguide layer, active layer, P waveguide layer, P confinement layer and ridge waveguide. High current injection is required for high-power laser output. High drive current will directly lead to an increase in light absorption heat, Joule heating and carrier non-radiative recombination in the laser chip. After photons are absorbed by the material, the cavity temperature rises, exacerbating carrier diffusion and causing them to diffuse toward the active region, resulting in a decrease in the carrier concentration in the active region. Internal Joule heat accumulation causes the semiconductor material's lattice to expand and the band gap to decrease, shifting the emission wavelength toward longer wavelengths, creating a redshift and increasing the light absorption coefficient, forming a positive feedback loop of light absorption and temperature rise. Non-radiative carrier recombination does not produce photons, but converts the injected electrical energy into heat, causing the laser chip's electro-optical conversion efficiency to decrease, affecting performance. Long-term non-radiative recombination also accelerates material degradation, reducing reliability. In addition to internal Joule heat accumulation and exacerbated non-radiative carrier recombination, excessively high laser chip cavity temperature can also reduce the confinement of the quantum wells. When the junction temperature exceeds a certain value, the carrier confinement of the quantum wells decreases by 1-2 orders of magnitude, resulting in a decrease in the slope efficiency of the laser chip. Slope efficiency refers to the ratio of the increase in output optical power to the increase in pump current (or pump power) when the laser chip operates above the threshold current, reflecting the device's efficiency in converting additional electrical energy into optical energy. In addition, during the operation of a high-power semiconductor laser chip, due to the large current injection under normal working conditions, the temperature of the entire cavity will be in a high temperature state, which will in turn increase the temperature of the cavity surface, increase the probability of catastrophic optical damage, and affect the overall performance of the laser chip. Therefore, reducing the cavity temperature of a high-power semiconductor laser chip is very important for improving the output characteristics of a high-power semiconductor laser chip. At present, there are few reports on methods for improving the cavity temperature of a high-power semiconductor laser chip in terms of waveguide design at home and abroad. The mainstream method is still to enhance heat dissipation by improving the packaging, adding external components, etc. Most of them are to reduce the ohmic contact resistance as much as possible to reduce the heat generation of the device and adopt various low thermal resistance packaging methods to enhance heat dissipation to avoid the cavity temperature of the device being too high under large current injection, including the use of flip-chip methods, high thermal conductivity transition heat sink materials, microchannel heat dissipation methods, etc.

[0004] Regarding the flip-chip method. The main heating area of ​​the laser chip is concentrated in an area of ​​several microns on the upper surface. If the P layer is packaged upward and the N layer and the heat sink are connected through solder, the distance between the heating area and the heat sink is too far, and the heat dissipation effect is limited. Therefore, the flip-chip method often improves the internal structure of the laser, adjusts the surface structure of the laser chip and the heating layer of the active area, so that the main heating surface of the chip is directly connected to the heat sink after passing through the solder layer, thereby improving the heat dissipation efficiency. However, the flip-chip method only alleviates the thermal effect caused by the large injection current by shortening the heat dissipation path, and cannot fundamentally solve the problem of cavity heating when the laser chip is working at a high power level.

[0005] Regarding the use of high thermal conductivity transition heat sink materials. At present, high-power semiconductor lasers usually use copper with high thermal conductivity as a heat sink material, but the thermal expansion coefficient of copper is about 2.6 times that of GaAs, resulting in a heat sink shrinkage rate greater than the laser chip during the cooling process. The chip is bent into a convex shape under compressive stress, affecting the output performance of the laser chip. Therefore, a transition heat sink material with high thermal conductivity and a thermal expansion coefficient similar to that of the chip material can be added between the copper and the laser chip, such as tungsten-copper alloy, silicon carbide ceramics, copper-diamond composite materials, graphene films and other materials. However, the current precision processing technology for the high thermal conductivity transition heat sink mentioned above is relatively cumbersome, and its cutting, surface polishing and metallization processing processes are complicated. If the processing does not meet the requirements, the heat dissipation effect may be reduced. At the same time, the high cost of diamond wafer growth and graphene films limits large-scale use.

[0006] Regarding the microchannel heat dissipation method. The microchannel heat sink has a very high heat dissipation efficiency. In order to increase the thermal conductivity of the microchannel, a layer of polycrystalline diamond is usually deposited before the microchannel is metallized, which improves the overall heat dissipation efficiency. Compared with other heat dissipation methods, the cooling medium flowing in the microchannel to dissipate heat can achieve a higher heat transfer coefficient. At the same time, making the microchannel radiator directly inside the chip substrate can ensure that the heat transfer path from the chip heating area to the cooling medium is as short as possible and the volume of the device is as small as possible. Microchannel heat sink heat dissipation can not only achieve a very high heat dissipation capacity, but also realize the integrated packaging manufacturing of the radiator and the chip. However, due to the narrow heat dissipation channel, the microchannel heat sink is prone to cooling medium particles blocking the channel due to thermal deformation and electrochemical corrosion. At the same time, the narrow structure of the microchannel will cause the cooling medium flow resistance to increase significantly, and the heat dissipation effect will decrease.

[0007] In addition, the above-mentioned traditional methods only passively alleviate the high cavity temperature caused by large current injection, and cannot fundamentally solve the problem of excessively high cavity temperature when high-power semiconductor laser chips are working. Summary of the Invention

[0008] The purpose of the present invention is to solve the problem of excessively high cavity temperature during operation of existing high-power semiconductor laser chips. The traditional solution only passively alleviates the high cavity temperature caused by large current injection, but cannot fundamentally solve the technical problem of excessively high cavity temperature during operation of high-power semiconductor laser chips. Instead, a waveguide and semiconductor laser chip are provided to improve the cavity temperature distribution of high-power semiconductor laser chips.

[0009] The design concept of the present invention is as follows: During the operation of a high-power semiconductor laser chip, the temperature of the entire cavity will be in a high temperature state due to the large current injection under normal working conditions, which will in turn increase the temperature of the cavity surface, increase the probability of catastrophic optical damage, and affect the overall performance of the laser chip; therefore, if the cavity length of the laser chip can be extended and the cavity temperature can be improved, the temperature along the length of the laser chip cavity will show a periodic distribution of high and low temperatures, and ultimately reduce the impact of the laser chip self-heating on the junction temperature, it will be possible to more effectively distribute heat and improve the output characteristics of the laser chip.

[0010] To achieve the above-mentioned purpose, according to the design ideas of the above-mentioned invention, the technical solution adopted by the present invention is:

[0011] A waveguide for improving the temperature distribution of a high-power semiconductor laser chip cavity includes an N confinement layer, an N waveguide layer, an active layer, a P waveguide layer, a P confinement layer, and a ridge waveguide arranged from bottom to top. The waveguide has the following features:

[0012] A plurality of transverse isolation grooves are provided on the upper surface of the ridge waveguide, penetrating the ridge waveguide along the width direction of the laser cavity, as an electrically insulating isolation region. The depth of the transverse isolation grooves is defined as D1, the distance from the upper surface of the ridge waveguide to the upper surface of the P confinement layer is defined as D2, and the distance from the upper surface of the ridge waveguide to the lower surface of the P confinement layer is defined as D3. Then, D2 < D1 < D3.

[0013] Multiple lateral isolation grooves divide the ridge waveguide and part of the P confinement layer into multiple window regions and multiple lasing regions;

[0014] Multiple window areas and multiple lasing areas are alternately distributed along the length direction of the laser chip cavity;

[0015] Among the multiple alternately distributed window regions and lasing regions, the first one close to the front cavity surface of the laser chip is set as the lasing region, and a non-injection window is set on the side of the lasing region close to the front cavity surface of the laser chip; or, among the multiple alternately distributed window regions and lasing regions, the first one close to the front cavity surface of the laser chip is set as the window region, and the window region is directly connected to the front cavity surface of the laser chip;

[0016] Multiple window areas are connected to low-voltage electrodes for low-voltage current injection, and multiple lasing areas are connected to high-voltage electrodes for high-voltage current injection; the high voltage is greater than the laser chip threshold voltage, and the low voltage is slightly less than the laser chip threshold voltage.

[0017] Furthermore, the low voltage is defined as V1 and the laser chip threshold voltage is defined as V0;

[0018] The low voltage slightly less than the laser chip threshold voltage means that the condition is met: 95%×V0≤V1≤98%×V0;

[0019] D1, D2, and D3 satisfy D2<D1<D3 and also satisfy the condition: D2+0.45μm≤D1≤D2+0.55μm.

[0020] Furthermore, the electrically insulating isolation region further includes a plurality of longitudinal isolation grooves provided at the edge of the upper surface of the ridge waveguide, and the depth of the longitudinal isolation grooves is defined as D4, then D4=D1;

[0021] Both ends of each transverse isolation groove are connected to one end of a longitudinal isolation groove, and the two longitudinal isolation grooves connected to the same transverse isolation groove are respectively located on both sides of the transverse isolation groove, and two adjacent transverse isolation grooves are connected through a longitudinal isolation groove.

[0022] Furthermore, the electrically insulating isolation region is formed by the following method:

[0023] An etching process is used on the ridge waveguide and part of the P confinement layer to etch out a transverse isolation groove and a longitudinal isolation groove to form an electrically insulating isolation region;

[0024] The width of the transverse isolation groove and the longitudinal isolation groove are both 1.5 μm-2.5 μm.

[0025] Furthermore, the width of the transverse isolation trench and the longitudinal isolation trench are both 2 μm, and D1 = D2 + 0.5 μm.

[0026] Furthermore, along the cavity length direction of the laser chip, from the front cavity surface of the laser chip to the back cavity surface of the laser chip, the lengths of the plurality of window areas decrease in sequence, and the lengths of the plurality of lasing areas increase in sequence.

[0027] Furthermore, it is defined that along the laser chip cavity length direction, from the laser chip front cavity surface to the laser chip back cavity surface, the ridge waveguide and part of the P confinement layer are divided into N periodic units W arranged in sequence. n , each period unit W n Each contains a lasing region and a window region, and each period unit W n The lengths of the two nodes are equal, where N≥2, n=1, 2……N.

[0028] Furthermore, the total length of all lasing regions = the total length of all window regions;

[0029] Along the laser chip cavity length direction, from the laser chip front cavity surface to the laser chip back cavity surface, the lengths of the plurality of window areas decrease in sequence, and the lengths of the plurality of lasing areas increase in sequence.

[0030] Furthermore, along the length of the laser chip cavity, the length of the N confinement layer, N waveguide layer, active layer, P waveguide layer, and P confinement layer are all 6 mm, and the width is 400 μm;

[0031] The ridge waveguide has a width of 100 μm and a length of 5.8 mm. Non-injection windows are set on both sides of the ridge waveguide along the length of the laser chip cavity. The length of the two non-injection windows is 100 μm.

[0032] N=20; each period unit W n The length along the laser chip cavity length direction is equal to 290 μm. In the periodic unit W1, the length of the lasing region is 13 μm and the length of the window region is 273 μm. Along the laser chip cavity length direction, from the front cavity surface of the laser chip to the back cavity surface of the laser chip, the lengths of the multiple lasing regions increase by 13 μm, and the lengths of the multiple window regions decrease by 13 μm.

[0033] The high voltage is 1.76V and the low voltage is 1.55V.

[0034] The present invention further provides a semiconductor laser chip comprising a GaAs substrate and a waveguide disposed above the GaAs substrate; the semiconductor laser chip is characterized in that:

[0035] The waveguide adopts the waveguide for improving the temperature distribution of the high-power semiconductor laser chip cavity.

[0036] Compared with the prior art, the present invention has the following beneficial technical effects:

[0037] 1. The present invention provides a waveguide and semiconductor laser chip for improving the cavity temperature distribution of a high-power semiconductor laser chip. The waveguide and a portion of the P confinement layer are divided into multiple window regions and multiple lasing regions, which are alternately distributed along the length of the laser chip cavity, through an electrically insulating isolation region. Separate current injection control is performed on the window regions and the lasing regions, respectively, so that the lasing region generates output power when a high voltage is applied, while the window region remains transparent when a low voltage slightly less than a threshold voltage is applied. This ensures minimal optical loss and cavity heat dissipation, thereby improving cavity heat dissipation while ensuring output power, reducing the cavity temperature and front cavity surface temperature of the laser chip, achieving a more uniform temperature distribution, and improving the output performance of the laser chip.

[0038] 2. The present invention provides a waveguide and semiconductor laser chip for improving the cavity temperature distribution of a high-power semiconductor laser chip. An etching process is used to form an electrically insulating isolation region on the ridge waveguide and a portion of the P confinement layer. The shape of the electrically insulating isolation region is determined by a mask. Therefore, the design of the electrically insulating isolation region can be achieved by designing the mask. This technical process is extremely mature, and therefore the manufacturing process of the present invention is fully compatible with existing processes.

[0039] 3. The present invention provides a waveguide and semiconductor laser chip for improving the cavity temperature distribution of a high-power semiconductor laser chip. The waveguide and semiconductor laser chip are configured by setting the first one close to the front cavity surface of the laser chip as a lasing zone among a plurality of alternately distributed window zones and lasing zones, and setting a non-injection window on the side of the lasing zone close to the front cavity surface of the laser chip. Alternatively, the first one close to the front cavity surface of the laser chip is set as a window zone among a plurality of alternately distributed window zones and lasing zones, and the window zone is directly connected to the front cavity surface of the laser chip, so that the laser zone is as far away from the front cavity surface of the laser chip as possible. A plurality of transparent windows are introduced near the front cavity surface of the laser chip, and the passive part is introduced into the cavity surface, which effectively reduces the heat load of the front cavity surface of the laser chip. While improving the cavity temperature distribution and cavity heat dissipation of the laser chip, the probability of catastrophic optical damage (COD) is reduced, thereby achieving the effect of improving the reliability of the high-power semiconductor laser chip.

[0040] 4. The present invention provides a waveguide and semiconductor laser chip for improving the temperature distribution in the cavity of a high-power semiconductor laser chip. By arranging along the length of the laser chip cavity, from the front cavity surface to the rear cavity surface of the laser chip, the lengths of all window areas decrease in sequence, and the lengths of all lasing areas increase in sequence, so that the current injection into the front half of the laser chip cavity is mainly into the window area, and the current injection into the rear half of the cavity is mainly into the lasing area. This can reduce photon accumulation on the front cavity surface of the laser chip and ensure the continuity of laser emission in the laser chip cavity.

[0041] 5. The present invention provides a waveguide and semiconductor laser chip for improving the cavity temperature distribution of a high-power semiconductor laser chip. By isolating two different electric injection regions, namely the window region and the lasing region, the waveguide and semiconductor laser chip are electrically isolated. This can increase the cavity length of the laser chip while ensuring the output power, thus breaking through the cavity length limitation of traditional high-power semiconductor laser chips. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of the cross-sectional structure of an embodiment of a semiconductor laser chip according to the present invention, perpendicular to the length of the laser chip cavity (the figure shows the electrode sheet and the insulating layers grown on both sides of the ridge waveguide);

[0043] Figure 2Schematic diagram of the three-dimensional structure of a semiconductor laser chip embodiment of the present invention (the figure shows the insulating layers grown on both sides of the ridge waveguide);

[0044] Figure 3 This is a schematic cross-sectional view of a semiconductor laser chip embodiment of the present invention perpendicular to the laser chip cavity width direction (the electrode sheet is shown in the figure);

[0045] Figure 4 A schematic diagram of the electrode structure used in an embodiment of the semiconductor laser chip of the present invention;

[0046] Figure 5 This is a comparison of experimental results of the electron density distribution along the cavity length of the semiconductor laser chip embodiment of the present invention and a semiconductor laser chip using a conventional waveguide;

[0047] Figure 6 This is a comparison chart of experimental results of the distribution of photon density along the cavity length of a semiconductor laser chip embodiment of the present invention and a semiconductor laser chip using a conventional waveguide;

[0048] Figure 7 This is a comparison of experimental results of the distribution of absorbed heat along the cavity length of a semiconductor laser chip embodiment of the present invention and a semiconductor laser chip using a conventional waveguide;

[0049] Figure 8 This is a comparison of experimental results of the Joule heat distribution along the laser chip cavity length direction for an embodiment of the semiconductor laser chip of the present invention and a semiconductor laser chip using a conventional waveguide;

[0050] Figure 9 This is a comparison of experimental results of the distribution of non-radiative recombination heat along the cavity length of a semiconductor laser chip embodiment of the present invention and a semiconductor laser chip using a conventional waveguide;

[0051] Figure 10 This is a comparison chart of experimental results of the total cavity temperature distribution along the cavity length direction of the semiconductor laser chip embodiment of the present invention and a semiconductor laser chip using a conventional waveguide.

[0052] The following are the descriptions of the reference numerals:

[0053] 01-GaAs substrate, 02-N confinement layer, 03-N waveguide layer, 04-active layer, 05-P waveguide layer, 06-P confinement layer, 07-ridge waveguide, 08-electrode sheet, 09-insulating layer;

[0054] 1-electrically insulating isolation region, 11-lateral isolation groove, 12-longitudinal isolation groove, 2-window region, 3-lasing region, 4-non-injection window, 5-electrode electrically insulating isolation region, 6-low voltage region, 7-high voltage region, 8-insulating region, S1-front cavity surface of laser chip. DETAILED DESCRIPTION

[0055] To make the objects, advantages and features of the present invention more clear, the waveguide and semiconductor laser chip for improving the cavity temperature distribution of a high-power semiconductor laser chip proposed by the present invention are further described in detail below with reference to the accompanying drawings and specific embodiments.

[0056] The cavity self-heating in high-power semiconductor laser chips increases the junction temperature. The increase in junction temperature will lead to a decrease in the recombination efficiency of electrons and holes, directly reducing the output power and brightness of the laser chip. At the same time, the increase in junction temperature will cause the lattice expansion and band structure change of the semiconductor material, causing the emission wavelength to move toward the long-wave direction (red shift). Therefore, reducing the laser chip cavity temperature is very important for improving the output characteristics of the laser chip.

[0057] Figure 1 This is a schematic cross-sectional view of the semiconductor laser chip embodiment of the present invention perpendicular to the laser chip cavity length direction, showing the insulating layer 09 grown on both sides of the ridge waveguide 07, and the electrode sheet 08 set on top of the ridge waveguide 07 and the insulating layer 09. Figure 1 The semiconductor laser chip of the present invention includes a GaAs substrate 01 and a waveguide arranged above the GaAs substrate 01 to improve the temperature distribution of the high-power semiconductor laser chip cavity. The waveguide for improving the temperature distribution of the high-power semiconductor laser chip cavity includes an N confinement layer 02, an N waveguide layer 03, an active layer 04, a P waveguide layer 05, a P confinement layer 06 and a ridge waveguide 07 arranged from bottom to top. In order to comply with the current mainstream packaging technology, the N confinement layer 06 is arranged along the length direction of the laser chip cavity. The lengths of the N waveguide layer 02, N waveguide layer 03, active layer 04, P waveguide layer 05 and P confinement layer 06 are all 6 mm, the widths of the N confinement layer 02, N waveguide layer 03, active layer 04, P waveguide layer 05 and P confinement layer 06 are all 400 μm, the width of the ridge waveguide 07 is 100 μm, the length of the ridge waveguide 07 is 5.8 mm, and non-injection windows 4 are provided on both sides of the ridge waveguide 07 along the length direction of the laser chip cavity. The lengths of the two non-injection windows 4 are both 100 μm.

[0058] like Figure 2 and Figure 3As shown, a plurality of transverse isolation grooves 11 are provided on the upper surface of the ridge waveguide 07 along the width direction of the laser cavity, which serve as an electrical insulation isolation region 1. The size of the transverse isolation groove 11 along the width direction of the laser cavity is equal to the width of the ridge waveguide 07. The electrical insulation isolation region 1 also includes a plurality of longitudinal isolation grooves 12 provided at the edge of the upper surface of the ridge waveguide 07. The two ends of each transverse isolation groove 11 are connected to one end of a longitudinal isolation groove 12, and the two longitudinal isolation grooves 12 connected to the same transverse isolation groove 11 are respectively located on both sides of the transverse isolation groove 11, and two adjacent transverse isolation grooves 11 are connected by a longitudinal isolation groove 12. The depth of the transverse isolation groove 11 is defined as D1, the distance from the upper surface of the ridge waveguide 07 to the upper surface of the P restriction layer 06 is defined as D2, the distance from the upper surface of the ridge waveguide 07 to the lower surface of the P restriction layer 06 is defined as D3, and the depth of the longitudinal isolation groove 12 is defined as D4. Then, D2<D1<D3, D4=D1. The widths of the transverse isolation groove 11 and the longitudinal isolation groove 12 in this embodiment are both 2μm, D4=D1=D2+0.5μm; the electrically insulating isolation region 1 divides the ridge waveguide 07 and part of the P restriction layer 06 into multiple window regions 2 and multiple lasing regions 3, and the multiple window regions 2 and the multiple lasing regions 3 are alternately distributed along the length direction of the laser chip cavity.

[0059] Multiple window areas 2 are connected to low voltage electrodes for low voltage current injection. The low voltage is slightly lower than the threshold voltage of the laser chip. The low voltage in this embodiment is 1.55V. Multiple laser areas 3 are connected to high voltage electrodes for high voltage current injection. The high voltage is higher than the threshold voltage of the laser chip, but does not exceed the maximum voltage that the semiconductor laser chip can withstand under normal working conditions. The high voltage in this embodiment is 1.76V. The electrode sheet used by the semiconductor laser chip in this embodiment is as follows: Figure 4 As shown, the low-voltage electrode and the high-voltage electrode are designed as an electrode sheet 08 with an integrated structure. Insulating areas 8 corresponding to the non-injection windows 4 are provided at both ends of the electrode sheet 08. An electrode electrically insulating isolation area 5 corresponding to the electrically insulating isolation area 1 is etched on the electrode sheet 08. The depth of the electrode electrically insulating isolation area 5 is equal to the thickness of the electrode sheet 08. The electrode electrically insulating isolation area 5 divides the electrode sheet 08 into a low-voltage area 6 and a high-voltage area 7. The low-voltage area 6 is connected to the above-mentioned multiple window areas 2 for low-voltage current injection, and the high-voltage area 7 is connected to the above-mentioned multiple lasing areas 3 for high-voltage current injection.

[0060] The present invention changes the waveguide design of the high-power semiconductor laser chip and proposes a new GaAs-based distributed waveguide for a high-power semiconductor laser chip with a certain epitaxial structure. By designing an electrically insulating isolation region 1, the ridge waveguide 07 and part of the P confinement layer 06 are divided into a plurality of alternately distributed window regions 2 and a plurality of lasing regions 3. The lasing regions 3 are set to apply a high voltage for normal laser output, and a low voltage is applied to the window region 2 to act as a transparent window. This can enhance the heat dissipation of the cavity while guiding the light beam with minimal internal loss, thereby achieving the same power output compared to the conventional laser region 1. Compared with conventional waveguide designs, this method significantly reduces cavity temperature, reduces the thermal power density of the laser chip's front cavity surface S1, suppresses the shrinkage of the laser chip's front cavity surface S1 material bandgap caused by increased junction temperature, achieves a lower laser chip front cavity surface S1 temperature, and obtains a more uniform temperature distribution, improving the output performance of the semiconductor laser chip. Furthermore, the cavity length of the laser chip can be extended while maintaining the same power output, making the present invention's waveguide for improving cavity temperature distribution in high-power semiconductor laser chips applicable to any cavity length size of high-power semiconductor laser chips, thus breaking through the limitations of traditional laser cavity lengths. By introducing a window region and increasing the transparent portion of the device's waveguide design, the present invention can fundamentally address the high-temperature problem of the high-power semiconductor laser chip cavity.

[0061] It should be noted that the laser chip front cavity surface S1 refers to the cavity surface on the semiconductor laser chip that emits laser light.

[0062] Define the low voltage as V1 and the laser chip threshold voltage as V0. A low voltage slightly less than the laser chip threshold voltage satisfies the following condition: 95% × V0 ≤ V1 ≤ 98% × V0. The low voltage applied to window region 2 should not be too low, otherwise the beam guidance effect will be inadequate and losses within the cavity will be excessive. It should also not be too high, otherwise the effect of improving cavity temperature distribution will be reduced.

[0063] like Figure 2As shown, among the multiple alternately distributed window areas 2 and lasing areas 3, the first one close to the front cavity surface S1 of the laser chip is set as the lasing area 3, and a non-injection window 4 is set on the side of the lasing area 3 close to the front cavity surface S1 of the laser chip. By setting the non-injection window 4, more transparent windows are introduced near the front cavity surface S1 of the laser chip, so that the lasing area 3 is as far away from the front cavity surface S1 of the laser chip as possible, which can effectively reduce the heat load of the front cavity surface S1 of the laser chip, improve the temperature distribution of the laser chip cavity, and reduce the probability of COD generation, thereby improving the reliability of the high-power semiconductor laser chip. In other embodiments, the first one close to the front cavity surface S1 of the laser chip can be set as the window zone 2 among the multiple alternatingly distributed window zones 2 and lasing zones 3, and the window zone 2 can be directly connected to the front cavity surface S1 of the laser chip, that is, no non-injection window 4 is used between the front cavity surface S1 of the laser chip and the window zone 2. By adjusting the positions of the window zone 2 and the lasing zone 3, a transparent window can also be introduced near the front cavity surface S1 of the laser chip, thereby achieving the purpose of improving heat dissipation and increasing the COD effect threshold.

[0064] In order to reduce the photon accumulation on the front cavity surface S1 of the laser chip and ensure the continuity of laser emission in the laser chip cavity, a current injection area with a non-uniform shape is selected for etching, such as Figure 2 and Figure 3 As shown, along the laser chip cavity length, from the laser chip front cavity surface S1 to the laser chip back cavity surface, the lengths of the multiple window regions 2 decrease in sequence, while the lengths of the multiple lasing regions 3 increase in sequence. This makes the cavity current injection area in the front half of the laser chip mainly the window region 2, while the cavity current injection area in the back half is mainly the lasing region 3. This arrangement also helps improve the temperature distribution of the laser chip cavity.

[0065] Definition: Along the laser chip cavity length direction, from the laser chip front cavity surface S1 to the laser chip back cavity surface, the ridge waveguide 07 and part of the P confinement layer 06 are divided into N periodic units W arranged in sequence. n , where N≥2, n=1, 2...N, in this embodiment, N=20, and 20 periodic units W are designed in the cavity. n To enhance heat dissipation, each cycle unit W n Each of them contains a lasing region 3 and a window region 2. Without neglecting the width of the electrically insulating isolation region 1, each periodic unit W n The length of the laser chip along the cavity length direction is equal to 290μm. In the periodic unit W1, the length of the lasing area 3 is 13μm and the length of the window area 2 is 273μm. Along the cavity length direction of the laser chip, from the front cavity surface S1 of the laser chip to the back cavity surface of the laser chip, the lengths of the multiple lasing areas 3 increase by 13μm in sequence, and the lengths of the multiple window areas 2 decrease by 13μm in sequence. The periodic unit W 11The lengths of the middle window region 2 and the lasing region 3 are equal, and ultimately the total length of all lasing regions 3 is equal to the total length of all window regions 2, and the ratio of the total length of all window regions 2 to the waveguide length is the same as the ratio of the total length of all lasing regions 3 to the waveguide length.

[0066] In other embodiments, the shape, proportion and number of the window region 2 and the lasing region 3 can be adjusted by designing the electrically insulating isolation region 1. For example, the time required for each periodic unit W can be shortened. n The length of the inner window area 2 increases the total proportion of the effective light-emitting part to the cavity length and adjusts the cavity length; for example, N can be set to 10, 14, 16, 18, 22, 25, 30, etc.

[0067] The electrically insulating isolation region 1 is formed by etching the ridge waveguide 07 and a portion of the P confinement layer 06 to form a transverse isolation trench 11 and a longitudinal isolation trench 12. The shape of the electrically insulating isolation region 1 is determined by the mask, and thus, the mask design can be used to design the electrically insulating isolation region 1. This process is highly mature, and the waveguide manufacturing process of the present invention is fully compatible with existing processes.

[0068] In other embodiments, D1, D2, and D3 can be set to satisfy D2 < D1 < D3 while also satisfying the condition: D2 + 0.45 μm ≤ D1 ≤ D2 + 0.55 μm. The depth of the electrically insulating isolation region 1 should not be too small, otherwise the injected current will enter the active region and diverge, resulting in poor isolation. The depth of the electrically insulating isolation region 1 should also not be too large, otherwise it will affect the beam guidance effect within the cavity.

[0069] In other embodiments, the widths of the transverse isolation trench 11 and the longitudinal isolation trench 12 may both be set to 1.5 μm-2.5 μm. The widths of the transverse isolation trench 11 and the longitudinal isolation trench 12 should not be too small, otherwise the current isolation effect will be poor. The widths of the transverse isolation trench 11 and the longitudinal isolation trench 12 should not be too large, otherwise the proportion of the cavity light-emitting portion will be reduced, affecting the overall luminous efficiency of the laser. In other embodiments, the longitudinal isolation trench 12 may not be provided, but the electrode electrically insulating isolation region 5 must be provided on the electrode sheet 08.

[0070] The technical effects of the present invention are further explained below through experiments and data:

[0071] Since only 3 mm of the cavity length in the semiconductor laser chip of this embodiment actively generates lasing, the experimental results are compared with those of a semiconductor laser chip with a 3 mm cavity length and a conventional waveguide (with the same non-injection window length, the same waveguide width, and an applied voltage of 1.76 V) to ensure a fair evaluation.

[0072] Experimental results and analysis:

[0073] Under the premise of outputting 10W optical power, Figures 5 to 9 The experimental results of the distribution of electron density, photon density, absorption heat, Joule heat, and non-radiative recombination heat along the cavity length of the semiconductor laser chip of the present invention and that of a semiconductor laser chip using a conventional waveguide are compared. As can be seen from the figure, the electron density of the semiconductor laser chip of the present invention is more evenly distributed along the cavity length of the laser chip, and the photon density shows a trend of first increasing and then decreasing along the cavity length of the laser chip. The maximum photon density is located at the cavity length of 2.87 mm instead of near the front cavity surface S1 of the laser chip. In addition, the average photon density is increased by 2.21×10 15 cm -3 ; The semiconductor laser chip of the present invention has a heat absorption power of 7.96 W / cm2 on the front cavity surface S1 of the laser chip, which is only 48.8% of the value of the semiconductor laser chip using conventional waveguides; the Joule heat power of the semiconductor laser chip of the present invention is more evenly distributed along the cavity length of the laser chip, with an average value of 1.02 W / cm2; the semiconductor laser chip of the present invention has a maximum non-radiative composite heat power of 2.55 W / cm2 along the cavity length of the laser chip, and a total non-radiative composite heat power of 0.978 W. The non-radiative composite heat power of the semiconductor laser chip using conventional waveguides has a maximum non-radiative composite heat power of 5.31 W / cm2 along the cavity length of the laser chip, and a total non-radiative composite heat power of 1.48 W.

[0074] The experimental results of the total cavity temperature distribution along the laser chip cavity length are as follows: Figure 10 As shown, when the same optical power is output, the maximum temperature of the entire cavity of the semiconductor laser chip of the present invention is 39.53°C, which is 12.28°C lower than the maximum temperature of 51.81°C of the semiconductor laser chip using conventional waveguide; the temperature of the front cavity surface S1 of the semiconductor laser chip of the present invention is 34.98°C, which is 11.64°C lower than the front cavity surface temperature of the semiconductor laser chip using conventional waveguide; the average temperature of the semiconductor laser chip along the cavity length direction of the laser chip of the present invention is 35.65°C, and the standard deviation of the cavity temperature is 1.508. The average temperature of the semiconductor laser chip along the cavity length direction of the semiconductor laser chip using conventional waveguide is 46.43°C, and the standard deviation of the cavity temperature is 3.375. Therefore, under the condition of the same output power, compared with conventional waveguide designs, the waveguide of the present invention for improving the temperature distribution of the cavity of a high-power semiconductor laser chip has a more obvious improvement on the temperature of the front cavity surface of the laser chip and the heat dissipation of the cavity, which is beneficial to reducing the probability of catastrophic optical damage (COD) on the cavity surface, improving the output characteristics of the high-power semiconductor laser chip, and in addition, it can also increase the cavity length.

[0075] Starting from the waveguide design of the laser chip, the present invention designs a distributed waveguide structure that uses an alternating integration of a lasing region 3 and a window region 2. Alternating lasing regions and window regions are integrated in a cavity, and independent current injection control of the two regions is achieved through electrical insulation isolation technology. The lasing region 3 operates in a high current injection state to generate laser output, and the window region 2 remains transparent under the current injection of a subthreshold current (slightly below the threshold). Compared with conventional waveguide designs, the present invention reduces the thermal power density of the front cavity surface S1 of the laser chip while improving the cavity temperature distribution, suppresses the band gap contraction of the front cavity surface material caused by temperature rise, and achieves a lower cavity temperature and front cavity surface temperature than conventional waveguide design laser chips, improves the output characteristics of high-power semiconductor laser chips and reduces the probability of cavity surface optical catastrophic damage (COD) effect. The present invention is applicable to any cavity length size of high-power semiconductor laser chips and can break through the cavity length limit of traditional laser chips. The chip manufacturing process involved in the present invention is fully compatible with existing processes. In the manufacturing process of semiconductor laser chips, photolithography is required to form an electric injection window, the shape of which is determined by the mask. Therefore, the design of current injection can be achieved by designing the mask. This technical process is extremely mature, so the manufacturing process designed by the present invention is fully compatible with existing processes.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the specific technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present invention.

Claims

1. A waveguide for improving the temperature distribution of a high-power semiconductor laser chip cavity, comprising an N confinement layer (02), an N waveguide layer (03), an active layer (04), a P waveguide layer (05), a P confinement layer (06) and a ridge waveguide (07) arranged from bottom to top; characterized in that: A plurality of transverse isolation grooves (11) are provided on the upper surface of the ridge waveguide (07) and penetrate the ridge waveguide (07) along the width direction of the laser cavity, serving as an electrically insulating isolation region (1); the depth of the transverse isolation grooves (11) is defined as D1, the distance from the upper surface of the ridge waveguide (07) to the upper surface of the P confinement layer (06) is defined as D2, and the distance from the upper surface of the ridge waveguide (07) to the lower surface of the P confinement layer (06) is defined as D3, and D2<D1<D3; The plurality of transverse isolation grooves (11) divide the ridge waveguide (07) and a portion of the P confinement layer (06) into a plurality of window regions (2) and a plurality of lasing regions (3); The plurality of window regions (2) and the plurality of lasing regions (3) are alternately distributed along the length direction of the laser chip cavity; Among a plurality of alternately distributed window areas (2) and lasing areas (3), the first one close to the front cavity surface (S1) of the laser chip is set as the lasing area (3), and a non-injection window (4) is set on a side of the lasing area (3) close to the front cavity surface (S1) of the laser chip; or, among a plurality of alternately distributed window areas (2) and lasing areas (3), the first one close to the front cavity surface (S1) of the laser chip is set as the window area (2), and the window area (2) is directly connected to the front cavity surface (S1) of the laser chip; The plurality of window areas (2) are all connected to low-voltage electrodes for low-voltage current injection, and the plurality of lasing areas (3) are all connected to high-voltage electrodes for high-voltage current injection; the high voltage is greater than the laser chip threshold voltage, and the low voltage is slightly less than the laser chip threshold voltage.

2. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 1, characterized in that: The low voltage is defined as V1 and the laser chip threshold voltage is defined as V0; The low voltage being slightly less than the laser chip threshold voltage means that the condition is satisfied: 95%×V0≤V1≤98%×V0; The D1, D2, and D3 satisfy D2<D1<D3 and also satisfy the condition: D2+0.45μm≤D1≤D2+0.55μm.

3. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 2, characterized in that: The electrically insulating isolation region (1) further comprises a plurality of longitudinal isolation grooves (12) arranged at the edge of the upper surface of the ridge waveguide (07), and the depth of the longitudinal isolation grooves (12) is defined as D4, then D4=D1; Both ends of each transverse isolation groove (11) are connected to one end of a longitudinal isolation groove (12), and the two longitudinal isolation grooves (12) connected to the same transverse isolation groove (11) are respectively located on both sides of the transverse isolation groove (11), and two adjacent transverse isolation grooves (11) are connected through one longitudinal isolation groove (12).

4. The waveguide for improving the temperature distribution of a high-power semiconductor laser chip cavity according to claim 3, characterized in that: The electrically insulating isolation region (1) is formed by the following method: Using an etching process on the ridge waveguide (07) and a portion of the P confinement layer (06), etching the transverse isolation groove (11) and the longitudinal isolation groove (12) to form the electrically insulating isolation region (1); The widths of the transverse isolation groove (11) and the longitudinal isolation groove (12) are both 1.5 μm-2.5 μm.

5. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 4, characterized in that: The width of the transverse isolation groove (11) and the longitudinal isolation groove (12) are both 2 μm, and D1 = D2 + 0.5 μm.

6. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to any one of claims 1 to 5, characterized in that: Along the laser chip cavity length direction, from the laser chip front cavity surface (S1) to the laser chip back cavity surface, the lengths of the plurality of window areas (2) decrease in sequence, and the lengths of the plurality of lasing areas (3) increase in sequence.

7. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 6, characterized in that: It is defined that along the laser chip cavity length direction, from the laser chip front cavity surface (S1) to the laser chip back cavity surface, the ridge waveguide (07) and part of the P confinement layer (06) are divided into N periodic units W arranged in sequence n , each of the periodic units W n Each of the periodic units W comprises a laser region (3) and a window region (2), and each of the periodic units W n The lengths of the two nodes are equal, where N≥2, n=1, 2……N.

8. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 7, characterized in that: The total length of all the lasing regions (3) = the total length of all the window regions (2); Along the laser chip cavity length direction, from the laser chip front cavity surface (S1) to the laser chip back cavity surface, the lengths of the plurality of window areas (2) decrease in sequence with equal differences, and the lengths of the plurality of lasing areas (3) increase in sequence with equal differences.

9. The waveguide for improving the temperature distribution in the cavity of a high-power semiconductor laser chip according to claim 8, characterized in that: Along the length direction of the laser chip cavity, the lengths of the N confinement layer (02), the N waveguide layer (03), the active layer (04), the P waveguide layer (05) and the P confinement layer (06) are all 6 mm, and the widths are all 400 μm; The width of the ridge waveguide (07) is 100 μm and the length is 5.8 mm; the ridge waveguide (07) is provided with non-injection windows (4) on both sides along the length direction of the laser chip cavity, and the length of the two non-injection windows (4) is 100 μm; N=20; each period unit W n The lengths along the cavity length direction of the laser chip are all equal to 290 μm; in the periodic unit W1, the length of the lasing region (3) is 13 μm, the length of the window region (2) is 273 μm, and along the cavity length direction of the laser chip, from the front cavity surface (S1) of the laser chip to the back cavity surface of the laser chip, the lengths of the plurality of lasing regions (3) increase by 13 μm in sequence, and the lengths of the plurality of window regions (2) decrease by 13 μm in sequence; The high voltage is 1.76V, and the low voltage is 1.55V.

10. A semiconductor laser chip comprising a GaAs substrate (01) and a waveguide arranged above the GaAs substrate (01); characterized in that: The waveguide is the waveguide for improving the temperature distribution of the high-power semiconductor laser chip cavity as described in any one of claims 1 to 9.

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