A low divergence angle wide stripe type high power semiconductor laser adopting a backward waveguide effect

Abstract

This invention discloses a low-divergence-angle, wide-strip high-power semiconductor laser employing an anti-waveguide effect, belonging to the field of semiconductor laser technology. The current injection region is groove-shaped, formed by etching away all undoped GaAs layers and part of a highly doped GaAs ohmic contact layer. Both sides of the current injection region are covered with an ultra-thick insulating layer. The anti-waveguide effect is achieved through the undoped GaAs layer and the groove-shaped current injection region, filtering out higher-order modes of light. Only light perpendicular to the cavity surfaces at both ends can undergo F-P oscillation, amplification, and laser output, thus significantly reducing the slow-axis divergence angle. Simultaneously, the insulating material on both sides of the current injection region effectively reduces heat dissipation efficiency, thereby effectively eliminating the thermal lensing effect and preventing the chip from reforming the waveguide effect due to thermal lensing in high-power operation mode. This further reduces the slow-axis divergence angle of the chip in high-power operation mode, effectively improving the beam quality of the wide-strip semiconductor laser.

Description

Technical Field

[0001] This invention relates to a low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect, belonging to the field of semiconductor laser technology. Background Technology

[0002] Wide-strip high-power semiconductor lasers have seen continuous development due to their high output power, simple fabrication and packaging processes, and ease of integration and mass production, finding wide applications, particularly in laser cutting, medical aesthetics, and industrial pumping. Typically, wide-strip high-power semiconductor lasers employ a ridge process, where current flows through the ridge into the active region and undergoes radiative recombination to generate photons. However, with the continuous development of industries and other fields, higher demands are being placed on the beam quality of wide-strip lasers, especially on the slow-axis divergence angle. However, due to inherent defects in the ridge process and the thermal lensing effect, the slow-axis divergence angle of current wide-strip high-power semiconductor lasers cannot be further optimized.

[0003] Chinese patent CN104332823A discloses "A method for improving the beam quality of a wide-strip high-power semiconductor laser." This method primarily improves the beam quality and reduces the slow-axis divergence angle of the wide-strip high-power semiconductor laser by applying tensile stress with a convex intensity distribution to the wide-strip high-power semiconductor laser chip. This reduces the convex refractive index distribution caused by the waveguide deconvexity temperature distribution, suppresses the thermal lensing effect of the laser waveguide, and thus improves the beam quality of the wide-strip high-power semiconductor laser. However, the inventors have found that this method requires introducing solder pads into the chip edge region through packaging and applying pressure to the middle of the chip during the soldering process. This results in low packaging efficiency and low yield, making it unsuitable for mass production. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a low-divergence-angle, wide-strip high-power semiconductor laser employing an anti-waveguide effect. The semiconductor laser chip structure provided by this invention etches the ridge region of the original wide-strip high-power semiconductor laser to a certain depth, making the refractive index of this region lower than that of the sides, thereby forming an anti-waveguide effect. This method significantly reduces the full-axis divergence angle. Simultaneously, a thick insulating film is fabricated on both sides to reduce heat dissipation efficiency, effectively eliminating the thermal lensing effect and further reducing the full-axis divergence angle in high-power operation. This invention does not change the subsequent packaging process; conventional packaging methods can be used, improving chip performance while maintaining chip production efficiency.

[0005] The technical solution of the present invention is as follows:

[0006] A low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect comprises, from bottom to top, an N-plane metal layer, a substrate, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a highly doped GaAs ohmic contact layer, an undoped GaAs layer, an insulating layer, and a P-plane metal layer. Above this is a laser chip current injection region, which is groove-shaped and formed by etching away all the undoped GaAs layer and part of the highly doped GaAs ohmic contact layer. Both sides of the groove-shaped current injection region are covered with an ultra-thick insulating layer. A P-plane metal electrode layer covers the insulating layer and the highly doped GaAs ohmic contact layer.

[0007] Preferably, the groove-shaped current injection region is prepared by a wet etching process, and its sidewalls have an angle with the horizontal plane, forming a slope.

[0008] Furthermore, the slope is primarily for metal cladding, and based on current data, an angle range of 30° to 60° is optimal.

[0009] Preferably, the groove-shaped current injection region etches away all the undoped GaAs layer and part of the highly doped GaAs ohmic contact layer, and the groove-shaped current injection region etches 100nm to 200nm of the highly doped GaAs ohmic contact layer.

[0010] Preferably, the thickness of the undoped GaAs layer is 200–400 nm.

[0011] Preferably, the thickness of the highly doped GaAs ohmic contact layer is 400–500 nm.

[0012] Preferably, the insulating layer material is a SiO2 layer or a Si3N4 layer.

[0013] Preferably, the insulating layer material is grown using PECVD and the insulating layer in the current injection region is etched away.

[0014] Preferably, the thickness of the insulating layer material is greater than that of the insulating layer material commonly used in conventional semiconductor lasers, and is 300-700 nm.

[0015] More preferably, the thickness of the insulating layer is maintained between 300 nm and 500 nm. This thickness exceeds that of the insulating layer in conventional semiconductor laser chips, which helps to reduce heat dissipation at the edge of the ridge and eliminate the thermal lensing effect in high-power operating modes.

[0016] Preferably, the substrate material includes any one of GaAs, SiC, SiN, GaN, and InP.

[0017] Preferably, the material of the N-face metal includes any one of AuGeNi and TiPtAu.

[0018] Preferably, the width of the bottom of the current injection region is 190μm to 300μm.

[0019] The beneficial effects of this invention are as follows:

[0020] The semiconductor laser chip provided by this invention achieves an anti-waveguide effect between the light-emitting region and its two sides by fabricating a groove-shaped current injection region. This anti-waveguide effect filters out higher-order modes of light, allowing only light perpendicular to the cavity surfaces at both ends to undergo FP oscillation, amplify, and generate laser light for output, thereby significantly reducing the slow-axis divergence angle. Simultaneously, an ultra-thick insulating layer is fabricated on both sides of the current injection region to reduce heat dissipation efficiency, effectively eliminating the thermal lensing effect and preventing the chip from reforming the waveguide effect under high-power operation. This further reduces the slow-axis divergence angle of the chip under high-power operation, effectively improving the beam quality of the wide-strip semiconductor laser. Attached Figure Description

[0021] Figure 1 This is a schematic cross-sectional view of a low-divergence-angle, wide-strip high-power semiconductor laser chip employing the anti-waveguide effect.

[0022] The numbers in the diagram represent the following components: 1-P-plane metal, 2-insulating layer, 3-undoped GaAs layer, 4-highly doped GaAs ohmic contact layer, 5-P-type confinement layer, 6-P-type waveguide layer, 7-active layer, 8-N-type waveguide layer, 9-N-type confinement layer, 10-substrate, 11-N-plane metal. Detailed Implementation

[0023] The present invention will be further described below with reference to the embodiments and accompanying drawings, but is not limited thereto.

[0024] Example 1:

[0025] A low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect comprises, from bottom to top, an N-plane metal layer 11, a substrate 10, an N-type confinement layer 9, an N-type waveguide layer 8, an active layer 7, a P-type waveguide layer 6, a P-type confinement layer 5, a highly doped GaAs ohmic contact layer 4, an undoped GaAs layer 3, an insulating layer 2, and a P-plane metal layer 1. Above this is a laser chip current injection region, which is groove-shaped and formed by etching away all the undoped GaAs layer and part of the highly doped GaAs ohmic contact layer. Both sides of the groove-shaped current injection region are covered with an ultra-thick insulating layer. A P-plane metal electrode layer is then placed on top of the insulating layer and the highly doped GaAs ohmic contact layer.

[0026] The groove-shaped current injection region is prepared using a wet etching process, and its sidewalls form an angle with the horizontal plane, creating a slope. The slope is primarily for metal coverage, and based on current data, the angle ranges from 45°.

[0027] The groove-shaped current injection region etches away all the undoped GaAs layer and part of the highly doped GaAs ohmic contact layer. The groove-shaped current injection region etches 100nm to 200nm of highly doped GaAs ohmic contact layer.

[0028] The undoped GaAs layer has a thickness of 400 nm. The highly doped GaAs ohmic contact layer has a thickness of 500 nm. The insulating layer is a SiO2 layer with a thickness of 400 nm. The insulating layer is grown using PECVD and the insulating layer in the current injection region is etched away. The substrate is made of GaAs. The N-plane metal is made of AuGeNi with a thickness of 500 nm. The N-plane confinement layer is made of Al. 70 Ga 30 As, with a thickness of 6000 nm. The N-plane waveguide layer is made of Al. 20 Ga 80 The As material has a thickness of 800 nm. The active layer is InGaAsP with a thickness of 7 nm. The P-plane waveguide layer is made of Al. 20 Ga 80 As, the thickness is 800nm. The P-side confinement layer is made of Al. 70 Ga 30 The As material is 4000 nm thick. The P-side metal is TiPtAu with a thickness of 600 nm. The width of the bottom of the current injection region is 200 μm.

[0029] By using the above parameters, the slow axis divergence angle is reduced to 8°, while the slow axis divergence angle of the ridge laser with the same epitaxial structure is 11°, thus significantly improving the beam quality of this application.

[0030] Example 2:

[0031] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the angle between the sidewall of the groove-shaped current injection region and the horizontal plane is 30°.

[0032] Example 3:

[0033] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the angle between the sidewall of the groove-shaped current injection region and the horizontal plane is 60°.

[0034] Example 4:

[0035] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the groove-shaped current injection region etches away all the undoped GaAs layer and the 100nm highly doped GaAs ohmic contact layer.

[0036] Example 5:

[0037] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the groove-shaped current injection region etches away all the undoped GaAs layer and the 200nm highly doped GaAs ohmic contact layer.

[0038] Example 6:

[0039] A low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect is disclosed, with the structure described in Example 1, except that the thickness of the undoped GaAs layer is 200 nm, and the thickness of the highly doped GaAs ohmic contact layer is 400 nm.

[0040] Example 7:

[0041] A low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect is disclosed, with the structure described in Example 1, except that the thickness of the undoped GaAs layer is 400 nm, and the thickness of the highly doped GaAs ohmic contact layer is 500 nm.

[0042] Example 8:

[0043] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the insulating layer material is a Si3N4 layer with a thickness of 300nm.

[0044] Example 9:

[0045] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the insulating layer material is a Si3N4 layer with a thickness of 500nm.

[0046] Example 10:

[0047] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the N-plane metal is made of TiPtAu.

[0048] Example 11:

[0049] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the width of the bottom of the current injection region is 190 μm.

[0050] Example 12:

[0051] A low divergence angle wide strip high-power semiconductor laser employing the anti-waveguide effect has the structure described in Example 1, except that the width of the bottom of the current injection region is 300 μm.

[0052] Finally, it should be noted that any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention. Although specific embodiments of this invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of this invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of this invention are still within the scope of protection of this invention.

Claims

1. A low-divergence-angle, wide-strip high-power semiconductor laser employing the anti-waveguide effect, characterized in that, From bottom to top, the layers are: an N-plane metal layer, a substrate, an N-type confinement layer, an N-type waveguide layer, an active layer, a P-type waveguide layer, a P-type confinement layer, a highly doped GaAs ohmic contact layer, an undoped GaAs layer, an insulating layer, and a P-plane metal layer. Above this is a current injection region, which is groove-shaped and formed by etching away all the undoped GaAs layer and part of the highly doped GaAs ohmic contact layer. The two sides of the groove-shaped current injection region are covered with an insulating layer. The insulating layer and the highly doped GaAs ohmic contact layer are covered with P-plane metal.

2. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The sidewall of the current injection region forms an angle with the horizontal plane.

3. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 2, characterized in that, The included angle ranges from 30° to 60°.

4. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The groove-shaped current injection region is used to etch a 100nm-200nm highly doped GaAs ohmic contact layer.

5. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The thickness of the undoped GaAs layer is 200–400 nm.

6. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The thickness of the highly doped GaAs ohmic contact layer is 400–500 nm.

7. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The insulating layer material is a SiO2 layer or a Si3N4 layer.

8. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The insulating layer material is grown using PECVD and the insulating layer in the current injection region is etched away.

9. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The thickness of the insulating layer material is 300–700 nm.

10. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 9, characterized in that, The thickness of the insulating layer is maintained between 300 nm and 500 nm.

11. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The substrate material includes any one of GaAs, SiC, SiN, GaN, and InP; the N-side metal material includes any one of AuGeNi and TiPtAu.

12. The low divergence angle wide-strip high-power semiconductor laser employing the anti-waveguide effect according to claim 1, characterized in that, The width of the bottom of the current injection region is 190μm to 300μm.

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