Narrow-divergence-angle semiconductor laser

Abstract

The invention provides a narrow-divergence-angle semiconductor laser, which comprises an input ridge-shaped waveguide region, a phase locking region and a near-field intensity modulation region which are obtained by etching an active epitaxial structure and are sequentially connected along a light emitting direction, and is characterized in that the input ridge-shaped waveguide region comprises a first ridge-shaped waveguide array which is laterally and periodically distributed; the first ridge waveguide array comprises a plurality of first ridge waveguides; the phase-locked region comprises a first wide-region waveguide and a second ridge-shaped waveguide array which is periodically distributed in the lateral direction; the second ridge-shaped waveguide array comprises a plurality of second ridge-shaped waveguides; the near-field intensity modulation area comprises a second wide-area waveguide.

Description

Technical Field

[0001] This invention relates to the field of semiconductor laser technology, and more particularly to a narrow divergence angle semiconductor laser. Background Technology

[0002] Semiconductor lasers are widely used in industrial processing, medical applications, communications, and lidar due to their advantages such as small size, high efficiency, and strong wavelength tunability. However, traditional semiconductor lasers often face the problem of beam quality degradation at high power output, especially with a large lateral far-field divergence angle, leading to energy dispersion and limiting their application in precision machining, long-distance detection, and other scenarios with high beam quality requirements. To improve beam quality, researchers have proposed various technical solutions, among which waveguide array structures have attracted much attention due to their ability to effectively increase output power. However, while achieving high power output, waveguide array structures typically tend to lasing higher-order supermodes, resulting in a double-lobe or multi-lobe structure in the far-field intensity distribution, which seriously affects the practical application performance of the laser.

[0003] Existing phase-locked loop (PLL) techniques, such as evanescent wave coupling or leaky wave coupling, can achieve mode selection and beam shaping through specific waveguide arrangements and phase control regions. However, they are still not ideal in terms of fabrication difficulty, sensitivity to parameter errors, and energy concentration in the central main lobe. Therefore, how to provide a semiconductor laser that can achieve narrow divergence angle, high beam quality, fabrication robustness, and high power output capability has become an urgent problem to be solved. Summary of the Invention

[0004] In view of the above, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a narrow divergence angle semiconductor laser, the technical solution of which is as follows:

[0005] According to an embodiment of the present invention, a narrow divergence angle semiconductor laser is provided, comprising an input ridge waveguide region, a phase-locked region, and a near-field intensity modulation region sequentially connected along the light emission direction, etched on an active epitaxial structure, wherein: the input ridge waveguide region comprises a first ridge waveguide array with laterally periodic distribution, the first ridge waveguide array comprising a plurality of first ridge waveguides; the phase-locked region comprises a first wide-area waveguide and a second ridge waveguide array with laterally periodic distribution, the second ridge waveguide array comprising a plurality of second ridge waveguides; and the near-field intensity modulation region comprises a second wide-area waveguide.

[0006] According to an embodiment of the present invention, the first ridge waveguide array is arranged symmetrically about the longitudinal centerline of the laser output cavity surface.

[0007] According to an embodiment of the present invention, the waveguide widths of the first ridge waveguide and the second ridge waveguide are the same; the spacing between the central axes of adjacent first ridge waveguides and the spacing between the central axes of adjacent second ridge waveguides are the same.

[0008] According to an embodiment of the present invention, a plurality of second ridge waveguides are staggered with a plurality of first ridge waveguides, and the stagger distance is half the distance between the central axes of adjacent first ridge waveguides or second ridge waveguides.

[0009] According to an embodiment of the present invention, the first ridge waveguide array includes at least three first ridge waveguides; the second ridge waveguide array includes at least three second ridge waveguides.

[0010] According to an embodiment of the present invention, the waveguide widths of the first ridge waveguide and the second ridge waveguide are smaller than the first-order transverse mode cutoff width, so as to ensure that a single ridge waveguide only supports single transverse mode operation.

[0011] According to an embodiment of the present invention, the lateral width of the first wide-area waveguide is D1, and the longitudinal length of the first wide-area waveguide along the light-emitting direction is L1, then:

[0012] D1≥d(N-1)+2w;

[0013] L1=M*Z t / 2;

[0014] Where d represents the spacing between the central axes of adjacent first ridge waveguides, w represents the waveguide width of the first ridge waveguide, N represents the number of first ridge waveguides, M is a positive odd number, and Z t This represents the transmission distance at which the optical field between the first ridge waveguides in the first ridge waveguide array achieves self-imaging of the array's optical field through diffraction coupling in the phase-locked region.

[0015] According to an embodiment of the present invention, the lateral width of the second wide-area waveguide is D2, then:

[0016] D2≥d(N-1)+2w;

[0017] Where d represents the spacing between the central axes of adjacent second ridge waveguides, w represents the waveguide width of the second ridge waveguide, N represents the number of second ridge waveguides, and L2, the longitudinal length of the second wide-area waveguide along the light output direction, is the length corresponding to the minimum non-uniformity of the cross-sectional field strength distribution in the light transmission direction.

[0018] According to an embodiment of the present invention, the active epitaxial structure includes a substrate layer and an active layer. The substrate layer is made of GaAs, InP, or GaSb. The active layer has a single quantum well structure, a multiple quantum well structure, a quantum dot structure, or a superlattice structure.

[0019] According to an embodiment of the present invention, the first ridge waveguide and the second ridge waveguide are of the type of rectangular waveguide or tapered waveguide. Attached Figure Description

[0020] The objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0021] Figure 1 This is a three-dimensional structural diagram of a narrow divergence angle semiconductor laser according to an embodiment of the present invention.

[0022] Figure 2 This is a schematic diagram of the top structure of a narrow divergence angle semiconductor laser according to an embodiment of the present invention.

[0023] Figure 3 This is a schematic diagram comparing the cavity surface optical field distribution of a narrow divergence angle semiconductor laser with different lengths of the near-field intensity modulation region according to an embodiment of the present invention.

[0024] Figure 4 This is a schematic diagram showing the lateral far-field comparison of a narrow divergence angle semiconductor laser conductor laser with and without a near-field intensity modulation region, according to an embodiment of the present invention. Detailed Implementation

[0025] This invention provides a narrow divergence angle semiconductor laser, comprising an input ridge waveguide region, a phase-locked region, and a near-field intensity modulation region sequentially connected along the light output direction, etched on an active epitaxial structure. These can sequentially achieve in-phase mode selection and far-field sidelobe suppression, thereby obtaining a narrow single-lobe lateral far field. Under the premise of ensuring high output power, the lateral far field characteristics can be effectively improved.

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0027] In this embodiment of the invention, a narrow divergence angle semiconductor laser is provided, combined with Figure 1 and Figure 2 As shown, the semiconductor laser includes an input ridge waveguide region 1, a phase-locked region 2, and a near-field intensity modulation region 3, which are sequentially connected along the light emission direction and etched on an active epitaxial structure 100. The input ridge waveguide region 1 includes a laterally periodically distributed first ridge waveguide array, which comprises multiple first ridge waveguides a; the phase-locked region 2 includes a first wide-area waveguide 21 and a laterally periodically distributed second ridge waveguide array, which comprises multiple second ridge waveguides b; the near-field intensity modulation region includes a second wide-area waveguide 31. "Laterally" here refers to the direction perpendicular to the light emission direction.

[0028] According to an embodiment of the present invention, the first ridge waveguide array is arranged symmetrically about the longitudinal centerline of the laser output cavity surface.

[0029] According to an embodiment of the present invention, the waveguide widths of the first ridge waveguide and the second ridge waveguide are the same, such as... Figure 2 As shown, the waveguide widths of both the first and second ridge waveguides are w; the waveguide width w is less than the first-order transverse mode cutoff width. For example, when the operating wavelength is 2μm and the etching depth is 1.8μm, w can be set to 5.5μm to ensure that a single ridge waveguide only supports single-transverse mode operation. The spacing between the central axes of adjacent first ridge waveguides and adjacent second ridge waveguides is the same, both being d. For example, if seven first ridge waveguides are set and d is set to 22μm, the in-phase mode will have seven peaks in the lateral far field after phase locking. The far-field pattern can be changed by adjusting the value of d. The duty cycle f=w / d of the ridge waveguides in the first and second ridge waveguide arrays can be selected according to the actual situation, balancing the far-field distribution and mode resolution. The embodiments of the present invention do not limit this.

[0030] According to an embodiment of the present invention, in the first ridge waveguide array and the second ridge waveguide array, there is a groove between adjacent ridge waveguides, and the width of the groove is w. T The injection wavelength can be much larger than the laser's lasing wavelength, which is beneficial for heat dissipation at high injection levels.

[0031] According to an embodiment of the present invention, a plurality of second ridge waveguides are staggered with a plurality of first ridge waveguides, and the stagger distance is half the distance between the central axes of adjacent first ridge waveguides or second ridge waveguides, that is, the stagger distance is d / 2.

[0032] According to an embodiment of the present invention, the first ridge waveguide array includes at least three first ridge waveguides; the second ridge waveguide array includes at least three second ridge waveguides, such as... Figure 1 and Figure 2 The diagram shows seven first ridge waveguides (a) and seven second ridge waveguides (b).

[0033] According to an embodiment of the present invention, the lateral width of the first wide-area waveguide 21 is D1, and the longitudinal length of the first wide-area waveguide 21 along the light-emitting direction is L1, then:

[0034] D1≥d(N-1)+2w;

[0035] L1 = M / 2 × Z t ;

[0036] Where d represents the spacing between the central axes of adjacent first ridge waveguides, w represents the waveguide width of the first ridge waveguide, N represents the number of first ridge waveguides, M is a positive odd number, such as M = 1, 3, 5, 7, 9, etc., Z tThis represents the transmission distance for self-imaging of the array's optical field between the first ridge waveguides in the first ridge waveguide array, achieved through diffraction coupling in the phase-locked region. The first wide-area waveguide 21 serves as the phase-locked cavity of the phase-locked region 2, where the in-phase mode is located at M / 2×Z of the phase-locked cavity. t The bright region of the mode appears at a offset of d / 2 from the first ridge waveguide array. The distribution of the remaining supermode fields is significantly different from that of the in-phase mode. Therefore, the longitudinal length L1 of the first wide-area waveguide 21 along the light output direction is set to M / 2×Z. t Furthermore, the lateral position of the second ridge waveguide array is offset by d / 2 compared to the first ridge waveguide array. Therefore, the coupling efficiency of the in-phase mode from the first wide-area waveguide 21 to the second ridge waveguide array is significantly higher than that of other supermodes, thereby enhancing the mode competition capability of the in-phase mode.

[0037] The lateral width of the near-field intensity modulation region needs to be greater than the output aperture of the second ridge waveguide array. Let the lateral width of the second wide-area waveguide 31 be D2, then:

[0038] D2≥d(N-1)+2w;

[0039] Where d represents the spacing between the central axes of adjacent second ridge waveguides, w represents the waveguide width of the second ridge waveguide, N represents the number of second ridge waveguides, and L2, the longitudinal length of the second wide-area waveguide 31 along the light-emitting direction, is the length corresponding to the minimum non-uniformity of the cross-sectional field intensity distribution in the light transmission direction. To achieve high energy density single-lobe narrow divergence angle far-field output, the near field needs to have a uniform distribution of amplitude and phase. The phase-locked loop structure achieves in-phase mode selection, but the inherent spacing of the ridge waveguide array causes the optical field amplitude distribution to be non-uniform. Therefore, the longitudinal length L2 of the near-field intensity modulation region along the light-emitting direction is set according to the length corresponding to the minimum non-uniformity of the cross-sectional field intensity distribution in the light transmission direction. Figure 3 schematically shown Figure 2 The diagram shows a comparison of the cavity surface optical field distribution as the longitudinal length L2 of the near-field intensity modulation region of the narrow divergence angle semiconductor laser increases from 0 to 300 μm. It is evident that the near-field inhomogeneity decreases. Specifically, the values ​​described above in this embodiment represent the near-field intensity modulation region length of the preferred embodiment of the present invention, but are not limited to these values. Figure 4 schematically shown Figure 2 The diagram shows the lateral far-field comparison of a narrow divergence angle semiconductor laser with and without a near-field intensity modulation region. It can be seen that the sidelobe intensity of the lateral far-field is significantly reduced after the near-field intensity modulation region is added, and the far-field divergence angle of the central main lobe is close to the diffraction limit, reaching about 1 degree.

[0040] According to an embodiment of the present invention, the active epitaxial structure 100 includes a substrate layer and an active layer. The substrate layer is made of GaAs, InP or GaSb, or other III-V compounds. The active layer has a single quantum well structure, a multiple quantum well structure, a quantum dot structure or a superlattice structure.

[0041] According to an embodiment of the present invention, the first ridge waveguide and the second ridge waveguide are of the type of rectangular waveguide or tapered waveguide.

[0042] According to an embodiment of the present invention, the input ridge waveguide region 1, the phase-locked region 2, and the near-field intensity modulation region 3 can all be obtained by etching on the top of the active epitaxial structure. The etching depth can be selected from the top of the active epitaxial structure to the top of the substrate, that is, the input ridge waveguide region 1, the phase-locked region 2, and the near-field intensity modulation region 3 are obtained by etching the active layer in the active epitaxial structure.

[0043] The narrow divergence angle semiconductor laser of the present invention has at least the following beneficial effects:

[0044] (1) The phase-locked region structure can effectively suppress the high-order supermode lasing and increase the mode competition capability of the in-phase mode by transmitting the optical field through the array waveguide self-reproduction effect.

[0045] (2) The near-field intensity modulation region structure can realize the transition from non-uniform near-field distribution to more uniform distribution after phase locking, thereby achieving sidelobe suppression, increasing the energy concentration of the central main lobe, realizing single-lobe far-field lasing, and obtaining a lateral far-field divergence angle close to the diffraction limit.

[0046] (3) The diffraction coupling scheme is adopted. Compared with the evanescent wave coupling and leakage wave coupling schemes, the edge spacing of adjacent ridge waveguides in the ridge waveguide array is more flexible and can promote heat dissipation of the device, which is conducive to achieving high power output.

[0047] (4) It adopts various common epitaxial growth, thin film deposition, photolithography and etching processes, without the need for complex processes such as secondary epitaxy, is compatible with conventional manufacturing processes, and is not sensitive to structural geometric parameters and process errors, thus having manufacturing process robustness.

[0048] In summary, the narrow divergence angle semiconductor laser provided by this invention utilizes the self-imaging effect of the phase-locked region structure through the ridge waveguide array to effectively suppress high-order supermode lasing and increase the mode competition capability of in-phase modes. This structure exhibits high mode resolution and mode stability. The near-field intensity modulation region structure enables a transition from a non-uniform near-field distribution to a more uniform distribution after phase-locking, thereby achieving sidelobe suppression, increasing the energy concentration of the central main lobe, and realizing single-lobe far-field lasing. The resulting lateral far-field divergence angle approaches the diffraction limit. Furthermore, this invention employs a diffraction coupling scheme. Compared to evanescent wave coupling and leakage wave coupling schemes, the width of the grooves between adjacent ridge waveguides in the ridge waveguide array is more flexible and allows for wider settings, promoting heat dissipation and facilitating high-power output. In terms of fabrication, it utilizes common epitaxial growth, thin film deposition, photolithography, and etching processes, eliminating the need for complex processes such as secondary epitaxy. It is compatible with conventional manufacturing processes and is insensitive to structural geometric parameters and process errors, exhibiting robust manufacturing performance.

[0049] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. It should be noted that implementations not illustrated or described in the drawings or the main text of the specification are forms known to those skilled in the art and have not been described in detail. It should be understood that the above are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1.A narrow-divergence semiconductor laser, comprising an input ridge waveguide region, a phase-locked region and a near-field intensity modulation region, which are sequentially connected along the light emission direction and are etched on an active epitaxial structure, wherein: the input ridge waveguide region comprises a first array of periodically distributed ridge waveguides, the first array of ridge waveguides comprises a plurality of first ridge waveguides; the phase-locked region comprises a first wide waveguide and a second array of periodically distributed ridge waveguides, the second array of ridge waveguides comprises a plurality of second ridge waveguides; and the near-field intensity modulation region comprises a second wide waveguide. 2.The narrow-divergence semiconductor laser of claim 1, wherein the first array of ridge waveguides is symmetrically arranged about a longitudinal center line of a light emission cavity surface of the laser. 3.The narrow-divergence semiconductor laser of claim 1, wherein the first ridge waveguides and the second ridge waveguides have the same waveguide width, and the distance between the center axes of adjacent first ridge waveguides is the same as the distance between the center axes of adjacent second ridge waveguides. 4.The narrow-divergence semiconductor laser of claim 1, wherein the plurality of second ridge waveguides are staggered with the plurality of first ridge waveguides, and the staggered distance is half of the distance between the center axes of adjacent first ridge waveguides or second ridge waveguides. 5.The narrow-divergence semiconductor laser of claim 1, wherein the first array of ridge waveguides comprises at least three first ridge waveguides, and the second array of ridge waveguides comprises at least three second ridge waveguides. 6.The narrow-divergence semiconductor laser of claim 1, wherein the waveguide width of the first ridge waveguides and the second ridge waveguides is less than the first-order transverse mode cutoff width, so as to ensure that a single ridge waveguide only supports single transverse mode operation. 7.The narrow-divergence semiconductor laser of claim 1, wherein the first wide waveguide has a lateral width of D1, and a longitudinal length L1 along the light emission direction, and D1≥d(N-1)+2w. 8.The narrow-divergence semiconductor laser of claim 1, wherein the second wide waveguide has a lateral width of D2, and D2≥d(N-1)+2w. d represents the distance between the center axes of adjacent second ridge waveguides, w represents the waveguide width of the second ridge waveguides, N represents the number of second ridge waveguides, and L2 is the length corresponding to the minimum non-uniformity of the cross-sectional field intensity distribution in the light transmission direction. L1 = M*Z t / 2; wherein, d represents the spacing between the center axes of adjacent first ridge waveguides, w represents the waveguide width of the first ridge waveguides, N represents the number of the first ridge waveguides, M is a positive odd number, Z t represents the transmission distance of the array optical field to achieve self-imaging by the diffractive coupling of the optical field through the phase-locking region between the first ridge waveguides in the first ridge waveguide array. 9.The narrow-divergence semiconductor laser of claim 1, wherein the active epitaxial structure comprises a substrate layer and an active layer, the substrate layer is made of GaAs, InP or GaSb, and the active layer has a single quantum well structure, a multi-quantum well structure, a quantum dot structure or a superlattice structure. 10.The narrow-divergence semiconductor laser of claim 1, wherein the first ridge waveguides and the second ridge waveguides are rectangular waveguides or tapered waveguides. wherein ​ ​ ​

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