A semiconductor laser

Abstract

This application provides a semiconductor laser, comprising: a waveguide array composed of multiple sub-waveguides; an optical coupler disposed at one end of the waveguide array; an anti-reflection film disposed at the optical output end of the optical coupler; and a high-reflection film disposed at the other end of the waveguide array. This application achieves an increase in the optical output power of the semiconductor laser.

Description

Technical Field

[0001] This application relates to the field of semiconductors, and more specifically, to a semiconductor laser. Background Technology

[0002] Semiconductor lasers are lasers that use semiconductor materials as their working medium. They have many advantages, such as small size, high efficiency, long lifespan, and ease of integration, and are therefore widely used in imaging, communication, and machining. Due to the limitations of their physical structure, traditional semiconductor lasers cannot achieve high optical output power with a single tube. High power output can only be achieved through spatial beam combining methods of laser bars, such as direct fiber coupling, wavelength multiplexing, and polarization multiplexing.

[0003] However, for single-mode semiconductor lasers, direct fiber coupling generally results in significant losses. Furthermore, due to the single wavelength, spatial beam combining cannot be achieved through wavelength multiplexing. Additionally, the output light from lasers on the same bar typically exhibits the same polarization state; therefore, polarization combining offers very limited improvement to output power and introduces additional optical losses. Summary of the Invention

[0004] The purpose of this application is to provide a semiconductor laser to improve the optical output power of the semiconductor laser.

[0005] The first aspect of this application provides a semiconductor laser, comprising: a waveguide array composed of a plurality of sub-waveguides; an optical coupler disposed at one end of the waveguide array; an anti-reflection film disposed at the optical output end of the optical coupler; and a high-reflection film disposed at the other end of the waveguide array.

[0006] In one embodiment, the waveguide array includes: a first waveguide array, which is a ridge waveguide array, and one end of the first waveguide array is connected to the optical input terminal of the optical coupler; and a second waveguide array, which is also a ridge waveguide array, and is disposed at the other end of the first waveguide array.

[0007] In one embodiment, both the waveguide array and the optical coupler are formed on a semiconductor epitaxial layer; the semiconductor epitaxial layer comprises, from bottom to top, a substrate, a lower confinement layer, a quantum well, an upper confinement layer, and an ohmic contact layer.

[0008] In one embodiment, the thickness of the ohmic contact layer is zero in the region where the first waveguide array and the optical coupler are formed on the semiconductor epitaxial layer.

[0009] In one embodiment, the ridge height of the ridge waveguide array is less than or equal to the total thickness of the ohmic contact layer and the upper confinement layer.

[0010] In one embodiment, a groove is provided at the connection between the first waveguide array and the second waveguide array.

[0011] In one embodiment, the trench passes through the ohmic contact layer in the semiconductor epitaxial layer and extends to the upper confinement layer.

[0012] In one embodiment, the first waveguide array is composed of straight waveguides; the second waveguide array is composed of one or more of straight waveguides, curved waveguides, and tapered waveguides.

[0013] In one embodiment, the width of the optical coupler is greater than the total width of the waveguide array.

[0014] In one embodiment, the end of the second waveguide array connected to the first waveguide array has the same waveguide spacing and / or the same single waveguide width as the first waveguide array. Attached Figure Description

[0015] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the structure of a semiconductor laser according to an embodiment of this application;

[0017] Figure 2 This is a schematic diagram of the structure of a semiconductor laser according to an embodiment of this application;

[0018] Figure 3a This is a schematic diagram of the structure of a tapered waveguide according to an embodiment of this application;

[0019] Figure 3b This is a schematic diagram of the structure of a tapered waveguide according to an embodiment of this application;

[0020] Figure 3c This is a schematic diagram of the structure of a tapered waveguide according to an embodiment of this application;

[0021] Figure 4 This is a schematic diagram of the structure of a semiconductor laser according to an embodiment of this application;

[0022] Figure 5 This is a schematic diagram of the structure of a semiconductor epitaxial layer according to an embodiment of this application.

[0023] Figure label:

[0024] 100 - Semiconductor laser; 110 - Waveguide array; 111 - First waveguide array; 112 - Second waveguide array; 1121 - First sub-waveguide; 1122 - Second sub-waveguide; 1123 - Third sub-waveguide; 113 - Trench; 120 - Optical coupler; 130 - Anti-reflection coating; 140 - High-reflection coating; 150 - Semiconductor epitaxial layer; 151 - Substrate; 152 - Lower confinement layer; 153 - Quantum well; 154 - Upper confinement layer; 155 - Ohmic contact layer; 2 - Optical field convergence point. Detailed Implementation

[0025] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0026] In the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and do not indicate a sequence number, nor should they be construed as indicating or implying relative importance.

[0027] In the description of this application, terms such as "horizontal," "vertical," and "hanging" do not imply that the component is required to be absolutely horizontal or hanging, but rather that it may be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0028] In the description of this application, the terms "upper", "lower", "left", "right", "front", "back", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this application is usually placed in when in use. They are only for the convenience of describing this application and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0029] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0030] Please refer to Figure 1This is a schematic diagram of the structure of a semiconductor laser 100 according to an embodiment of this application. The semiconductor laser 100 includes: a waveguide array 110, an optical coupler 120, an anti-reflection film 130, and a high-reflection film 140. The waveguide array 110 is composed of multiple sub-waveguides. The optical coupler 120 is disposed at one end of the waveguide array 110. The width of the optical coupler 120 is greater than the total width of the waveguide array 110. In one embodiment, the width W1 of the optical coupler 120 can vary from 6 μm to 200 μm. In another embodiment, the width W1 of the optical coupler 120 can vary from 6 μm to 50 μm.

[0031] An anti-reflection film 130 is disposed at the optical output end of the optical coupler 120. In one embodiment, the reflectivity of the anti-reflection film 130 is less than 5%, and in another embodiment, the reflectivity of the anti-reflection film 130 is less than 2.5%. A high-reflection film 140 is disposed at the other end of the waveguide array 110. In one embodiment, the reflectivity of the high-reflection film 140 is not less than 80%, and in another embodiment, the reflectivity of the high-reflection film 140 is greater than 90%.

[0032] In one embodiment, the waveguide array 110 includes a first waveguide array 111 and a second waveguide array 112, wherein both the first waveguide array 111 and the second waveguide array 112 are ridge waveguide arrays. In one embodiment, the ridge waveguide can be realized by dry etching of P-type doped material or by wet etching of P-type doped material.

[0033] One end of the first waveguide array 111 is connected to the optical input terminal of the optical coupler 120, and the second waveguide array 112 is disposed at the other end of the first waveguide array 111. In one embodiment, the length L2 of the first waveguide array 111 is less than 500 μm, and in another embodiment, the length L2 of the first waveguide array 111 is less than 50 μm.

[0034] In one embodiment, the length of the first waveguide array 111 can be zero, and the second waveguide array 112 is disposed at the optical input end of the optical coupler 120.

[0035] In one embodiment, both the first waveguide array 111 and the second waveguide array 112 are composed of straight ridge waveguides. The waveguide spacing of the first waveguide array 111 and the second waveguide array 112 is the same, the width of a single waveguide is the same, and the ridge width W2 is 2μm to 10μm. In one embodiment, the ridge width W2 is 3μm to 6μm.

[0036] In one embodiment, the second waveguide array 112 has current injection to provide gain for the semiconductor laser 100, while the first waveguide array 111 and the optical coupler 120 have no current injection and are absorption regions.

[0037] In one embodiment, the optical coupler 120 can be an MMI (Multimode Interference) coupler. An MMI coupler utilizes the SIE (Self Imaging Effect) principle of light to achieve the function of beam splitting and combining optical power. For an MMI coupler, after the optical field from the ridge waveguide array input to the MMI coupler propagates a certain transmission distance S through the MMI coupler, multimode interference causes energy to concentrate, thus enabling the beam combining of multiple waveguide beams and coupling the energy together for output.

[0038] Based on the above principle, if the length L1 of the multimode waveguide of the MMI coupler is equal to the transmission distance S, the optical field after propagation through the MMI coupler will be combined into the fundamental transverse mode output, and coupling can be achieved with a single optical fiber. If L1 is slightly smaller than S, but L1 is large enough that the multimode interference effect is nearly complete, then the output port of the MMI coupler will have a wider optical field distribution than the fundamental transverse mode, thereby reducing the optical field energy density at the output end face. Due to the continued multimode superposition interference, the optical field energy at the output end face will be converged at a distance from the output end face without reducing the fiber coupling efficiency.

[0039] Therefore, by selecting an appropriate length L1 for the MMI coupler, it is possible to achieve beam combining of the optical field, reduce the optical energy density at the output end face, and maintain fiber coupling efficiency, thereby significantly improving the output power of the device. The optical transmission characteristics in a multimode waveguide can be obtained through guided-mode transmission analysis.

[0040]

[0041] Where L is the distance period of the self-image, λ is the wavelength, and W e n is the equivalent width of the fundamental mode in a multimode waveguide. r Given the equivalent refractive index, the width of the multimode waveguide is W. For waveguides with high refractive index differences, W... e ≈W; For waveguides with low refractive index differences, W e Slightly larger than W.

[0042] For a symmetrically designed single waveguide structure, where the central axis of the waveguide array 110 coincides with the central axis of the optical coupler 120, the distance from the optical input port of the optical coupler 120 to the first optical field convergence point 2 is L / 4. If the number of ridge waveguides in the symmetrically designed waveguide array 110 is N, then the distance from the optical input port of the optical coupler 120 to the first optical field convergence point 2 is L / 4N. Therefore, if the distance from the optical input port of the optical coupler 120 to the first optical field convergence point 2 is defined as L', then the length L1 of the optical coupler 120 is between 0.6×L' and L'. In one embodiment, the length L1 of the optical coupler 120 is between 0.7×L' and 0.95×L'. This allows the multimode interference effect of the optical coupler 120 to be nearly complete. The optical output port of the optical coupler 120 will have a wider optical field distribution than the fundamental transverse mode, thereby reducing the optical field energy density at the optical output end face. Due to the continued multimode superposition interference, the emitted optical field will achieve convergence of optical field energy at a distance from the optical output end face without reducing the fiber coupling efficiency, which greatly improves the optical output power of the semiconductor laser 100.

[0043] like Figure 2 The diagram shown is a schematic representation of a semiconductor laser 100 according to an embodiment of this application. The semiconductor laser 100 includes a waveguide array 110, an optical coupler 120, an anti-reflection coating 130, and a high-reflection coating 140. The waveguide array 110 includes a first waveguide array 111 and a second waveguide array 112, wherein the first waveguide array 111 is composed of straight waveguides, and the second waveguide array 112 is composed of straight waveguides and curved waveguides.

[0044] A high-reflectivity film 140 is disposed at one end of the second waveguide array 112, and the other end of the second waveguide array 112 is connected to one end of the first waveguide array 111. The end of the second waveguide array 112 connected to the first waveguide array 111 has equal waveguide spacing and / or equal single-waveguide width with the first waveguide array 111. The other end of the first waveguide array 111 is connected to the optical input end of the optical coupler 120, and an anti-reflectivity film 130 is disposed at the optical output end of the optical coupler 120.

[0045] In one embodiment, the second waveguide array 112 includes a first sub-waveguide 1121, a second sub-waveguide 1122, and a third sub-waveguide 1123. The first sub-waveguide 1121 and the third sub-waveguide 1123 are both S-shaped curved waveguides, while the second sub-waveguide 1122 is a straight waveguide. The waveguide width of the second sub-waveguide 1122 is equal to the waveguide width of the straight waveguides constituting the first waveguide array 111. The first sub-waveguide 1121 and the third sub-waveguide 1123 are symmetrically arranged about the second sub-waveguide 1122, such that the waveguide spacing at the end of the second waveguide array 112 coated with the high-reflectivity film 140 is greater than the waveguide spacing at the end connecting to the first waveguide array 111. This dispersed waveguide arrangement is beneficial for waveguide fabrication and heat dissipation. Simultaneously, to minimize losses caused by the curved waveguides, the bending angle of the first sub-waveguide 1121 and the third sub-waveguide 1123 at any point in the S-shaped segment is less than or equal to 15°. In one embodiment, the S-shaped curved waveguide includes, but is not limited to, double-circular arc type, rising arcsine type, and cosine function type.

[0046] In one embodiment, the sub-waveguides constituting the second waveguide array 112 can be outwardly expanded waveguide structures, that is, the waveguide width at one end of the sub-waveguide of the second waveguide array 112 coated with the high-reflectivity film 140 is greater than the waveguide width at the other end, thereby increasing the area of ​​the second waveguide array 112, allowing for a larger injection current, and thus improving the output power.

[0047] In one embodiment, the sub-waveguides of the second waveguide array 112 include, but are not limited to, tapered waveguides and their composite structures, and the boundary line of a single tapered waveguide can be a straight line (e.g., Figure 3a As shown), it can be a curve (such as...). Figure 3b As shown), it can also be a combination of straight lines with different angles of inclination (such as...). Figure 3c (As shown). In one embodiment, the individual waveguides constituting the second waveguide array 112 may be partially or entirely tapered waveguides. In one embodiment, the width of the end face of a single tapered waveguide near the high-reflectivity film 140 may range from 3 μm to 100 μm; in another embodiment, the width of the end face of a single tapered waveguide near the high-reflectivity film 140 may range from 6 μm to 15 μm.

[0048] In one embodiment, the first waveguide array 111 is composed of straight waveguides, and the second waveguide array 112 is composed of one or more of straight waveguides, curved waveguides, and tapered waveguides.

[0049] like Figure 4The diagram shown is a schematic representation of a semiconductor laser 100 according to an embodiment of this application. A trench 113 is provided at the connection between the first waveguide array 111 and the second waveguide array 112. The trench 113 is used to increase electrical isolation and further reduce current diffusion. In one embodiment, the width of the trench 113 ranges from 0.5 μm to 50 μm; in another embodiment, the width of the trench 113 ranges from 2 μm to 20 μm.

[0050] In one embodiment, the length of the first waveguide array 111 is zero, that is, the first waveguide array 111 does not exist in the waveguide array 110, then the trench 113 is disposed between the second waveguide array 112 and the optical input end of the optical coupler 120.

[0051] In one embodiment, the material system of the semiconductor laser 100 includes, but is not limited to, InP, GaAs, GaN, GaSb, etc.

[0052] like Figure 5 The diagram shown is a schematic representation of the structure of a semiconductor epitaxial layer 150 according to an embodiment of this application. Both the waveguide array 110 and the optocoupler 120 are formed on the semiconductor epitaxial layer 150. The semiconductor epitaxial layer 150, from bottom to top, includes: a substrate 151, a lower confinement layer 152, a quantum well 153, an upper confinement layer 154, and an ohmic contact layer 155. The waveguide array 110 is a ridge waveguide array, and the ridge height of the ridge waveguide array is less than or equal to the total thickness of the ohmic contact layer 155 and the upper confinement layer 154.

[0053] In one embodiment, the second waveguide array 112 has current injection to provide gain for the semiconductor laser 100, while the first waveguide array 111 and the optocoupler 120 have no current injection and are absorption regions. Within the region where the first waveguide array 111 and the optocoupler 120 are formed on the semiconductor epitaxial layer 150, the semiconductor epitaxial layer 150, from bottom to top, comprises only: a substrate 151, a lower confinement layer 152, a quantum well 153, and an upper confinement layer 154. In one embodiment, the highly p-type doped ohmic contact layer 155 in this region can be removed by dry etching or wet etching of the uppermost material of the semiconductor epitaxial layer 150, with an etching depth of 50 nm to 2 μm. In one embodiment, the etching depth is 100 nm to 600 nm.

[0054] In one embodiment, current is injected into the second waveguide array 112, the first waveguide array 111, and the optocoupler 120. In the region where the first waveguide array 111 and the optocoupler 120 are formed on the semiconductor epitaxial layer 150, the semiconductor epitaxial layer 150, from bottom to top, includes: a substrate 151, a lower confinement layer 152, a quantum well 153, an upper confinement layer 154, and an ohmic contact layer 155. Furthermore, a trench 113 is provided at the connection between the first waveguide array 111 and the second waveguide array 112. The highly conductive ohmic contact layer 155 at the trench 113 is etched, preventing the injected current in the region of the second waveguide array 112 from entering the region of the first waveguide array 111 and the optocoupler 120, thereby increasing the electrical isolation effect between the first waveguide array 111 and the second waveguide array 112. The injected current at the first waveguide array 111 and the optocoupler 120 is near the transparent current, resulting in lower optical loss or optical gain in this region.

[0055] In one embodiment, when current is injected into the region of the optocoupler 120, the etching depth of the optocoupler 120 does not exceed the total thickness of the ohmic contact layer 155 and the upper confinement layer 154, that is, the optocoupler 120 is not etched to the quantum well 153.

[0056] In one embodiment, when there is no current injection in the region of the optocoupler 120, the optocoupler 120 can be etched to the upper confinement layer 154, the quantum well 153, or the lower confinement layer 152.

[0057] In one embodiment, the trench 113 passes through the ohmic contact layer 155 in the semiconductor epitaxial layer 150 and extends to the upper confinement layer 154. In one embodiment, the trench 113 is etched downward from the ohmic contact layer 155, and the etching depth can range from greater than 200 nm to a depth above the quantum well 153. The width of the trench 113 along the direction of the waveguide array 110 is 0.5 μm to 50 μm. In one embodiment, the width of the trench 113 along the direction of the waveguide array 110 is 2 μm to 20 μm.

[0058] The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A semiconductor laser, characterized in that, include: A waveguide array, wherein the waveguide array is composed of multiple sub-waveguides; An optical coupler is disposed at one end of the waveguide array; An anti-reflection film is disposed at the optical output end of the optical coupler; A high-reflectivity film is disposed at the other end of the waveguide array; The waveguide array includes a first waveguide array and a second waveguide array; wherein the second waveguide array includes a first sub-waveguide, a second sub-waveguide and a third sub-waveguide, the first sub-waveguide and the third sub-waveguide are symmetrically arranged about the second sub-waveguide, the first sub-waveguide and the third sub-waveguide are S-shaped curved waveguides, and the bending angle of the S-shaped curved waveguide at any point is less than or equal to 15 degrees; The waveguide array and the optical coupler are both formed on a semiconductor epitaxial layer; the semiconductor epitaxial layer includes an upper confinement layer and an ohmic contact layer; a trench is provided at the connection between the first waveguide array and the second waveguide array; the trench passes through the ohmic contact layer in the semiconductor epitaxial layer and extends to the upper confinement layer; The optical coupler is a multimode interference coupler, the central axis of the optical coupler coincides with the central axis of the waveguide array, the length of the optical coupler ranges from 0.7L' to 0.95L', where L' is the distance from the optical input port of the optical coupler to the first optical field convergence point, and L' is L / 4, where L is the distance period of the self-image. The distance period of the self-image is determined by the optical transmission characteristics of the multimode interference coupler: ， Where L is the distance period of the self-image, λ is the wavelength, and W e n is the equivalent width of the fundamental mode in a multimode waveguide. r Given the equivalent refractive index, the width of the multimode waveguide is W. For waveguides with high refractive index differences, W... e ≈W; for waveguides with low refractive index differences, W e Slightly larger than W.

2. The semiconductor laser according to claim 1, characterized in that, The first waveguide array is a ridge waveguide array, and one end of the first waveguide array is connected to the optical input end of the optical coupler; The second waveguide array is a ridge waveguide array, and the second waveguide array is located at the other end of the first waveguide array.

3. The semiconductor laser according to claim 1, characterized in that, The semiconductor epitaxial layer comprises, from bottom to top, a substrate, a lower confinement layer, a quantum well, an upper confinement layer, and an ohmic contact layer.

4. The semiconductor laser according to claim 3, characterized in that, In the region where the first waveguide array and the optical coupler are formed on the semiconductor epitaxial layer, the thickness of the ohmic contact layer is zero.

5. The semiconductor laser according to claim 2, characterized in that, The ridge height of the ridge waveguide array is less than or equal to the total thickness of the ohmic contact layer and the upper confinement layer.

6. The semiconductor laser according to claim 2, characterized in that, The first waveguide array is composed of straight waveguides; the second waveguide array is composed of at least one of straight waveguides, curved waveguides, and tapered waveguides.

7. The semiconductor laser according to claim 1, characterized in that, The width of the optical coupler is greater than the total width of the waveguide array.

8. The semiconductor laser according to claim 2, characterized in that, The second waveguide array has one end connected to the first waveguide array and has the same waveguide spacing and / or the same single waveguide width as the first waveguide array.

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