Waveguide structure of semiconductor laser

Abstract

This application discloses a waveguide structure for a semiconductor laser, relating to the field of semiconductor manufacturing technology. The waveguide structure of the semiconductor laser of this application includes a substrate, a lower confinement layer, a quantum well, an upper confinement layer, and a ridge forming layer. The lower confinement layer is disposed on the substrate; the quantum well is disposed on the lower confinement layer; the upper confinement layer is disposed on the quantum well; and the ridge forming layer is disposed on the upper confinement layer. The ridge forming layer includes etched trenches and ridge waveguides; wherein the top width of the etched trenches is 0.5-5 μm. Therefore, this application achieves coupling of higher-order modes by reducing the width of the etched trenches, increasing the loss of higher-order modes, thereby suppressing the lasing of higher-order modes and ensuring the stability of the fundamental mode lasing.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and more specifically, to a waveguide structure for a semiconductor laser. Background Technology

[0002] Semiconductor lasers are a widely used type of laser emitting device. Lasers are classified into single-mode and multi-mode based on their transverse mode emission. Suppressing the emission of higher-order modes is crucial for achieving kink-free high-power output in single-mode devices. Summary of the Invention

[0003] The purpose of this application is to provide a waveguide structure for a semiconductor laser that enables coupling of higher-order modes, increases the loss of higher-order modes, thereby suppressing lasing and ensuring the stability of fundamental mode lasing.

[0004] The embodiment of the present application is implemented as follows:

[0005] A waveguide structure for a semiconductor laser includes a substrate, a lower confinement layer, a quantum well, an upper confinement layer, and a ridge forming layer. The lower confinement layer is disposed on the substrate; the quantum well is disposed on the lower confinement layer; the upper confinement layer is disposed on the quantum well; and the ridge forming layer is disposed on the upper confinement layer. The ridge forming layer includes a layer body, an etched trench, and a ridge waveguide.

[0006] In one embodiment, the bottom width of the etched trench is 0.5-5 μm.

[0007] In one embodiment, the top width of the etching trench is greater than the bottom width of the etching trench, and the top width of the etching trench is 0.5-8μm.

[0008] In one embodiment, the substrate is made of a heavily doped N-type material, and the ridge forming layer is made of a P-type material.

[0009] In one embodiment, the lower confinement layer includes a first lower confinement layer and a second lower confinement layer, wherein the first lower confinement layer is disposed on the substrate; and the second lower confinement layer is sandwiched between the first lower confinement layer and the quantum well. The first lower confinement layer is made of a moderately doped N-type material, and the second lower confinement layer is made of an undoped semiconductor material.

[0010] In one embodiment, the upper confinement layer includes a first upper confinement layer and a second upper confinement layer, wherein the first upper confinement layer is disposed on the quantum well; the second upper confinement layer is sandwiched between the first upper confinement layer and the ridge forming layer; wherein the first upper confinement layer is made of an undoped semiconductor material, and the second upper confinement layer is made of a moderately doped P-type material.

[0011] In one embodiment, the etching trenches are provided in multiple ways, and the etching trenches are rectangular trenches; wherein, the ridge waveguide is sandwiched between two adjacent etching trenches, and the cross-section of the ridge waveguide along the thickness direction is rectangular.

[0012] In one embodiment, a light-absorbing element is provided on the inner bottom surface of the etched trench.

[0013] In one embodiment, a gap is left between the light absorber and the ridge waveguide.

[0014] In one embodiment, the size of the interval is 0.5-5 μm.

[0015] In one embodiment, the width of the light-absorbing element is less than or equal to the width of the bottom surface of the etched trench.

[0016] In one embodiment, the thickness of the light-absorbing element is less than or equal to the depth of the etched trench.

[0017] In one embodiment, the depth of the etched trench is 0.5-2 μm, and the thickness of the light-absorbing element is 0.05-1 μm.

[0018] In one embodiment, the depth of the etched trench is 0.5-1 μm, and the thickness of the light-absorbing element is 0.05-0.5 μm.

[0019] The advantages of this application compared to the prior art are:

[0020] This application achieves coupling of higher-order modes by reducing the width of the etching trenches, thereby increasing the loss of higher-order modes, suppressing the lasing of higher-order modes, and ensuring the stability of the fundamental mode lasing.

[0021] This application provides a light-absorbing element on the inner bottom surface of the etched trench. The light-absorbing element can serve as a loss layer for absorbing light, thereby increasing the loss of higher-order modes and suppressing the lasing of higher-order modes. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments 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.

[0023] Figure 1 This is a schematic diagram of the waveguide structure of a semiconductor laser according to an embodiment of this application;

[0024] Figure 2This is a schematic diagram of the waveguide structure of a semiconductor laser according to an embodiment of this application;

[0025] Figure 3 This is a schematic diagram of the waveguide structure of a semiconductor laser according to an embodiment of this application;

[0026] Figure 4 This is a schematic diagram of the optical field distribution of the fundamental mode of a waveguide structure of a semiconductor laser, as shown in an embodiment of this application.

[0027] Figure 5 This is a schematic diagram of the optical field distribution of a first-order mode of a waveguide structure of a semiconductor laser, as shown in an embodiment of this application.

[0028] Figure 6 This is a schematic diagram of the waveguide structure of a semiconductor laser according to an embodiment of this application.

[0029] Icons: 100 - Waveguide structure of semiconductor laser; 110 - Substrate; 120 - Lower confinement layer; 121 - First lower confinement layer; 122 - Second lower confinement layer; 130 - Quantum well; 140 - Upper confinement layer; 141 - First upper confinement layer; 142 - Second upper confinement layer; 150 - Ridge forming layer; 151 - Etched trench; 152 - Ridge waveguide; 153 - Layer body; 160 - Optical absorber; 161 - Spacing; 200 - Contour line of fundamental mode optical field; 300 - Contour line of first-order mode optical field. Detailed Implementation

[0030] The terms “first,” “second,” “third,” etc., are used only for distinguishing descriptions and do not indicate a sequence number, nor should they be interpreted as indicating or implying relative importance.

[0031] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can 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.

[0032] In the description of this application, it should be noted that the terms "inner", "outer", "left", "right", "upper", "lower", 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 commonly used when the product of this application is in use. They are only for the convenience of describing this application and simplifying the description, 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.

[0033] In the description of this application, unless otherwise expressly specified and limited, the terms “set up,” “install,” “connect,” and “link” shall be interpreted broadly, for example, as a fixed connection, a detachable connection, or an integral connection; as a mechanical connection or an electrical connection; as a direct connection or an indirect connection through an intermediate medium; or as a connection within two components.

[0034] The technical solution of this application will now be clearly and completely described with reference to the accompanying drawings.

[0035] Please refer to Figure 1 This is a schematic diagram of the waveguide structure 100 of a semiconductor laser according to an embodiment of this application. The waveguide structure 100 of a semiconductor laser includes a substrate 110, a lower confinement layer 120, a quantum well 130, an upper confinement layer 140, and a ridge forming layer 150 epitaxially grown from bottom to top. The lower confinement layer 120 is disposed on the substrate 110; the quantum well 130 is disposed on the lower confinement layer 120; the upper confinement layer 140 is disposed on the quantum well 130; and the ridge forming layer 150 is disposed on the upper confinement layer 140. The substrate 110 is made of heavily doped N-type material, and the ridge forming layer 150 is made of heavily doped P-type material. The quantum well 130 is used to confine electrons, and the upper confinement layer 140 and the lower confinement layer 120 are used to confine the light field.

[0036] Please refer to Figure 2 This is a schematic diagram of the waveguide structure 100 of a semiconductor laser according to an embodiment of this application. The waveguide structure 100 of the semiconductor laser has the following dimensions: W1—represents the top width of the etching trench 151; W2—represents the bottom width of the etching trench 151, i.e., the inner bottom surface width of the etching trench 151; D1—represents the trench depth of the etching trench 151; T1—represents the thickness of the layer body 153; W3—represents the width of the ridge waveguide 152. The trench width of the etching trench 151 includes the top width W1 and the bottom width W2 of the etching trench 151.

[0037] The ridge-forming layer 150 includes a layer body 153, etched trenches 151, and a ridge waveguide 152. Multiple etched trenches 151 are provided, and each etched trench 151 is a rectangular trench. The ridge waveguide 152 is sandwiched between two adjacent etched trenches 151, and the cross-section of the ridge waveguide 152 along the thickness direction is rectangular. In other embodiments, the etched trenches 151 can be trapezoidal or other shapes, and correspondingly, the cross-section of the ridge waveguide 152 along the thickness direction is trapezoidal.

[0038] In this embodiment, two etching trenches 151 are etched on the layer body 153, and a ridge waveguide 152 is formed between the two etching trenches 151. Therefore, the ridge forming layer 150 structure from left to right is the layer body 153, the etching trenches 151, the ridge waveguide 152, the etching trenches 151, and the layer body 153.

[0039] In this embodiment, the trench depth D1 of the etched trench 151 is equal to the thickness T1 of the layer body 153 and also equal to the thickness of the ridge waveguide 152. The top width W1 of the etched trench 151 is equal to the bottom width W2 of the etched trench 151. Both the top width W1 and the bottom width W2 of the etched trench 151 are 0.5-5 μm. If the bottom width W2 of the etched trench 151 is less than 0.5 μm, not only is the processing more difficult, but the light wavelength will also leak, and the excessively narrow etched trench 151 cannot confine the optical field mode. If the bottom width W2 of the etched trench 151 is greater than 5 μm, higher-order modes cannot couple to the upper confinement layer 140 due to the mode field distribution size limitation, mainly in the layer body 153, thus failing to suppress higher-order modes. Therefore, according to optical mode calculation simulation, a bottom width W2 of 0.5-5 μm for the etched trench 151 is a more suitable range.

[0040] In one embodiment, the top width W1 of the etching trench 151 is greater than the bottom width W2 of the etching trench 151, the top width W1 of the etching trench 151 is 0.5-8μm, and the bottom width W1 of the etching trench 151 is 0.5-5μm.

[0041] In one embodiment, the width of the ridge waveguide 152 can be designed according to the required optical output power; for example, the width W3 of the ridge waveguide 152 can be 3-10 μm.

[0042] Higher-order modes couple to the upper confinement layer 140 or the ridge forming layer 150 only occur when the width of the etching trench 151 is sufficiently small. Therefore, this embodiment reduces the width of the etching trench 151 to couple higher-order modes to the heavily doped p-type material of the ridge forming layer 150, thereby increasing the loss of higher-order modes, suppressing lasing of higher-order modes, increasing their lasing threshold, and indirectly increasing the stability of the fundamental mode lasing. In other words, this embodiment achieves stable operation of the fundamental transverse mode at high power by introducing greater loss to higher-order modes through a horizontal mode coupling method, thereby improving the kink-free power of the semiconductor laser output.

[0043] In one embodiment, a semiconductor laser with a top width of 0.5-5 μm for etching trench 151 has greater losses in higher-order modes compared to a semiconductor laser with a top width of 8 μm or 20 μm for etching trench 151.

[0044] Please refer to Figure 3 This is a schematic diagram of the waveguide structure 100 of a semiconductor laser according to an embodiment of this application. The lower confinement layer 120 includes a first lower confinement layer 121 and a second lower confinement layer 122. The first lower confinement layer 121 is disposed on the substrate 110; the second lower confinement layer 122 is sandwiched between the first lower confinement layer 121 and the quantum well 130. The first lower confinement layer 121 is made of a moderately doped N-type material, and the second lower confinement layer 122 is made of an undoped semiconductor material, thereby allowing the refractive index of the lower confinement layer 120 to gradually change.

[0045] The upper confinement layer 140 includes a first upper confinement layer 141 and a second upper confinement layer 142. The first upper confinement layer 141 is disposed on the quantum well 130; the second upper confinement layer 142 is sandwiched between the first upper confinement layer 141 and the ridge forming layer 150. The first upper confinement layer 141 is made of an undoped semiconductor material, and the second upper confinement layer 142 is made of a moderately doped p-type material, thereby allowing the refractive index of the upper confinement layer 140 to gradually change.

[0046] Please refer to Figure 4 This is a schematic diagram of the optical field distribution of the fundamental mode of a waveguide structure 100 of a semiconductor laser according to an embodiment of this application. The waveguide structure 100 of the semiconductor laser forms an optical field mode due to the refractive index contrast between the etched trench 151 and the ridge waveguide 152. In this embodiment, the waveguide structure 100 of the semiconductor laser has etched trenches 151 of arbitrary width, and the optical field distribution of the fundamental mode is calculated and simulated based on the optical mode, and is shown through the fundamental mode optical field contour line 200. The fundamental mode optical field contour line 200 is confined within the ridge waveguide 152 and is not coupled to the layer body 153. Therefore, in this embodiment, the optical field distribution of the fundamental mode outside the ridge waveguide 152 is below the upper confinement layer 140.

[0047] Please refer to Figure 5 This is a schematic diagram of the optical field distribution of the first-order mode of the waveguide structure 100 of a semiconductor laser according to an embodiment of this application. In this embodiment, the top width W1 and bottom width W2 of the etched trench 151 are both 2 μm, the width W3 of the ridge waveguide 152 is 4 μm, and the thickness of the ridge waveguide 152 is 1 μm. Furthermore, the optical field distribution of the first-order mode is calculated and simulated based on the optical mode, and is shown through the first-order mode optical field contour line 300. The first-order mode optical field contour line 300 is not only confined within the ridge waveguide 152, but also coupled to the layer bodies 153 at both ends. Therefore, in this embodiment, because the optical field of the first-order mode leaks into the heavily doped P-type material of the layer body 153, the heavily doped P-type material of the layer body 153 has a strong absorption effect on light, resulting in increased loss of the first-order mode and an increased lasing threshold. At the same time, higher-order modes are more likely to couple into the layer body 153 than the first-order mode, resulting in greater loss.

[0048] When the coupling condition of "sufficiently narrow etch trench 151" is met, and because the mode field distribution of the first-order mode is wider than that of the fundamental mode, the contour line 300 of the first-order mode optical field will couple into the layer body 153. If the etch trench 151 is too wide, exceeding the mode field size of the first-order mode, it cannot couple to the layer body 153. If the etch trench 151 is too narrow, not only is the processing more difficult, but the light wavelength will also leak, and the excessively narrow etch trench 151 cannot confine the optical field mode. Therefore, this embodiment uses an extremely narrow 2μm etch trench 151. The loss of the higher-order mode increases, but the fundamental mode is not affected. The threshold of the higher-order mode is thus increased, making it less prone to lasing, and the lasing of the fundamental mode is more stable, thereby improving the kink-free power of the output optical power.

[0049] Please refer to Figure 6 This is a schematic diagram of the waveguide structure 100 of a semiconductor laser according to an embodiment of this application. A light-absorbing element 160 is provided on the inner bottom surface of the etched trench 151. The light-absorbing element 160 can serve as a loss layer for absorbing light.

[0050] Since higher-order modes extend to the light absorber 160, the absorption loss of higher-order modes increases, thereby increasing their lasing threshold and indirectly stabilizing the lasing of the fundamental mode. Therefore, in this embodiment, by providing the light absorber 160 on the inner bottom surface of the etched trench 151, the loss of higher-order modes is increased, thereby suppressing the lasing of higher-order modes.

[0051] The waveguide structure 100 of the semiconductor laser also has the following dimensions: W4 - representing the width of the light absorber 160; T2 - representing the thickness of the light absorber 160; HD1 - representing the size of the spacing 161.

[0052] To avoid fundamental mode loss, a gap 161 is left between the optical absorber 160 and the ridge waveguide 152. The size of the gap 161, HD1, is the horizontal distance between the optical absorber 160 and the ridge waveguide 152, and the size of the gap 161, HD1, is 0.5-5μm.

[0053] With the light absorber 160 present, the coupling condition for higher-order modes to the upper confinement layer 140 or the ridge forming layer 150 becomes "the size HD1 of the spacing 161 reaches a preset value," and is independent of the "groove width of the etching trench 151" and the "width W4 of the light absorber 160." Therefore, the bottom width W2 and top width W1 of the etching trench 151 can be any value (i.e., within the range of 0.5-5μm or outside the range of 0.5-5μm, for example, greater than 5μm), and the width W4 of the light absorber 160 can also be any value (i.e., within the range of 0.5-5μm or outside the range of 0.5-5μm), as long as the size HD1 of the spacing 161 is within the preset value range.

[0054] Based on the same principle, the preset value range of the size HD1 of the interval 161 is 0.5-5μm. If the size HD1 of the interval 161 is 0, that is, there is no interval 161, then the fundamental mode will have losses; if the size HD1 of the interval 161 is less than 0.5μm, not only is the processing difficult, but also the light wavelength will leak, making it impossible to limit the optical field mode; if the size HD1 of the interval 161 is greater than 5μm, then higher-order modes cannot be coupled into the light absorber 160, thus failing to suppress higher-order modes; therefore, according to optical mode calculations and simulations, a size HD1 of 0.5-5μm is a more suitable range.

[0055] The thickness T2 of the light-absorbing element 160 is less than or equal to the depth D1 of the etching trench 151. For ease of processing, the thickness T2 of the light-absorbing element 160 is greater than 0.05 μm. In one embodiment, the depth D1 of the etching trench 151 is 0.5-2 μm, and the thickness T2 of the light-absorbing element 160 is 0.5-2 μm. In another embodiment, the depth D1 of the etching trench 151 is 0.5-1 μm, and the thickness of the light-absorbing element is 0.05-0.5 μm.

[0056] In one embodiment, the width W4 of the light absorber 160 can be designed as needed. Since the light absorber 160 is disposed on the inner bottom surface of the etching trench 151, the width W4 of the light absorber 160 is less than or equal to the width W2 of the inner bottom surface of the etching trench 151.

[0057] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A waveguide structure for a semiconductor laser, characterized in that, include: Substrate; A lower limiting layer is disposed on the substrate; A quantum well is disposed on the lower confinement layer; An upper confinement layer is disposed on the quantum well; as well as A ridge forming layer is disposed on the upper confining layer, the ridge forming layer comprising a layer body, etched trenches, and a ridge waveguide; A light field mode is formed by comparing the refractive indices of the etched trench and the ridge waveguide; a light absorber is provided on the inner bottom surface of the etched trench, and the width of the light absorber is less than or equal to the width of the inner bottom surface of the etched trench. The bottom width of the etched trench is 2µm, and the ridge forming layer is made of heavily doped P-type material.

2. The waveguide structure of the semiconductor laser according to claim 1, characterized in that, The substrate is made of heavily doped N-type material.

3. The waveguide structure of the semiconductor laser according to claim 2, characterized in that, The lower constraint layer includes: A first lower confinement layer is disposed on the substrate; and A second lower confinement layer is sandwiched between the first lower confinement layer and the quantum well; The first lower confinement layer is made of a moderately doped N-type material, and the second lower confinement layer is made of an undoped semiconductor material.

4. The waveguide structure of the semiconductor laser according to claim 2, characterized in that, The upper constraint layer includes: A first upper confinement layer is disposed on the quantum well; and The second upper confining layer is sandwiched between the first upper confining layer and the ridge forming layer; The first upper confinement layer is made of undoped semiconductor material, and the second upper confinement layer is made of moderately doped P-type material.

5. The waveguide structure of the semiconductor laser according to claim 1, characterized in that, The etching trenches are provided in multiple ways, and the etching trenches are rectangular grooves; The ridge waveguide is sandwiched between two adjacent etched trenches, and the cross-section of the ridge waveguide along the thickness direction is rectangular.

6. The waveguide structure of the semiconductor laser according to any one of claims 1 to 5, characterized in that, A gap is left between the light-absorbing element and the ridge waveguide.

7. The waveguide structure of the semiconductor laser according to claim 1, characterized in that, The thickness of the light-absorbing element is less than or equal to the depth of the etched trench.

8. The waveguide structure of the semiconductor laser according to claim 7, characterized in that, The depth of the etched trench is 0.5-2µm, and the thickness of the light-absorbing element is 0.05-1µm.

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