Diffraction type surface emitting semiconductor laser and preparation method thereof

Abstract

The invention provides a diffraction type surface-emitting semiconductor laser and a preparation method thereof. The diffraction type surface-emitting semiconductor laser comprises an active layer and complementary optical modulation layers located in one or more of an upper cladding, an upper waveguide layer, a lower waveguide layer and a lower cladding, and the complementary optical modulation layers comprise an upper optical modulation layer and a lower optical modulation layer; the lower optical modulation layer is provided with a first optical modulation material and a second optical modulation material which have different refractive indexes, and the two types of optical modulation materials form a high-low refractive index difference; the upper optical modulation layer is provided with a third optical modulation material and a fourth optical modulation material which are different in refractive index, and the two types of optical modulation materials form a high-low refractive index difference; in the direction perpendicular to the laser emitting face, the area where the second optical modulation material is located corresponds to the area where the fourth optical modulation material is located, and the area where the first optical modulation material is located corresponds to the area where the third optical modulation material is located.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor lasers, and in particular to a diffraction type surface emitting semiconductor laser and a preparation method thereof. Background Art

[0002] In 2022, Kyoto University in Japan published a technical route for achieving high-power single-mode output of photonic crystal surface-emitting lasers (PCSEL) (Reference 1). The following year, they reported a PCSEL with a continuous output power of 50W, a divergence angle of less than 0.05°, and a brightness of 1GW / cm 2 ·sr. PCSEL is a horizontal cavity surface emission structure. It uses a flat waveguide structure to make the light field in the z direction the fundamental mode. A photonic crystal structure is made in the cladding. The diffraction effect of the second-order grating is used to generate the diffraction component in the z direction to achieve surface emission. Similarly, using a ring grating instead of a photonic crystal can also achieve surface emission, but there is a difference in the light field distribution between the two. In 1990, Dr. Toda performed theoretical calculations on disk-shaped DFB lasers. Dr. PL Greene and Professor DG Hall of the University of Rochester calculated the light field distribution corresponding to different angular modes m (Reference 2). Dr. Sun Xiankai and Professor A. Yariv of the California Institute of Technology modeled and analyzed the ring DFB structure, disk Bragg structure, and circular microcavity Bragg structure and performed theoretical calculations (Reference 3).

[0003] PCSEL adopts a dual lattice structure, using the phase difference between the small circular hole and the elliptical hole to partially offset the light field intensity and reduce the in-plane feedback. The ring grating structure can reduce the in-plane feedback by adjusting the duty cycle of the grating to close to 0.5. However, both structures are optimized for the pattern.

[0004] Prior art literature Document 1: Takuya Inoue, Masahiro Yoshida, John Gelleta, et al., General recipe to realize photonic-crystal surface-emitting lasers with 100-W-to-1-kWsingle-mode operation, Nature Communications, Vol. 13, 2022. Document 2: Pamela L. Greene, Radiation from Circular-Grating DistributedFeedback Lasers[D], University of Rochester, 2000. Document 3: Xiankai Sun, Supermode Si / III-V Lasers and Circular BraggLasers[D], California Institute of Technology, 2010. Summary of the invention Based on this, the present invention aims to provide an improved diffraction-type surface emitting semiconductor laser and a method for preparing the same, so as to solve at least one of the following problems.

[0005] In a first aspect, the present application provides a diffraction-type surface emitting semiconductor laser, comprising an upper cladding layer, an upper waveguide layer, an active layer, a lower waveguide layer, and a lower cladding layer, wherein when carriers are injected into the active layer, the active layer emits light, and the diffraction-type surface emitting semiconductor laser further comprises: A complementary optical modulation layer, located in one or more of the upper cladding layer, the upper waveguide layer, the lower waveguide layer, and the lower cladding layer; The complementary optical modulation layer comprises an upper optical modulation layer and a lower optical modulation layer; The lower optical modulation layer comprises a first optical modulation material having a first refractive index and a second optical modulation material having a second refractive index, the first refractive index is different from the second refractive index, and the second optical modulation material is distributed in the first optical modulation material to form a high and low refractive index difference; The upper optical modulation layer includes a third optical modulation material having a third refractive index and a fourth optical modulation material having a fourth refractive index, wherein the third refractive index is different from the fourth refractive index, and the third optical modulation material is distributed in the fourth optical modulation material to form a high and low refractive index difference; In a direction perpendicular to the laser emitting surface, the region where the second optical modulation material is located corresponds to the region where the fourth optical modulation material is located, and the region where the first optical modulation material is located corresponds to the region where the third optical modulation material is located.

[0006] The above-mentioned diffraction-type surface-emitting semiconductor laser, by adopting a spatially complementary double-layer optical modulation layer, partially cancels out the feedback intensity in the xy plane, thereby further reducing the in-plane feedback intensity, which is beneficial for the device to achieve single-mode output in a large area. In addition, through the epitaxial process, a layer of low-refractive index material is grown simultaneously in the double-layer optical modulation layer and on the surface of the waveguide / cladding, and then the substrate material is grown, so that the interface defects of the double-layer optical modulation layer are low, which can reduce non-radiative recombination. This structure and process are also suitable for arranging the double-layer optical modulation layer in the waveguide layer to improve the regulation of the light field.

[0007] In one embodiment, the lower optical modulation layer is a first photonic crystal layer or a first grating layer, and the upper optical modulation layer is a second photonic crystal layer or a second grating layer.

[0008] In one embodiment, when the second optical modulation material and the fourth optical modulation material are low-refractive materials, the first optical modulation material and the third optical modulation material are high-refractive materials; when the second optical modulation material and the fourth optical modulation material are high-refractive materials, the first optical modulation material and the third optical modulation material are low-refractive materials.

[0009] In one embodiment, the first optical modulation material and the fourth optical modulation material are the same material; the second optical modulation material and the third optical modulation material are the same material.

[0010] In one of the embodiments, a waveguide layer or a cladding layer is further disposed between the upper optical modulation layer and the lower optical modulation layer.

[0011] In one of the embodiments, the thickness of the upper optical modulation layer and the lower optical modulation layer are equal.

[0012] In one of the embodiments, the upper optical modulation layer and the lower optical modulation layer are located in the upper waveguide layer or the lower waveguide layer; the upper cladding layer, the upper waveguide layer, the active layer, the lower waveguide layer, and the lower cladding layer constitute an epitaxial layer; and a first-order mode exists in the optical field in the z direction perpendicular to the epitaxial layer.

[0013] In one of the embodiments, the emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, and the period a=λ / n; the active layer is located within the range of ±a of a wave peak of the first-order mode of the light field in the z direction.

[0014] In one of the embodiments, the upper optical modulation layer and the lower optical modulation layer are located within a range of ±a of another peak of the first-order mode of the light field in the z direction.

[0015] In one of the embodiments, the thickness of the upper optical modulation layer and the lower optical modulation layer does not exceed 0.5a.

[0016] In one of the embodiments, the distance between the upper optical modulation layer and the lower optical modulation layer does not exceed 0.7a.

[0017] In one of the embodiments, an electron blocking layer is further included, and the diffraction-type surface emitting semiconductor laser forms a structure of a lower cladding layer, a lower waveguide layer, an active layer, a first upper waveguide layer, an electron blocking layer, a second upper waveguide layer, the lower optical modulation layer, a third upper waveguide layer, the upper optical modulation layer, a fourth upper waveguide layer, and an upper cladding layer from bottom to top.

[0018] In one of the embodiments, the electron blocking layer is located within the range of ±0.35a of the node of the first-order mode of the optical field in the z direction.

[0019] In a second aspect, the present application provides a method for preparing a diffraction-type surface emitting semiconductor laser, the preparation method adopts an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer, characterized in that the method further comprises: forming a photonic crystal hole or a grating groove structure on the second p-type waveguide layer through a patterning and etching process; epitaxially growing a low refractive index or a high refractive index material in the hole or groove structure and on the second p-type waveguide layer; and continuing to epitaxially grow a p-type waveguide layer and a p-type cladding layer.

[0020] The above preparation method generates a complementary double-layer photonic crystal or grating structure, so that the feedback intensity in the xy plane is partially offset, thereby further reducing the in-plane feedback intensity, which is beneficial for the device to achieve single-mode output in a large area.

[0021] In a third aspect, the present application provides a method for preparing a diffraction-type surface emitting semiconductor laser, the preparation method adopts an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer, the method further comprising: forming a photonic crystal hole or a grating groove structure on the third n-type waveguide layer through a patterning and etching process; epitaxially growing a low refractive index or high refractive index material in the hole or groove structure and on the third n-type waveguide layer; and continuing to epitaxially grow an n-type waveguide layer, a quantum well, a p-type waveguide layer, and a p-type cladding layer.

[0022] The above preparation method generates a complementary double-layer photonic crystal or grating structure, so that the feedback intensity in the xy plane is partially offset, thereby further reducing the in-plane feedback intensity, which is beneficial for the device to achieve single-mode output in a large area.

[0023] In one embodiment, after the p-type waveguide layer is grown, the method further includes: growing an electron blocking layer; and finally growing a p-type cladding layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the implementation methods of this specification or the technical solutions in the prior art, the drawings required for use in the implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some implementation methods recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0025] Figure 1 A cross-sectional schematic diagram of a diffraction-type surface emitting semiconductor laser structure according to an embodiment of the present application; Figure 2 A schematic cross-sectional view of a diffraction-type surface emitting semiconductor laser structure according to another embodiment of the present application; Figure 3 A cross-sectional schematic diagram of a diffraction-type surface emitting semiconductor laser structure according to another embodiment of the present application Figure 4(a) shows the Figure 3 The fundamental mode light field distribution of the GaN-based laser with the structure in the z direction; Figure 4(b) shows the Figure 3 The first-order mode light field distribution of the GaN-based laser with the structure in the z direction; FIG5( a ) shows the relationship between the thickness of the third upper waveguide layer 43 and the emission coefficient in Example 3; FIG5( b ) shows the diffracted light intensity distribution of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction when the emission coefficient of Example 3 is the maximum; FIG5( c ) shows the diffraction light intensity distribution of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction when the exit coefficient of Example 3 is the smallest; Figure 6 The relationship between the exit coefficient of Example 4 and the third upper waveguide layer 43 is shown; Figure 7 The light field distribution of the PCSEL structure of Comparative Example 2 in the z direction is shown. DETAILED DESCRIPTION

[0026] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0027] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0029] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0030] PCSEL uses a dual lattice structure to reduce in-plane feedback, and the annular grating structure adjusts in-plane feedback by changing the grating duty cycle. These two methods not only have limited ability to reduce feedback, but are also sensitive to the size and structure of the photonic crystal / grating, and the uniformity of the pattern will also affect the final effect.

[0031] Based on the above problems, the embodiment of the present application provides a diffraction-type surface-emitting semiconductor laser. By adopting a spatially complementary double-layer photonic crystal or grating structure, the feedback intensity in the xy plane is partially offset, thereby further reducing the in-plane feedback intensity, which is beneficial for the device to achieve single-mode output in a large area. And through the epitaxial process, a layer of low-refractive index material is grown in the photonic crystal hole or grating groove and on the waveguide / cladding surface at the same time, and then the substrate material is grown, so that the interface defects of the double-layer photonic crystal or grating structure are low, which can reduce non-radiative recombination. This structure and process are also suitable for setting a double-layer photonic crystal or grating structure in a waveguide layer to improve the regulation of the light field.

[0032] like Figure 1 and Figure 2 As shown, the embodiment of the present application provides a diffraction-type surface emitting semiconductor laser 100, which includes, from top to bottom, an upper cladding 8, an upper waveguide layer 4, an active layer 3, a lower waveguide layer 2, and a lower cladding 1. When carriers are injected into the active layer 3, the active layer 3 emits light. The diffraction-type surface emitting semiconductor laser 100 also includes: a complementary optical modulation layer, which is located in one or more layers of the upper cladding 8, the upper waveguide layer 4, the lower waveguide layer 2, and the lower cladding 1.

[0033] Among them, the complementary optical modulation layer includes an upper optical modulation layer 9 and a lower optical modulation layer 7 that have a complementary relationship in space; the lower optical modulation layer 7 includes a first optical modulation material with a first refractive index and a second optical modulation material with a second refractive index, the first refractive index is different from the second refractive index, and the second optical modulation material forms a high-low refractive index difference with the first optical modulation material. Optionally, the second optical modulation material can be distributed in the first optical modulation material to form a structure with a high-low refractive index difference. The upper optical modulation layer 9 includes a third optical modulation material with a third refractive index and a fourth optical modulation material with a fourth refractive index, the third refractive index is different from the fourth refractive index, and the third optical modulation material forms a high-low refractive index difference with the fourth optical modulation material. Optionally, the third optical modulation material can be distributed in the fourth optical modulation material to form a structure with a high-low refractive index difference. In the direction perpendicular to the laser exit surface, the area where the second optical modulation material is located corresponds to the area where the fourth optical modulation material is located, and the area where the first optical modulation material is located corresponds to the area where the third optical modulation material is located.

[0034] Exemplarily, when the second optical modulation material and the fourth optical modulation material are low refractive materials, the first optical modulation material and the third optical modulation material are high refractive materials; when the second optical modulation material and the fourth optical modulation material are high refractive materials, the first optical modulation material and the third optical modulation material are low refractive materials.

[0035] In some embodiments, see Figures 1 to 3 , the lower optical modulation layer 7 is the first photonic crystal layer or the first grating layer, and the upper optical modulation layer 9 is the second photonic crystal layer or the second grating layer. Optionally, the lower optical modulation layer 7 and the upper optical modulation layer 9 can be arranged in the following form: the surrounding material of the lower optical modulation layer 7 (corresponding to the first optical modulation material) is the surrounded material of the upper optical modulation layer 9 (corresponding to the third optical material), and the surrounded material of the lower optical modulation layer 7 (corresponding to the second optical modulation material) is the surrounding material of the upper optical modulation layer 9 (corresponding to the fourth optical modulation material), so as to realize the complementary relationship between the materials of the lower optical modulation layer 7 and the upper optical modulation layer 9 in spatial position, thereby partially offsetting the feedback intensity in the xy plane, and realizing the reduction of in-plane feedback. Optionally, the photonic crystal can be an array-type photonic crystal or a ring-type photonic crystal; the grating can be a ring-type grating.

[0036] Exemplarily, the upper cladding layer can be an n-type cladding layer or a p-type cladding layer, and the corresponding lower cladding layer is a p-type cladding layer or an n-type cladding layer. The upper waveguide layer can be an n-type waveguide layer or a p-type waveguide layer, and the corresponding lower waveguide layer is a p-type waveguide layer or an n-type waveguide layer.

[0037] In some embodiments, Figure 1 As shown, the upper optical modulation layer 9 may be disposed in the upper cladding layer 8 , for example, the upper optical modulation layer 9 may be disposed between the first upper cladding layer 81 and the second upper cladding layer 82 .

[0038] In some embodiments, the lower optical modulation layer 7 and the upper optical modulation layer 9 are located in the upper waveguide layer 4, or the lower optical modulation layer 7 and the upper optical modulation layer 9 are located in the lower waveguide layer 2, and a first-order mode exists in the z-direction optical field perpendicular to the epitaxial layer. Figure 2 As shown, the lower optical modulation layer 7 and the upper optical modulation layer 9 can be arranged in the upper waveguide layer 4, for example, the lower optical modulation layer 7 can be arranged between the first upper waveguide layer 41 and the third upper waveguide layer 43, and the upper optical modulation layer 9 can be arranged between the third upper waveguide layer 43 and the fourth upper waveguide layer 44. By changing the positions of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z-direction optical field, the in-plane feedback intensity can be adjusted to adapt to the device area.

[0039] In some embodiments, a waveguide layer or a cladding layer is further disposed between the lower optical modulation layer 7 and the upper optical modulation layer 9. Figure 1 As shown, a first upper cladding layer 81 is provided between the lower optical modulation layer 7 and the upper optical modulation layer 9; or Figure 2 As shown, a third upper waveguide layer 43 is disposed between the lower optical modulation layer 7 and the upper optical modulation layer 9. By controlling the thickness of the first upper cladding layer 81 or the third upper waveguide layer 43, the phase of diffraction generated by the lower optical modulation layer 7 and the upper optical modulation layer 9 can be adjusted, so as to facilitate the in-phase superposition of the two to obtain the maximum vertical emission coefficient.

[0040] In some embodiments, the emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, the period a=λ / n, and the active layer is located within the range of ±a of a wave crest of the first-order mode of the light field in the z direction, for example, it can be located at a wave crest of ±a, ±0.8a, ±0.6a, ±0.4a, ±0.2a, etc. By locating the lower optical modulation layer 7 and the upper optical modulation layer 9 near a wave crest of the first-order mode, it is beneficial to obtain a larger vertical emission coefficient.

[0041] When the lower optical modulation layer 7 and the upper optical modulation layer 9 are located on one side of a wave crest of the light field distribution in the z direction (which can be a fundamental mode, a first-order mode or a higher-order mode), part of the feedback intensity is offset, and a larger in-plane feedback intensity is obtained; when the lower optical modulation layer 7 and the upper optical modulation layer 9 are located on both sides of one of the wave crests of the first-order mode or a higher-order mode in the z direction, the in-plane feedback intensity generated by the two layers is close, the offset effect is significant, and the in-plane feedback intensity is low. Preferably, the thickness of the lower optical modulation layer 7 and the upper optical modulation layer 9 are equal.

[0042] Optionally, the lower optical modulation layer 7 and the upper optical modulation layer 9 are located within the range of ±a of a wave crest of the first-order mode of the light field in the z direction, for example, they may be located at another wave crest of ±a, ±0.8a, ±0.6a, ±0.4a, ±0.2a, etc. Such a setting is conducive to obtaining a larger vertical emission coefficient.

[0043] Optional, according to Figure 6 It can be seen that in order to obtain a maximum value, the thickness of the lower optical modulation layer 7 and the upper optical modulation layer 9 does not exceed 0.5a, for example, it can be 0.5a, 0.4a, 0.3a, 0.2a, 0.1a, etc. Optionally, according to FIG5 (a), in order to obtain a point near the maximum value, the distance between the lower optical modulation layer 7 and the upper optical modulation layer 9 does not exceed 0.7a, for example, it can be 0.7a, 0.6a, 0.5a, 0.4a, 0.3a, 0.2a, 0.1a, etc.

[0044] In some embodiments, the diffraction-type surface emitting semiconductor laser further includes an electron blocking layer (EBL layer) 5, and forms a structure of a lower cladding layer 1, a lower waveguide layer 2, an active layer 3, a first upper waveguide layer 41, an electron blocking layer 5, a second upper waveguide layer 42, a lower optical modulation layer 7, a third upper waveguide layer 43, an upper optical modulation layer 9, a fourth upper waveguide layer 44, and an upper cladding layer 8 from bottom to top. By utilizing the first-order mode or higher-order mode of the light field in the z direction, the electron blocking layer 5 is inserted into the upper waveguide layer 4 and placed near the node of the light field, which is beneficial to reduce the non-radiative loss caused by the layer and improve the electron-hole recombination rate. Optionally, the electron blocking layer 5 is located within the range of ±0.35a of the node of the first-order mode of the light field in the z direction, for example, it can be located at the node ±0.35a, ±0.3a, ±0.2a, ±0.1a, etc. Since the refractive index of the cladding material is lower than that of the waveguide layer material, the light field can be mostly confined in the waveguide layer (propagating in the xy plane), that is, the light field intensity in the z direction is mostly distributed in the waveguide layer. Therefore, by adjusting the refractive index and thickness of the cladding and waveguide layer materials, it is beneficial to make the light field in the z direction a first-order mode and the electron blocking layer 5 be near the node of the first-order mode.

[0045] The embodiment of the present application also provides a method for preparing a diffraction-type surface emitting semiconductor laser. The preparation method adopts an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer. The preparation method also includes: forming a photonic crystal hole or a grating groove structure on the second p-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive index or high-refractive index material in the hole or groove structure and on the second p-type waveguide layer; and continuing to epitaxially grow a p-type waveguide layer and a p-type cladding layer.

[0046] The embodiment of the present application also provides a method for preparing a surface emitting semiconductor laser. The method adopts an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer. The method further includes: forming a photonic crystal hole or a grating groove structure on the third n-type waveguide layer through a patterning and etching process; epitaxially growing a low-refractive index or high-refractive index material in the hole or groove structure and on the third n-type waveguide layer; and continuing to epitaxially grow an n-type waveguide layer, a quantum well, a p-type waveguide layer, and a p-type cladding layer.

[0047] In some embodiments, after the p-type waveguide layer is grown, the preparation method further includes: growing an electron blocking layer; and finally growing a p-type cladding layer.

[0048] The structure and effect of the diffraction-type surface emitting semiconductor laser of the above-mentioned embodiments will be further described below through several embodiments and comparative examples.

[0049] Example 1 Taking GaN-based semiconductor laser as an example, Figure 1 In the structure shown, a double-layer grating structure is set in the upper cladding layer 8. The first grating layer 7 is p-GaN surrounded by ITO, the first upper cladding layer 81 is p-GaN, and the second grating layer 9 is ITO surrounded by p-GaN. The calculated absolute value of the in-plane feedback coefficient is: 4.56×10 -5 .

[0050] Comparative Example 1 Based on Example 1, remove Figure 1 The first upper cladding layer 81 and the second grating layer 9 in the structure, the calculated absolute value of the in-plane feedback coefficient is: 3.45×10 -4 .

[0051] In comparative example 1, the grating layer is only the first grating layer 7 of p-GaN surrounded by ITO, and the high and low refractive index differences formed produce in-plane feedback. In Example 1, a second grating layer 9 of ITO surrounded by p-GaN is added, and its material structure is opposite to that of the first grating layer 7, and the in-plane feedback phase difference generated is π, which partially offsets the in-plane feedback generated by the first grating layer 7, so the absolute value of the in-plane feedback coefficient is closer to 0.

[0052] Example 2 Figure 2 The light field distribution of the structure shown in the z direction is Figure 3 Considering the structure shown in Figure 2 In the structure of the waveguide layer 4, the waveguide layer 4 is relatively thick. In order to increase the recombination rate of electrons and holes in the active layer 3, an electron blocking layer (EBL layer) can be added in the area near the active layer 3 to form Figure 3 The structure shown. Since the EBL layer is heavily doped, which will cause non-radiative recombination, the EBL layer is placed near the node of the first-order mode in the z direction. In this way, the EBL layer can be placed in the waveguide layer, which is different from the traditional structure (EBL layer in the cladding).

[0053] use Figure 3 The structure shown in the figure takes the 435nmGaN-based semiconductor laser as an example. Under the same epitaxial structure, the optical field distribution of the fundamental mode and the first-order mode in the z direction are calculated, as shown in Figure 4 (a) and Figure 4 (b). Since the thickness of the waveguide layer (upper waveguide layer + active layer + lower waveguide layer) is greater than 1μm, there are first-order modes or higher-order modes. As shown in Figure 4 (a), the highly doped EBL layer is located near the peak, which increases the fundamental mode loss. In the first-order mode (Figure 4 (b)), the EBL layer is at the node and will not significantly increase the device loss. After calculation, when the EBL layer is 20nm, the device loss Г EBL ≈0.07%; when the EBL layer is 60nm, Г EBL ≈0.56%; when the EBL layer is 120nm, Г EBL ≈2.20%. Calculating the effective refractive index of the first-order mode of the structure, the wavelength of 435nm light in the material is about 174mn (that is, the period a), so the EBL layer of 120nm is equivalent to about 0.7 times the period a. Correspondingly, when the EBL layer is 60nm, it is equivalent to 0.34a; when the EBL layer is 20nm, it is equivalent to 0.11a.

[0054] Example 3 use Figure 3In the structure shown, the lower optical modulation layer 7 and the upper optical modulation layer 9 are set to 40nm. Changing the thickness of the third upper waveguide layer 43 can adjust the phase of the diffracted light of the lower optical modulation layer 7 and the upper optical modulation layer 9, thereby controlling the change of the exit coefficient. The relationship between the thickness of the third upper waveguide layer 43 and the exit coefficient is shown in Figure 5 (a). When the thickness of the third upper waveguide layer 43 is 72nm, the exit coefficient is the largest. At this time, the diffracted light intensity distribution of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction is shown in Figure 5 (b). When the thickness of the third upper waveguide layer 43 is 136nm, the exit coefficient is the smallest. At this time, the diffracted light intensity distribution of the lower optical modulation layer 7 and the upper optical modulation layer 9 in the z direction is shown in Figure 5 (c). Combined with the actual process, preferably, the thickness of the third upper waveguide layer 43 or the first upper cladding layer 81 does not exceed 120nm, which is equivalent to 0.7 times the period a.

[0055] Example 4 use Figure 3 In the structure shown in FIG. 1 , when the lower optical modulation layer 7 and the upper optical modulation layer 9 are set to 40 nm, 70 nm and 90 nm respectively, the emission coefficients corresponding to different thicknesses of the third upper waveguide layer 43 are calculated, as shown in FIG. Figure 6 When the thickness of the third upper waveguide layer 43 is too large, it is greater than 90nm in the calculated structure. The thickness of the third upper waveguide layer 43 has no maximum value when it is less than 100nm. Therefore, the thickness of the third upper waveguide layer 43 or the first upper cladding layer 81 should be less than a certain value to obtain the maximum exit coefficient. In combination with the actual process, preferably, the thickness of the lower optical modulation layer 7 and the upper optical modulation layer 9 does not exceed 90nm, which is equivalent to 0.5 times the period a.

[0056] It can also be inferred from Figure 4 (b) that the active layer 3 should be located within ±174nm of a peak of the first-order mode, that is, the active layer is within the range of ±a of a peak of the first-order mode; the lower optical modulation layer 7 and the upper optical modulation layer 9 should be located within ±174nm of another peak of the first-order mode, that is, within the range of ±a of another peak of the first-order mode.

[0057] Example 5 refer to Figure 3 For the structure shown, when the lower cladding layer 1 is an n-type material and the upper cladding layer 8 is a p-type material, the process steps are as follows: The n-type cladding layer, n-type waveguide layer, quantum well, first p-type waveguide layer, EBL layer, and second p-type waveguide layer are grown layer by layer using an epitaxial growth process. A photonic crystal hole or grating groove structure is formed on the second p-type waveguide layer through patterning and etching processes. Then, a material with a low refractive index and a higher bandgap width is epitaxially grown to partially fill the photonic crystal hole or grating groove with the low refractive index material on the one hand, and epitaxially grow the low refractive index material in the unetched area of ​​the second p-type waveguide layer on the other hand. Next, a p-type waveguide layer with a certain thickness is epitaxially grown, and the material is the same as that of the second p-type waveguide layer. Finally, a p-cladding layer is epitaxially grown.

[0058] Example 6 refer to Figure 2 For the structure shown, when the lower cladding layer 1 is a p-type material and the upper cladding layer 8 is an n-type material, the process steps are as follows: The n-cladding layer and the third n-waveguide layer are grown layer by layer by epitaxial growth process. A photonic crystal hole or grating groove structure is formed on the third n-waveguide layer by patterning and etching process. Then, a material with a low refractive index and a higher bandgap width is epitaxially grown to partially fill the photonic crystal hole or grating groove with the low refractive index material, and the low refractive index material is also epitaxially grown in the unetched area of ​​the third n-waveguide layer. Then, a certain thickness of n-type waveguide layer, quantum well, p-type waveguide layer, EBL layer, and p-type cladding layer are epitaxially grown.

[0059] Comparative Example 2 According to the GaAs-based PCSEL structure disclosed in Reference 1, the period is about 280nm, and the distribution of the fundamental mode of the light field in the z direction is calculated, as follows: Figure 7 As shown. In the z direction, it is the fundamental mode, the total thickness of the waveguide layer is about 300nm, which is about one period. Figure 7 It can be seen that on the one hand, the thickness of the waveguide layer is relatively thin, so the growth of each layer of material needs to be precisely controlled. On the other hand, the photonic crystal layer is in the cladding, and its limitation factor is relatively large, resulting in large losses and affecting the efficiency of the device.

[0060] It should be noted that the numbers representing quantities or properties used to describe and claim certain embodiments of the present application should be understood to be modified by the terms "roughly", "about", "approximately" or "substantially" in some cases. For example, unless otherwise specified, "roughly", "about", "approximately" or "substantially" can indicate a ±20% variation of the value described. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may change according to the required features of individual embodiments. In some embodiments, the numerical parameters should take into account the specified significant digits and adopt the general method of retaining digits. Although the numerical domains and parameters used to confirm the breadth of their range in some embodiments of the present application are approximate values, in specific embodiments, the setting of such numerical values ​​is as accurate as possible within the feasible range.

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A diffraction-type surface-emitting semiconductor laser, comprising, from top to bottom, an upper cladding layer, an upper waveguide layer, an active layer, a lower waveguide layer, and a lower cladding layer, wherein when carriers are injected into the active layer, the active layer emits light, characterized in that: The diffraction type surface emitting semiconductor laser further comprises: A complementary optical modulation layer, located in one or more of the upper cladding layer, the upper waveguide layer, the lower waveguide layer, and the lower cladding layer; The complementary optical modulation layer comprises an upper optical modulation layer and a lower optical modulation layer; The lower optical modulation layer includes a first optical modulation material having a first refractive index and a second optical modulation material having a second refractive index, the first refractive index is different from the second refractive index, and the second optical modulation material forms a high-low refractive index difference with the first optical modulation material; The upper optical modulation layer includes a third optical modulation material having a third refractive index and a fourth optical modulation material having a fourth refractive index, the third refractive index is different from the fourth refractive index, and the third optical modulation material and the fourth optical modulation material form a high-low refractive index difference; In a direction perpendicular to the laser emitting surface, the region where the second optical modulation material is located corresponds to the region where the fourth optical modulation material is located, and the region where the first optical modulation material is located corresponds to the region where the third optical modulation material is located.

2. The diffraction type surface emitting semiconductor laser according to claim 1, characterized in that: The lower optical modulation layer is a first photonic crystal layer or a first grating layer, and the upper optical modulation layer is a second photonic crystal layer or a second grating layer.

3. The diffraction type surface emitting semiconductor laser according to claim 2, characterized in that: When the first optical modulation material and the fourth optical modulation material are low-refractive materials, the second optical modulation material and the third optical modulation material are high-refractive materials; when the first optical modulation material and the fourth optical modulation material are high-refractive materials, the second optical modulation material and the third optical modulation material are low-refractive materials.

4. The diffraction type surface emitting semiconductor laser according to claim 3, characterized in that: The first optical modulation material and the fourth optical modulation material are the same material; the second optical modulation material and the third optical modulation material are the same material.

5. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 4, characterized in that: A waveguide layer or a cladding layer is further arranged between the upper optical modulation layer and the lower optical modulation layer.

6. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 4, characterized in that: The upper optical modulation layer and the lower optical modulation layer have the same thickness.

7. The diffraction type surface emitting semiconductor laser according to any one of claims 1 to 4, characterized in that: The upper optical modulation layer and the lower optical modulation layer are located in the upper waveguide layer or the lower waveguide layer; the upper cladding layer, the upper waveguide layer, the active layer, the lower waveguide layer, and the lower cladding layer constitute an epitaxial layer; There is a first-order mode in the z-direction optical field perpendicular to the epitaxial layer.

8. The diffraction type surface emitting semiconductor laser according to claim 7, characterized in that: The emission wavelength of the laser is λ, the effective refractive index of the first-order mode is n, and the period a=λ / n; the active layer is located within the range of ±a of a wave peak of the first-order mode of the light field in the z direction.

9. The diffraction type surface emitting semiconductor laser according to claim 8, characterized in that: The upper optical modulation layer and the lower optical modulation layer are located within a range of ±a of another peak of the first-order mode of the light field in the z direction.

10. The diffraction type surface emitting semiconductor laser according to claim 9, characterized in that: The thickness of the upper optical modulation layer and the lower optical modulation layer does not exceed 0.5a.

11. The diffraction type surface emitting semiconductor laser according to claim 9 or 10, characterized in that: The distance between the upper optical modulation layer and the lower optical modulation layer does not exceed 0.7a.

12. The diffraction type surface emitting semiconductor laser according to claim 7, characterized in that: It also includes an electron blocking layer. The diffraction-type surface emitting semiconductor laser forms a structure of a lower cladding layer, a lower waveguide layer, an active layer, a first upper waveguide layer, an electron blocking layer, a second upper waveguide layer, the lower optical modulation layer, a third upper waveguide layer, the upper optical modulation layer, a fourth upper waveguide layer, and an upper cladding layer from bottom to top.

13. The diffraction type surface emitting semiconductor laser according to claim 12, characterized in that: The electron blocking layer is located within the range of ±0.35a of the node of the first-order mode of the light field in the z direction.

14. A method for preparing a diffraction-type surface-emitting semiconductor laser, the method adopting an epitaxial growth process to grow an n-type cladding layer, an n-type waveguide layer, a quantum well, a first p-type waveguide layer, an electron blocking layer, and a second p-type waveguide layer layer by layer, characterized in that: The method further comprises: Forming a photonic crystal hole or grating groove structure on the second p-type waveguide layer through patterning and etching processes; epitaxially growing a material with a low refractive index or a high refractive index in the empty hole or groove structure and on the second p-type waveguide layer; Continue to epitaxially grow the p-type waveguide layer and the p-type cladding layer.

15. A method for preparing a diffraction-type surface-emitting semiconductor laser, the method adopting an epitaxial growth process to grow an n-type cladding layer and a third n-type waveguide layer layer by layer, the method further comprising: Forming a photonic crystal hole or grating groove structure on the third n-type waveguide layer through patterning and etching processes; epitaxially growing a material with a low refractive index or a high refractive index in the empty hole or groove structure and on the third n-type waveguide layer; Continue to epitaxially grow the n-type waveguide layer, quantum well, p-type waveguide layer, and p-type cladding layer.

16. The preparation method according to claim 15, characterized in that: After growing the p-type waveguide layer, the method further comprises: growing an electron blocking layer; Finally, the p-type cladding layer is grown.

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