Mode-controlled semiconductor light-emitting structure and preparation method thereof

Abstract

The present invention provides a mode-regulated semiconductor light-emitting structure and a preparation method thereof. The mode-regulated semiconductor light-emitting structure comprises: a first limiting layer, a first waveguide layer, an active layer, a second waveguide layer and a second limiting layer stacked in sequence; a grating layer located between the first limiting layer and the active layer and / or between the second limiting layer and the active layer; wherein the grating layer comprises: a plurality of grating strips arranged at intervals along the cavity length direction; at least a portion of the grating strips have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-regulated semiconductor light-emitting structure along the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a mode-regulated semiconductor light-emitting structure and a preparation method thereof. Background Art

[0002] Semiconductor light-emitting devices are devices that use certain semiconductor materials as working materials to produce stimulated emission. Their working principle is: through a certain excitation method, a particle population inversion of non-equilibrium carriers is achieved between the energy bands (conduction band and valence band) of the semiconductor material, or between the energy bands of the semiconductor material and the energy levels of impurities (acceptor or donor). When a large number of electrons in the particle population inversion state recombine with holes, stimulated emission occurs. Semiconductor light-emitting devices are widely used due to their small size and high electro-optical conversion efficiency. Summary of the invention

[0003] Therefore, the technical problem to be solved by the present invention is how to balance the problem of increasing the light output power and reducing the spectrum width, thereby providing a mode-controlled semiconductor light-emitting structure and a preparation method thereof.

[0004] The present invention provides a mode-regulated semiconductor light-emitting structure, comprising: a first limiting layer, a first waveguide layer, an active layer, a second waveguide layer and a second limiting layer stacked in sequence; a grating layer located between the first limiting layer and the active layer and / or between the second limiting layer and the active layer; wherein the grating layer comprises: a plurality of grating strips arranged at intervals along the cavity length direction; at least a portion of the grating strips have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-regulated semiconductor light-emitting structure along the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction.

[0005] Optionally, the length of the grating strip with the shortest length in the slow axis direction among the plurality of grating strips is 2 μm to 10 μm.

[0006] Optionally, the length of the grating strip with the longest length in the slow axis direction among the plurality of grating strips is 80% to 100% of the size of the active layer in the slow axis direction.

[0007] Optionally, the grating layer includes a plurality of grating groups arranged in the cavity length direction, each grating group includes a plurality of grating strips arranged at intervals along the cavity length direction, and at least some of the grating strips in the grating groups have different lengths in the slow axis direction.

[0008] Optionally, the lengths of the multiple grating bars in the grating group in the slow axis direction first increase and then decrease from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating bars in the grating group in the slow axis direction increase gradually from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating bars in the grating group in the slow axis direction decrease gradually from the front cavity surface to the rear cavity surface.

[0009] Optionally, the multiple grating groups include a first grating group to an M-th grating group, where M is an integer greater than or equal to 2; wherein the depths of the grating bars in the first grating group to the M-1-th grating group in the fast axis direction are respectively less than the depths of the grating bars in the M-th grating group in the fast axis direction, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface to the M-th grating group and does not extend to the rear cavity surface.

[0010] Optionally, the plurality of grating groups include a first grating group to an Mth grating group, where M is an integer greater than or equal to 2; and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from a front cavity surface to a rear cavity surface.

[0011] Optionally, the depths of the grating strips in the first grating group to the Mth grating group in the fast axis direction are the same.

[0012] Optionally, the lengths of the multiple grating strips in the grating layer in the slow axis direction first increase and then decrease from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating strips in the grating layer in the slow axis direction increase gradually from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating strips in the grating layer in the slow axis direction decrease gradually from the front cavity surface to the rear cavity surface.

[0013] Optionally, the spacing distance between the grating layer and the rear cavity surface is smaller than the spacing distance between the grating layer and the front cavity surface, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface to the grating layer but not to the rear cavity surface.

[0014] Optionally, the rear cavity surface is not provided with an anti-reflection film; or, the mode-regulated semiconductor light-emitting structure further includes: a first anti-reflection film located on the rear cavity surface.

[0015] Optionally, the spacing distance between the grating layer and the rear cavity surface is greater than the spacing distance between the grating layer and the front cavity surface, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the grating layer to the rear cavity surface but does not extend to the front cavity surface; the mode-regulated semiconductor light-emitting structure also includes: an anti-reflection film located on the rear cavity surface; a second anti-reflection film located on the front cavity surface; the reflectivity of the grating layer is less than the reflectivity of the rear cavity surface and greater than the reflectivity of the front cavity surface.

[0016] Optionally, the grating layer is located at least one of a first position, a second position, a third position, a fourth position, a fifth position, a sixth position, a seventh position and an eighth position; wherein the first position is between the first limiting layer and the first waveguide layer; the second position is between the first waveguide layer and the active layer; the third position is between the second waveguide layer and the active layer; the fourth position is between the second waveguide layer and the second limiting layer; the fifth position is in the first waveguide layer; the sixth position is in the second waveguide layer; the seventh position is in the first limiting layer; and the eighth position is in the second limiting layer.

[0017] Optionally, a size of the active layer in the slow axis direction is 10 μm to 1000 μm.

[0018] The present application also provides a method for preparing a mode-regulated semiconductor light-emitting structure, comprising: forming a first restriction layer, a first waveguide layer, an active layer, a second waveguide layer, and a second restriction layer stacked in sequence; forming a grating layer; wherein the grating layer is located between the first restriction layer and the active layer and / or between the second restriction layer and the active layer; the grating layer comprises: a plurality of grating strips arranged at intervals along the cavity length direction; at least a portion of the grating strips have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-regulated semiconductor light-emitting structure along the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction.

[0019] Optionally, the step of forming the grating layer includes: forming a grating material film; and patterning the grating material film so that the grating material film forms the grating layer.

[0020] The technical solution of this application has the following technical effects:

[0021] In the semiconductor light-emitting structure of the technical solution of the present application, the grating layer includes a plurality of grating strips arranged at intervals along the length of the cavity, and at least a portion of the grating strips have different lengths in the slow axis direction. The arrangement of grating strips with a larger length in the slow axis direction can improve the light output power of the mode-regulated semiconductor light-emitting structure. Secondly, by arranging grating strips with different lengths in the slow axis direction in the resonant cavity of the mode-regulated semiconductor light-emitting structure, the number of modes is reduced. Specifically, when the length of the grating strips in the slow axis direction is smaller, the reflection of the grating layer is concentrated in the central area of ​​the resonant cavity along the slow axis direction. This design guides the light in the resonant cavity to be mainly concentrated in the central area of ​​the resonant cavity along the slow axis direction, and the number of modes is reduced. At the same time, the effect of this mode-selective gain can suppress the reflection of higher-order modes, limit the gain of higher-order modes, make the lasing threshold of higher-order modes difficult to meet, and allow fundamental mode lasing. Since the number of modes is reduced, the spectral width is reduced. In summary, both the increase in light output power and the reduction in spectral width are taken into account. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 A schematic diagram of a mode-controlled semiconductor light-emitting structure according to an embodiment of the present application;

[0024] Figure 2 A top view of a grating layer in a mode-controlled semiconductor light-emitting structure according to an embodiment of the present application;

[0025] Figure 3 Another top view of a grating layer in a mode-controlled semiconductor light-emitting structure according to an embodiment of the present application;

[0026] Figure 4 A schematic diagram of the coupling coefficient of the grating layer and the mode field strength of the fundamental mode and the first-order mode in the slow axis direction in Test Example 1 of the present application;

[0027] Figure 5 is the equivalent coupling coefficient and g of the mode in test example 1 of this application th Schematic diagram of L changing with mode order;

[0028] Figure 6 Schematic diagram of the reflectivity of the grating layer in Test Example 2 of the present application, and the mode field intensity of the fundamental mode and the first-order mode in the slow axis direction;

[0029] Figure 7 Schematic diagram of the change of reflectivity of the mode in Test Example 2 of the present application with the mode order. DETAILED DESCRIPTION

[0030] Semiconductor lasers are developing rapidly, and their application fields are constantly expanding. High-power semiconductor lasers are generally used as pump sources, but the bandwidth of the ion absorption peak of the pump is generally relatively small. In order to meet market demand, high-power and narrow-spectrum semiconductor lasers are urgently needed. In the design of semiconductor lasers, in order to achieve a narrow and stable spectrum, a method is proposed to introduce a periodic grating element in the resonant cavity, and use the mode selection effect of the grating to reduce the spectral width of the semiconductor laser. At present, wide-strip distributed feedback (DFB) lasers are the mainstream solution. Wide-strip DFB lasers are widely used in fields such as pumping, spectral analysis, sensing, and medical high-power requirements due to their high power output. However, wide-strip DFB lasers face many challenges in achieving single-mode output and spectral purity, especially the multi-mode problem in the slow axis direction. In wide-strip DFB lasers, the power is increased due to the increase in the width of the gain zone in the slow axis direction, but the increased strip width will cause the laser to generate more heat when working, thereby exciting multiple modes, which seriously affects the output spectral width and cannot meet applications with high requirements for spectral purity and spectral stability. Therefore, it is very important to achieve high power while minimizing the spectral width in high-power wide-stripe DFB lasers.

[0031] On this basis, the embodiments of the present application propose a mode-regulated semiconductor light-emitting structure and a method for preparing the same, which take into account both improving the light output power and reducing the spectral width.

[0032] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0034] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] An embodiment of the present invention provides a mode-controlled semiconductor light-emitting structure, referring to Figure 1, including: a first confinement layer 120, a first waveguide layer 130, an active layer 140, a second waveguide layer 150 and a second confinement layer 170 stacked in sequence.

[0036] The mode-regulated semiconductor light-emitting structure further includes a grating layer, which is located between the first confinement layer 120 and the active layer 140 and / or between the second confinement layer 170 and the active layer 140 .

[0037] Figure 1 In the example, the grating layer 160 is located between the second confinement layer 170 and the active layer 140. In other embodiments, the grating layer may be located only between the first confinement layer 120 and the active layer 140. In other embodiments, the grating layer may be located between the first confinement layer 120 and the active layer 140 and between the second confinement layer 170 and the active layer 140.

[0038] refer to Figure 2 and Figure 3 The grating layer 160 includes a plurality of grating strips 161 arranged at intervals along the cavity length direction; at least a portion of the grating strips 161 have different lengths in the slow axis direction; the orthographic projection of the grating strips 161 along the cavity length direction on the front cavity surface Q1 of the mode-controlled semiconductor light-emitting structure intersects with the central axis of the front cavity surface Q1 in the fast axis direction.

[0039] In this embodiment, the grating layer 160 includes a plurality of grating strips 161 arranged at intervals along the length direction of the cavity, and at least a portion of the grating strips 161 have different lengths in the slow axis direction. The arrangement of the grating strips 161 with a larger length in the slow axis direction can improve the light output power of the mode-regulated semiconductor light-emitting structure. Secondly, by arranging the grating strips 161 with different lengths in the slow axis direction in the resonant cavity of the mode-regulated semiconductor light-emitting structure, the number of modes is reduced. Specifically, when the length of the grating strips 161 in the slow axis direction is smaller, the reflection of the grating layer 160 is concentrated in the central area of ​​the resonant cavity along the slow axis direction. This design guides the light in the resonant cavity to be mainly concentrated in the central area of ​​the resonant cavity along the slow axis direction, and the number of modes is reduced. At the same time, the effect of this mode selective gain can suppress the reflection of the high-order mode, limit the gain of the high-order mode, make the lasing threshold of the high-order mode difficult to meet, and allow the fundamental mode to be lasered. Since the number of modes is reduced, the spectral width is reduced. In summary, both the increase in light output power and the reduction in spectral width are taken into account.

[0040] In the related art, the number of modes of a semiconductor light emitting structure is affected by the size of the active layer in the slow axis direction. The larger the size of the active layer in the slow axis direction, the more modes it can accommodate, and the more likely it is to form a multi-mode phenomenon.

[0041] In the present application, by setting the grating strips 161 with smaller size in the slow axis direction, the distribution of the laser field in the slow axis direction can be limited. For the grating strips 161 with smaller size in the slow axis direction in the grating layer 160, the fundamental mode meets the constraint conditions of the grating strips 161, and the fundamental mode can obtain sufficient feedback and gain in the grating layer 160, thereby reaching the threshold of lasing. In contrast, other high-order modes are unstable due to the reflection and feedback of the grating strips 161 with smaller size in the slow axis direction, and the gain of other high-order modes is difficult to meet the threshold requirements.

[0042] The mode number of a higher-order mode is greater than or equal to 1. The mode number of a fundamental mode is 0.

[0043] When light propagates inside the mode-regulated semiconductor light-emitting structure, the distribution of the fundamental mode in the slow axis direction can stably adapt to the grating strips with smaller dimensions in the slow axis direction, and the area where the high-order modes are distributed in the slow axis direction is larger, so that the high-order modes cannot effectively form standing waves in the area where the grating strips with smaller dimensions in the slow axis direction are distributed, thereby reducing the number of modes in the resonant cavity. At the same time, the grating strips 161 with smaller dimensions in the slow axis direction enable the fundamental mode to obtain a higher reflectivity in the resonant cavity. This selective feedback of the reflectivity enhances the output stability of the fundamental mode. Therefore, by constraining the size of the grating strips 161 in the slow axis direction, the mode-regulated semiconductor light-emitting structure can filter out high-order modes and reduce the spectral width.

[0044] In this application, the thermal effect caused by multi-mode lasing is reduced, and the service life of the device is extended. The mode-controlled semiconductor light-emitting structure of the present invention is suitable for a variety of high-power application scenarios and meets the market demand for high-power narrow-spectrum lasers. This innovative design provides an effective solution for high-power, narrow-spectrum semiconductor lasers.

[0045] In one embodiment, the active layer 140 has a size of 10 μm to 1000 μm in the slow axis direction, such as 10 μm, 50 μm, 100 μm, 150 μm, 200 μm, 300 μm, 400 μm, 500 μm, 600 μm, 700 μm, 800 μm or 1000 μm. Since the active layer 140 has a larger size in the slow axis direction, the light output power of the mode-controlled semiconductor light-emitting structure can be increased.

[0046] In other embodiments, there is no limitation on the size of the active layer 140 in the slow axis direction.

[0047] In one embodiment, the length of the grating strip 161 with the smallest length in the slow axis direction among the plurality of grating strips 161 is 2 μm to 10 μm, for example, 2 μm, 4 μm, 6 μm, 8 μm or 10 μm.

[0048] In one embodiment, the length of the grating strip 161 with the longest length in the slow axis direction among the plurality of grating strips 161 is 80% to 100% of the size of the active layer 140 in the slow axis direction, for example, 80%, 90% or 100%.

[0049] In one embodiment, reference Figure 2 The grating layer 160 includes a plurality of grating groups A arranged in the cavity length direction, each grating group A includes a plurality of grating strips 161 arranged at intervals along the cavity length direction, and at least a portion of the grating strips 161 in the grating group A have different lengths in the slow axis direction. Figure 2 In the figure, a part of the grating strips 161 in the grating group A have different lengths in the slow axis direction.

[0050] In other embodiments, the lengths of all the grating strips in the grating group in the slow axis direction may be different.

[0051] The plurality of grating groups A include a first grating group to an Mth grating group arranged in the cavity length direction, where M is an integer greater than or equal to 2. Figure 2 In the example, M is greater than or equal to 4. Figure 2 The plurality of grating groups A include a first grating group A1 and a second grating group A2, and a third grating group A3 to an Mth grating group arranged in the cavity length direction. In other embodiments, M may also be an integer equal to 3 or greater than or equal to 5.

[0052] The mode-regulated semiconductor light-emitting structure comprises a front cavity surface Q1 and a rear cavity surface Q2 which are arranged opposite to each other in the cavity length direction.

[0053] In one embodiment, reference Figure 2 The length of the slow axis direction of the multiple grating strips 161 in the grating group A increases first and then decreases from the front cavity surface Q1 to the rear cavity surface Q2. The advantage is that the grating layer can selectively provide stronger feedback to the fundamental mode, while suppressing the gain of the high-order mode, making it difficult for the high-order mode to be excited, and guiding the light field to concentrate in the center of the cavity, thereby achieving a better balance between power and mode number.

[0054] In other embodiments, the lengths of the multiple grating strips in the grating group in the slow axis direction increase from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating strips in the grating group in the slow axis direction decrease from the front cavity surface to the rear cavity surface.

[0055] In one embodiment, the depths of the grating strips in the first grating group to the M-1 grating group in the fast axis direction are respectively less than the depths of the grating strips in the M grating group in the fast axis direction, and the resonant cavity of the mode-controlled semiconductor light-emitting structure extends from the front cavity surface Q1 to the M grating group and does not extend to the rear cavity surface Q2. Further, the depth of the grating strips in the M grating group in the fast axis direction is greater than or equal to 750nm, and the depth of the grating strips in the first grating group to the M-1 grating group in the fast axis direction is less than or equal to 700nm.

[0056] In one embodiment, when the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface Q1 to the Mth grating group and does not extend to the back cavity surface Q2, the back cavity surface Q2 is not provided with an anti-reflection film; or, the mode-regulated semiconductor light-emitting structure further includes: a first anti-reflection film located on the back cavity surface. Further, the reflectivity of the back cavity surface of the mode-regulated semiconductor light-emitting structure is lower than 1 / 3 of the maximum reflectivity of the grating layer in the slow axis direction.

[0057] In another embodiment, the plurality of grating groups include a first grating group to an Mth grating group, where M is an integer greater than or equal to 2. The resonant cavity of the mode-controlled semiconductor light-emitting structure extends from the front cavity surface Q1 to the rear cavity surface Q2. In this case, the depths of the grating strips in the first grating group to the Mth grating group in the fast axis direction are the same; or, the depths of the grating strips in the first grating group to the Mth grating group in the fast axis direction are at least partially different. Exemplarily, the depth of the grating strips in the fast axis direction is less than or equal to 700nm.

[0058] In one embodiment, the length of the multiple grating strips in the grating layer in the slow axis direction increases first and then decreases from the front cavity surface to the rear cavity surface; or, the length of the multiple grating strips in the grating layer in the slow axis direction increases gradually from the front cavity surface to the rear cavity surface; or, the length of the multiple grating strips in the grating layer in the slow axis direction decreases gradually from the front cavity surface to the rear cavity surface. Figure 3 It is taken as an example that the lengths of the plurality of grating strips 161 in the grating layer 160 in the slow axis direction decrease gradually from the front cavity surface Q1 to the rear cavity surface Q2.

[0059] In one embodiment, the distance between the grating layer 160 and the rear cavity surface Q2 is smaller than the distance between the grating layer 160 and the front cavity surface Q1. Figure 3 The spacing distance between the grating layer 160 and the rear cavity surface Q2 is smaller than the distance between the grating layer 160 and the front cavity surface Q1, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface Q1 to the grating layer 160 and does not extend to the rear cavity surface Q2.

[0060] In one embodiment, when the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface Q1 to the grating layer 160 and does not extend to the back cavity surface Q2, the back cavity surface Q2 is not provided with an anti-reflection film; or, the mode-regulated semiconductor light-emitting structure further includes: a first anti-reflection film located on the back cavity surface. Further, the reflectivity of the back cavity surface of the mode-regulated semiconductor light-emitting structure is lower than 1 / 3 of the maximum reflectivity of the grating layer in the slow axis direction.

[0061] In one embodiment, the spacing distance between the grating layer and the rear cavity surface is greater than the spacing distance between the grating layer and the front cavity surface, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the grating layer to the rear cavity surface but does not extend to the front cavity surface; the mode-regulated semiconductor light-emitting structure further includes: an anti-reflection film located on the rear cavity surface; and a second anti-reflection film located on the front cavity surface. The reflectivity of the grating layer is less than the reflectivity of the rear cavity surface and greater than the reflectivity of the front cavity surface. Furthermore, the reflectivity of the front cavity surface of the mode-regulated semiconductor light-emitting structure is lower than 1 / 3 of the maximum reflectivity of the grating layer in the slow axis direction.

[0062] In one embodiment, the grating layer is located at least one of a first position, a second position, a third position, a fourth position, a fifth position, a sixth position, a seventh position and an eighth position; wherein the first position is between the first limiting layer and the first waveguide layer; the second position is between the first waveguide layer and the active layer; the third position is between the second waveguide layer and the active layer; the fourth position is between the second waveguide layer and the second limiting layer; the fifth position is in the first waveguide layer; the sixth position is in the second waveguide layer; the seventh position is in the first limiting layer; and the eighth position is in the second limiting layer. Figure 1 This is just an example of the location of the grating layer 160 .

[0063] The grating layers are arranged symmetrically in the slow axis direction, or the grating layers are asymmetrical in the slow axis direction.

[0064] Test Example 1: The mode-controlled semiconductor light-emitting structure is a DBR (distributed Bragg reflector) laser, the width of the active layer in the slow axis direction is 100um, the cavity length of the mode-controlled semiconductor light-emitting structure is 3mm, the central wavelength of the mode-controlled semiconductor light-emitting structure is 980nm, and the mode-controlled semiconductor light-emitting structure includes a stacked first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, a second confinement layer, and a grating layer; the first confinement layer and the second confinement layer are AlGaAs confinement layers, the active layer includes a lnGaAs quantum well, and the first waveguide layer and the second waveguide layer are AlGaAs waveguide layers. Anti-reflection films are set on the front and rear cavity surfaces of the mode-controlled semiconductor light-emitting structure, and the reflectivity of the anti-reflection films is less than 0.1%; the period Λ of the grating layer is about 300nm. The first to 1110th grating groups are arranged in the cavity length direction, M=1110, and any grating group includes 17 grating strips. The length of the multiple grating strips in each grating group in the slow axis direction increases first and then decreases from the front cavity surface to the rear cavity surface; the size of the first grating strip in the grating group in the slow axis direction is 10μm, the size of the ninth grating strip in the grating group in the slow axis direction is 100μm, and the size of the seventeenth grating strip in the grating group in the slow axis direction is 10μm. The reflectivity of the grating layer is divided into 9 regions along the slow axis direction. For simplicity, the grating layer is centrally symmetric in the slow axis direction. The reflectivity of each grating group in different regions in the slow axis direction is related to the number of grating strips in the region, which can be obtained by Get the coupling coefficient of the grating layer , where L' is the size of a grating group along the cavity length direction, and r is the distribution of the reflectivity of the grating layer along the slow axis direction.

[0065] The coupling coefficient of the grating layer in Test Example 1, and the mode field strength of the fundamental mode and the first-order mode in the slow axis direction are shown in the figure below: Figure 4 shown. Figure 4 The horizontal axis represents the position of the slow axis direction, and the unit of the horizontal axis is micrometer. Figure 4 The left vertical axis is the coupling coefficient of the grating layer. Figure 4 The vertical axis on the right is the mode field intensity. Figure 4 L1 in the figure is the curve of the coupling coefficient of the grating layer changing with the position along the slow axis. Figure 4 L2 is a curve showing the change of the mode field intensity of the fundamental mode with the position along the slow axis. Figure 4 L3 in is a curve showing the change of the first-order mode field intensity with the position in the slow axis direction. In the mode-controlled semiconductor light-emitting structure, the low-order mode is concentrated in the center of the slow axis direction, and the high-order mode is dispersed in the position far from the center in the slow axis direction. Figure 4It can be seen that the grating layer of test example 1 highly reflects the position where the low-order mode field intensity distribution is strong, and the grating layer lowly reflects the position where the high-order mode field intensity distribution is weak.

[0066] By using the mode field integral overlap method, the overlap integral of the mode field and coupling coefficient of different modes in the slow axis direction is calculated to obtain the equivalent coupling coefficient of each order mode. The formula is as follows: ,in, is the mode field distribution of the m-order mode, is the position coordinate along the slow axis, is the equivalent coupling coefficient of the m-order mode, and m is the mode order. Based on the equivalent coupling coefficient of each order mode, the equivalent coupling coefficient and threshold gain g under different order modes can be obtained: th , / L, L is the size of the grating layer in the cavity length direction.

[0067] Figure 5 is the equivalent coupling coefficient of the mode in test case 1 and g th Schematic diagram of L changing with mode order, Figure 5 The horizontal axis is the mode order, Figure 5 The vertical axis on the left is the equivalent coupling coefficient of the mode, Figure 5 The vertical axis on the right is g th L, Figure 5 L8 in g th The curve of L changing with the mode order, Figure 5 L9 in is the curve of the equivalent coupling coefficient of the mode changing with the mode order. Figure 5 It can be seen that Test Example 1 effectively reduces the sum of the coupling coefficients of the high-order modes, suppresses the lasing of the high-order side modes, and thus reduces the number of lasing modes and the spectral width.

[0068] Test Example 2: The mode-controlled semiconductor light-emitting structure is a DBR laser, the width of the active layer in the slow axis direction is 100um, the cavity length of the mode-controlled semiconductor light-emitting structure is 3mm, the central wavelength of the mode-controlled semiconductor light-emitting structure is 980nm, and the mode-controlled semiconductor light-emitting structure includes a stacked first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, and a second confinement layer, and a grating layer; the first confinement layer and the second confinement layer are AlGaAs confinement layers, the active layer includes a lnGaAs quantum well, and the first waveguide layer and the second waveguide layer are AlGaAs waveguide layers. The period of the grating layer is about 300nm. The size of the grating layer in the cavity length direction is 200μm, and the number N of multiple grating strips in the grating layer is equal to 667. The spacing distance between the grating layer and the rear cavity surface is less than the spacing distance between the grating layer and the front cavity surface. The length of the multiple grating strips in the grating layer in the slow axis direction increases first and then decreases from the front cavity surface to the rear cavity surface. For simplicity, the grating layer is centrally symmetrical in the slow axis direction. The grating layer is equally divided into 2N-1 regions in the slow axis direction. The reflectivity of the grating layer of Test Example 2 and the mode field intensity of the fundamental mode and the first-order mode in the slow axis direction are shown in the figure below: Figure 6 shown. Figure 6 The horizontal axis represents the position of the slow axis direction, and the unit of the horizontal axis is micrometer. Figure 6 The left vertical axis is the reflectivity of the grating layer. Figure 6 The vertical axis on the right is the mode field intensity. Figure 6 L5 in is the curve of the reflectivity of the grating layer changing with the position along the slow axis. Figure 6 L6 in the figure is the curve of the fundamental mode's mode field intensity changing with the position of the slow axis direction. Figure 6 L7 is a curve showing the change of the mode field intensity of the first-order mode with the position along the slow axis.

[0069] Similarly, the reflectivity of each order mode of Test Example 2 is calculated by the mode field integral overlap method, which effectively reduces the reflectivity of the high-order mode. Figure 7 Schematic diagram of the change of reflectivity of each mode of test example 2 with the mode order. Figure 7 The horizontal axis in is the mode order, Figure 7 The vertical axis is the reflectivity of each order mode.

[0070] Another embodiment of the present application also provides a method for preparing a mode-regulated semiconductor light-emitting structure, comprising: forming a first restriction layer, a first waveguide layer, an active layer, a second waveguide layer, and a second restriction layer stacked in sequence; forming a grating layer; wherein the grating layer is located between the first restriction layer and the active layer and / or between the second restriction layer and the active layer; the grating layer comprises: a plurality of grating strips arranged at intervals along the cavity length direction; at least a portion of the grating strips have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-regulated semiconductor light-emitting structure along the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction.

[0071] The step of forming the grating layer includes: forming a grating material film; patterning the grating material film so that the grating material film forms the grating layer. The process of patterning the grating material film includes an electron beam etching process.

[0072] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A mode-controlled semiconductor light-emitting structure, characterized in that: include: A first confinement layer, a first waveguide layer, an active layer, a second waveguide layer and a second confinement layer stacked in sequence; a grating layer, located between the first confinement layer and the active layer and / or between the second confinement layer and the active layer; The grating layer comprises: the grating layer comprises a plurality of grating groups arranged in the cavity length direction, each grating group comprises a plurality of grating strips arranged at intervals in the cavity length direction; at least a portion of the grating strips in each grating group have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-controlled semiconductor light-emitting structure in the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction; The plurality of grating groups include a first grating group to an M-th grating group, where M is an integer greater than or equal to 2; wherein the depths of the grating bars in the first grating group to the M-1-th grating group in the fast axis direction are respectively less than the depths of the grating bars in the M-th grating group in the fast axis direction, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface to the M-th grating group and does not extend to the rear cavity surface; The rear cavity surface is not provided with an anti-reflection film; or, the mode-regulated semiconductor light-emitting structure further includes: a first anti-reflection film located on the rear cavity surface.

2. The mode-controlled semiconductor light-emitting structure according to claim 1, characterized in that: The length of the grating strip with the shortest length in the slow axis direction among the plurality of grating strips is 2 μm to 10 μm.

3. The mode-controlled semiconductor light-emitting structure according to claim 1, characterized in that: The length of the grating strip with the longest length in the slow axis direction among the plurality of grating strips is 80% to 100% of the size of the active layer in the slow axis direction.

4. The mode-controlled semiconductor light-emitting structure according to claim 1, characterized in that: The lengths of the multiple grating strips in the grating group in the slow axis direction first increase and then decrease from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating strips in the grating group in the slow axis direction increase gradually from the front cavity surface to the rear cavity surface; or, the lengths of the multiple grating strips in the grating group in the slow axis direction decrease gradually from the front cavity surface to the rear cavity surface.

5. The mode-controlled semiconductor light-emitting structure according to claim 1, characterized in that: The grating layer is located at least one of a first position, a second position, a third position, a fourth position, a fifth position, a sixth position, a seventh position and an eighth position; Among them, the first position is between the first restriction layer and the first waveguide layer; the second position is between the first waveguide layer and the active layer; the third position is between the second waveguide layer and the active layer; the fourth position is between the second waveguide layer and the second restriction layer; the fifth position is in the first waveguide layer; the sixth position is in the second waveguide layer; the seventh position is in the first restriction layer; and the eighth position is in the second restriction layer.

6. The mode-controlled semiconductor light-emitting structure according to claim 1, characterized in that: The size of the active layer in the slow axis direction is 10 μm to 1000 μm.

7. A method for preparing a mode-controlled semiconductor light-emitting structure, characterized in that: include: forming a first confinement layer, a first waveguide layer, an active layer, a second waveguide layer, and a second confinement layer stacked in sequence; forming a grating layer; The grating layer is located between the first limiting layer and the active layer and / or between the second limiting layer and the active layer; the grating layer comprises: a plurality of grating groups arranged in the cavity length direction, each grating group comprises a plurality of grating strips arranged at intervals in the cavity length direction; at least a part of the grating strips in each grating group have different lengths in the slow axis direction; the orthographic projection of the grating strips on the front cavity surface of the mode-controlled semiconductor light-emitting structure in the cavity length direction intersects with the central axis of the front cavity surface in the fast axis direction; The plurality of grating groups include a first grating group to an M-th grating group, where M is an integer greater than or equal to 2; wherein the depths of the grating bars in the first grating group to the M-1-th grating group in the fast axis direction are respectively less than the depths of the grating bars in the M-th grating group in the fast axis direction, and the resonant cavity of the mode-regulated semiconductor light-emitting structure extends from the front cavity surface to the M-th grating group and does not extend to the rear cavity surface; The rear cavity surface is not provided with an anti-reflection film; or, the mode-regulated semiconductor light-emitting structure further includes: a first anti-reflection film located on the rear cavity surface.

8. The method for preparing a mode-controlled semiconductor light-emitting structure according to claim 7, characterized in that: The step of forming the grating layer comprises: forming a grating material film; The grating material film is patterned so that the grating material film forms the grating layer.

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