Vertical Cavity Surface Emitting Laser

Abstract

To provide a vertical resonator surface emission laser which has a simple structure, can be easily manufactured, with a low cost.SOLUTION: A vertical resonator surface emission laser comprises: a substrate layer 11 arranged so as to be laminated; a buffer layer 12; a first reflector layer 13; a light emission layer 14; a polarization selective hybrid layer 15; and an electrode layer 16. The polarization selective hybrid layer includes: a second reflector layer 151; and a near wavelength grating layer 152 that is integrated above the second reflector layer. A period of a near wavelength grating is smaller than a wavelength in a propagation medium, and is larger than the wavelength of light in a semiconductor material of the vertical resonator surface emission laser.EFFECT: Use of the vertical resonator surface emission laser of the present disclosure can be emit highly stable and highly polarized laser light, with a simple structure capable of being easily manufactured, making the second reflector layer thinner, and reducing a production cost.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates generally to the technical field of optoelectronic devices, and more particularly to vertical cavity surface emitting lasers. [Background technology]

[0002] Vertical Cavity Surface Emitting Lasers (VCSELs) have many advantages, such as small volume, long service life, and low threshold current, and can be widely applied in fields such as high-speed optical chips, data centers, structured light, and laser radar.

[0003] The laser emission of conventional VCSELs shows different degrees of polarization depending on the device design, fabrication conditions, and highly complicated modes of spontaneous polarization conversion under various operating conditions. Currently, the related art uses diffraction gratings, sub-wavelength gratings, etc. to show VCSELs with stable polarization, but these configurations each have certain drawbacks. For example, a diffraction grating with a period larger than the laser wavelength has a large feature size and is easy to fabricate, but its performance is significantly degraded due to high-order diffraction losses. Moreover, for example, a sub-wavelength grating requires a period smaller than the laser wavelength and a special epitaxy method to form it, which brings great challenges to fabrication and increases production costs. Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above-mentioned deficiencies and shortcomings in the related art, it is an object of the present invention to provide a vertical cavity surface emitting laser that is simple in structure, easy to manufacture, and inexpensive. [Means for solving the problem]

[0005] The present disclosure provides a vertical cavity surface emitting laser comprising a substrate layer, a buffer layer, a first reflector layer, a light emitting layer, a polarization selective mixed layer, and an electrode layer arranged in a stacked manner, the polarization selective mixed layer including a second reflector layer and a near-wavelength grating layer integrated above the second reflector layer, wherein a period of the near-wavelength grating is smaller than a wavelength of light in a propagation medium and larger than a wavelength of light in a semiconductor material of the vertical cavity surface emitting laser.

[0006] Alternatively, in some embodiments of the present disclosure, the near wavelength grating is formed by etching a cap layer in the second reflector layer.

[0007] Alternatively, in some embodiments of the present disclosure, the shape of the near wavelength grating corresponding region includes at least one of a polygon and a circle.

[0008] Alternatively, in some embodiments of the present disclosure, the outer surface of the near wavelength grating is provided with at least one conformal layer.

[0009] Alternatively, in some embodiments of the present disclosure, when the cumulative thickness of the conformal layer exceeds a predetermined threshold, a planarization layer is further provided above the conformal layer, and an air gap exists between the planarization layer and the conformal layer.

[0010] Alternatively, in some embodiments of the present disclosure, the conformal layer and the planarization layer are a SiN layer and an AlN layer, respectively. 2 O 3 layer, TiO 2 layer, SiO 2 At least one of the layers.

[0011] Alternatively, in some embodiments of the present disclosure, at least one stop layer is provided below the near wavelength grating.

[0012] Alternatively, in some embodiments of the present disclosure, the bottom of the near-wavelength grating is located above the stop layer, or the bottom of the near-wavelength grating penetrates the stop layer and into a cap layer in the second reflector layer.

[0013] Alternatively, in some embodiments of the present disclosure, the stop layer comprises at least one of a Si layer, a Ge layer, a GaN layer, an AlGaN layer, a GaAs layer, an AlGaAs layer, an InGaP layer, an InGaAs layer, and an AlAs layer.

[0014] Alternatively, in some embodiments of the present disclosure, the light emitting layer comprises an active layer and an oxide layer arranged in a stacked manner, the oxide layer including a non-oxidized region for emitting laser light and an oxidized region surrounding the non-oxidized region. Effect of the Invention

[0015] As can be seen from the above technical solution, the embodiments of the present disclosure have the following advantages: An embodiment of the present disclosure provides a vertical cavity surface emitting laser, which integrates a near-wavelength grating layer and a second reflector layer, in which the period of the near-wavelength grating is smaller than the wavelength of light in the propagation medium and larger than the wavelength of light in the semiconductor material of the laser, thereby forming a polarization selective mixed layer of the laser cavity, which can emit highly stable and highly polarized laser light, and has a simple structure and easy fabrication, as well as a thinner second reflector layer, reducing the production cost.

[0016] Other features, objects and advantages of the present disclosure will become more apparent upon reference to the following detailed description of non-limiting embodiments in the drawings, in which: [Brief description of the drawings]

[0017] [Figure 1] 1 is a schematic diagram of the structure of a vertical cavity surface emitting laser according to an embodiment of the present disclosure. [Diagram 2] FIG. 1 is a schematic diagram of reflectivity, diffraction loss, and phase obtained by RCWA calculation according to an embodiment of the present disclosure. [Diagram 3] 1A-1C are schematic diagrams showing one conformal layer, two conformal layers, and multiple conformal layers provided according to embodiments of the present disclosure. [Figure 4] FIG. 2 is another schematic diagram of a multiple conformal layer provided according to an embodiment of the present disclosure. [Diagram 5] FIG. 2 is another schematic diagram of a multiple conformal layer provided according to an embodiment of the present disclosure. [Figure 6] 1A-1C are schematic diagrams illustrating one stop layer, two stop layers, and multiple stop layers according to embodiments of the present disclosure. [Figure 7] FIG. 2 is a schematic diagram of the positional relationship between a near wavelength grating and a stop layer according to an embodiment of the present disclosure. [Figure 8] FIG. 2 is another schematic diagram of the positional relationship between a near wavelength grating and a stop layer according to an embodiment of the present disclosure. [Figure 9] FIG. 2 is a schematic diagram of the relationship between the size of the near-wavelength grating corresponding region and the size of the non-oxidized region according to an embodiment of the present disclosure. [Figure 10] FIG. 13 is another schematic diagram of the relationship between the size of the near-wavelength grating corresponding region and the size of the non-oxidized region according to an embodiment of the present disclosure. [Figure 11] FIG. 13 is another schematic diagram of the relationship between the size of the near-wavelength grating corresponding region and the size of the non-oxidized region according to an embodiment of the present disclosure. [Figure 12] 1A-1C are schematic diagrams of different shapes of grating regions according to embodiments of the present disclosure. [Figure 13] 1A-1C are schematic diagrams of different orientations of grating elements according to embodiments of the present disclosure. [Figure 14] FIG. 2 is a schematic diagram of a lattice grid according to an embodiment of the present disclosure. [Figure 15] FIG. 2 is a schematic diagram of a cell of a lattice according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In order to allow those skilled in the art to better understand the means of the present disclosure, the technical solutions of the embodiments of the present disclosure are described below clearly and completely with reference to the drawings of the embodiments of the present disclosure, obviously, the described embodiments are only some of the embodiments of the present disclosure, not all of the embodiments, other embodiments that those skilled in the art can obtain without creative labor based on the embodiments of the present disclosure all belong to the protection scope of the present disclosure.

[0019] The terms "first," "second," "third," "fourth," etc. (if any) in the specification, claims, and drawings of this disclosure are intended to distinguish between similar objects and are not necessarily used to describe a particular order or chronology. It should be understood that the data so used can be interchanged where appropriate such that the embodiments of the present disclosure described may be implemented in orders other than those shown or described herein.

[0020] Additionally, the terms "including" and "comprises," as well as any variations thereof, are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or apparatus that includes a series of steps or modules is not necessarily limited to those steps or modules expressly recited, but may include other steps or modules that are not expressly recited or that are inherent to the process, method, product, or apparatus.

[0021] For ease of understanding and description, vertical cavity surface emitting lasers according to embodiments of the present disclosure will be described in detail below through FIGS.

[0022] As shown in FIG. 1, FIG. 1 is a structural schematic diagram of a vertical cavity surface emitting laser according to an embodiment of the present disclosure. The vertical cavity surface emitting laser 10 includes a substrate layer 11, a buffer layer 12, a first reflector layer 13, a light emitting layer 14, a polarization selective mixed layer 15, and an electrode layer 16 arranged in a stacked manner, and the polarization selective mixed layer 15 includes a second reflector layer 151 and a near-wavelength grating layer 152 integrated above the second reflector layer 151, and the period of the near-wavelength grating is smaller than the wavelength of light in the propagation medium (e.g., air) and larger than the wavelength of light in the semiconductor material of the vertical cavity surface emitting laser 10. Thereby, any loss from higher diffraction orders in the transmission direction is completely eliminated, and the loss from higher diffraction orders in the reflection direction is minimized by appropriately designing the bar width, gap and etching depth of the grating.

[0023] Alternatively, in the embodiment of the present disclosure, the near-wavelength grating is formed by etching the cap layer 1511 in the second reflector layer 151. In this way, there is no need to modify the existing epitaxial design, and it has the advantages of ease of manufacture and that the vertical cavity surface emitting laser 10 can be manufactured side by side with a conventional vertical cavity surface emitting laser, and both types of devices can be integrated into an array. Also, the far field of the vertical cavity surface emitting laser 10 may be approximately similar to that of the conventional vertical cavity surface emitting laser.

[0024] In the embodiment of the present disclosure, the first reflector layer 13 and the second reflector layer 151 may be Distributed Bragg Reflector (DBR) layers. Furthermore, the hybrid reflector is designed such that the reflectance for light of the desired polarization direction matches the reflectance of an independent DBR, while the reflectance for light of a non-desired polarization direction is greater than a threshold and smaller than the reflectance for light of the desired polarization direction. The difference in reflectance of the polarization selective mixed layer 15 may be any value greater than 0.5, 0.8, 1, 1.5, 2, 3, 5, 10 or 20%, where the greater the difference in reflectance, the greater the degree of polarization of the laser light, and the more stable the degree of polarization of the laser light under various operating conditions such as different laser driving currents and different temperatures, and the degree of polarization of the laser light may be greater than 5 dB, 7 dB, 10 dB, 15 dB, 20 dB, or 30 dB. Also, the diffraction losses due to the near wavelength grating can be minimized by proper design and may be less than 50%, 30%, 20%, 15%, 10%, 7%, 5%, 3%, 2%, 1%, 0.5%. In summary, the advantage of integrating a near wavelength grating into a laser reflector is that the performance losses of the laser are at most only affected by the diffraction losses of the grating in the desired polarization direction of the laser, and conversely, the diffraction losses of light with polarization directions other than the desired one only have a small effect on the laser's performance.

[0025] As shown in FIG. 2, FIG. 2 is a schematic diagram of the reflectivity, diffraction loss, and phase obtained by RCWA (Rigorous Coupled Wave Analysis) calculation according to an embodiment of the present disclosure, where the desired polarization of the laser light is TE mode. For such polarization, the hybrid reflector is designed to have an enhanced reflectivity and to optimize the performance of the laser, such as power, threshold, and slope efficiency, while matching the reflectivity of the second reflector layer 151 in the absence of a near-wavelength grating. In TE mode, the polarization-selective mixed layer 15 has a designed low diffraction loss of less than 10%, which minimizes the impact on the performance of the laser. In TM mode, the diffraction loss of the light is between 20% and 25%, which is obviously higher than the TE mode, but since its reflectivity is lower than the TE mode and it is not excited, there is no real impact on the performance of the laser. For TE and TM light, the hybrid reflector has one-pass phases close to π and 0, respectively, which means that the light of the two polarization directions meets the round-trip phase condition of multiples of 2π. In summary, the total phase of the hybrid reflector is determined by the lattice parameters such as the thickness of the DBR layers, the design and period of the DBR cap layer 1511, the bar width, gap, and etch depth.

[0026] Alternatively, in the embodiment of the present disclosure, at least one conformal layer 153 is provided on the outer surface of the near-wavelength grating, thus advantageously improving the reliability and optical properties of the vertical cavity surface emitting laser 10. For example, as shown in FIG. 3, FIG. 3 is a schematic diagram of one conformal layer, two conformal layers, or multiple conformal layers according to the embodiment of the present disclosure, and when the cumulative thickness of the conformal layer 153 exceeds a predetermined threshold, the gap between the grating and the structure is flattened, and a flattening layer 154 is provided above the conformal layer 153, where the predetermined threshold may be 0.5 times the height of the gap of the grating. Furthermore, as shown in FIG. 4, FIG. 4 shows how the perfectly conformal conformal layer 153 is bonded along the interface 155 to reach flatness. As shown in FIG. 5, FIG. 5 shows how the conformal layer 153 is bonded along the interface 155 to form an air gap 156 after reaching flatness. It should be noted that in the embodiment of the present disclosure, the conformal layer 153 and the planarization layer 154 can be made of inorganic dielectric materials, such as a SiN layer and an AlN layer, respectively. 2 O 3 layer, TiO 2 layer, SiO 2 The thin-film transistor includes at least one of the layers and is formed by a method such as ALD (Atomic Layer Deposition), PECVD (Plasma Enhanced Chemical Vapor Deposition), CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), or sputtering.

[0027] Alternatively, in the embodiment of the present disclosure, at least one stop layer 157 is provided below the near-wavelength grating, which can be used for etching stop or propagation defect stop, thereby enhancing the uniformity of the grating etching depth, improving the cross-sectional shape of the grating gap, and also improving the accuracy of the grating gap etching depth, for example, the etching forming the grating gap has a selectivity above a threshold level of 1.5:1, 2:1, 3:1, 5:1, 10:1, 20:1, 50:1, 100:1, etc. with respect to the material of the stop layer 157 and the material of the cap layer 1511 of the second reflector layer 151, and the reliability of the vertical cavity surface emitting laser 10 is also improved. Here, the stop layer 157 and the cap layer 1511 of the second reflector layer 151 can be formed by methods such as MOCVD (Metal-organic Chemical Vapor Deposition), MBE (Molecular Beam Epitaxy) and LPE (Liquid Phase Epitaxy) during the epitaxial growth process of the structure of the vertical cavity surface emitting laser 10. For example, as shown in FIG. 6, FIG. 6 is a schematic diagram of one stop layer, two stop layers, or multiple stop layers according to an embodiment of the present disclosure. Furthermore, as shown in FIG. 7, the bottom of the near wavelength grating is located above the stop layer 157, or as shown in FIG. 8, the bottom of the near wavelength grating penetrates the stop layer 157 and reaches into the cap layer 1511 in the second reflector layer 151. It should be noted that in the embodiment of the present disclosure, the stop layer 157 may be made of a semiconductor material, such as at least one of a Si layer, a Ge layer, a GaN layer, an AlGaN layer, a GaAs layer, an AlGaAs layer, an InGaP layer, an InGaAs layer, and an AlAs layer. The refractive index of the stop layer 157 may be close to or closely matched to the refractive index of the material constituting the cap layer 1511 of the second reflector layer 151, and the stop layer 157 may have a thickness of less than λ / 4, λ / 6, λ / 8, λ / 10, or less than 50 nm, 20 nm, 10 nm, 7 nm, 5 nm, where λ represents the wavelength of the laser light.

[0028] Alternatively, in the embodiment of the present disclosure, the light emitting layer 14 comprises an active layer 141 and an oxide layer 142 arranged in a stacked manner, the oxide layer 142 includes a non-oxidized region 143 for emitting laser light and an oxide region 144 surrounding the non-oxidized region 143, for example, the oxide layer 142 may include an aluminum material, and the emitted laser light is in the near infrared range and has a polarization direction parallel to the near wavelength lattice bar. Here, the active layer 141 is a single quantum well layer or a multiple quantum well (MQW) layer, and is used to emit light when energized, the non-oxidized region 143 is a conductive region, and after a voltage is applied to the electrodes at both ends of the vertical cavity surface emitting laser 10, a current is conducted through the non-oxidized region 143, while the oxide region 144 is an insulating region, and is used to block the current.

[0029] Furthermore, as shown in FIG. 9, in the embodiment of the present disclosure, the size of the near-wavelength grating corresponding region may be larger than the size of the non-oxidized region 143, so that almost all the laser modes of the vertical cavity surface emitting laser 10 are polarized. As shown in FIG. 10, the size of the near-wavelength grating corresponding region may be equal to the size of the non-oxidized region 143, or as shown in FIG. 11, the size of the near-wavelength grating corresponding region may be smaller than the size of the non-oxidized region 143, in which case many laser light transverse modes of the vertical cavity surface emitting laser 10, such as the base mode, are polarized. Depending on the relative reflectivity of the region with the grating and the region without the grating of the hybrid reflector, if the reflectivity of the hybrid reflector is approximately equal to the reflectivity of the independent second reflector layer 151, several laser light transverse modes can be polarized, and some other modes may be unpolarized. If the reflectivity of the hybrid reflector is higher than the reflectivity of the independent second reflector layer 151, many polarized modes of the vertical cavity surface emitting laser 10 will emit laser light in preference to many unpolarized modes.

[0030] Alternatively, in the embodiment of the present disclosure, the shape of the near-wavelength grating corresponding region has at least one of a polygon and a circle, the polygon including but not limited to a triangle, a square, and the circle including but not limited to a perfect circle, an ellipse, and the like. For example, as shown in FIG. 12 and FIG. 13, the grating region of the hybrid reflector can be designed in various shapes and orientations so that a specific transverse mode of the vertical cavity surface emitting laser 10 is polarized. Depending on the relative reflectivity of the region with the grating and the region without the grating of the hybrid reflector, the vertical cavity surface emitting laser 10 preferably emits light of a specific polarized transverse mode, or light of a specific polarized transverse mode, or unpolarized light of another transverse mode. The shape and orientation of the grating portion of the hybrid reflector are designed so that the vertical cavity surface emitting laser 10 emits laser light with a desired polarization direction in a specific transverse mode, where the emission direction of linear polarization can be controlled by rotation, and the circular polarization can be controlled by a chiral structure.

[0031] Further, Fig. 14 and Fig. 15 are schematic diagrams of a grid and a cell of a grating according to an embodiment of the present disclosure, respectively. A 2D grating structure can be defined by the grid shown in Fig. 14 and can be combined with a specific grating element or a cell shown in Fig. 15. As can be seen, the asymmetric grating element is for designing a 2D grating-based hybrid reflector that is selective for linearly polarized light, and the chiral grating element is for designing a 2D grating-based hybrid reflector that is selective for circularly polarized light.

[0032] The vertical cavity surface emitting laser according to the embodiments of the present disclosure integrates a near-wavelength grating layer and a second reflector layer, in which the period of the near-wavelength grating is smaller than the wavelength of light in the propagation medium and larger than the wavelength of light in the semiconductor material of the laser, thereby forming a polarization selective mixed layer of the laser cavity, which can emit highly stable and highly polarized laser light, and has a simple structure and is easy to manufacture, as well as a thinner second reflector layer, which reduces the production cost.

[0033] It should be noted that the above examples are merely for the purpose of explaining the technical solutions of the present disclosure and are not intended to limit the same. The present disclosure has been described in detail with reference to the above examples. However, those skilled in the art can understand that the technical solutions described in the above examples may be modified or equivalent substitutions may be made to some of the technical features therein, and that such modifications and substitutions will not deviate from the essence of the corresponding technical solutions of the embodiments of the present disclosure. [Explanation of symbols]

[0034] 10, vertical cavity surface emitting laser 11, substrate layer 12, buffer layer 13, first reflector layer 14, light emitting layer 141, active layer 142, oxide layer 143, non-oxidized region 144, oxidized region 15, polarization selective mixing layer 151, second reflector layer 1511, cap layer 152, near wavelength grating layer 153, conformal layer 154, planarization layer 155, interface 156, gap 157, stop layer 16, electrode layer

Claims

1. 1. A vertical cavity surface emitting laser, comprising: The light emitting device includes a substrate layer, a buffer layer, a first reflector layer, a light emitting layer, a polarization selective mixing layer, and an electrode layer, which are stacked one on top of the other; The polarization selective mixed layer includes a second reflector layer, a cap layer formed above the second reflector layer, and a near-wavelength grating layer integrated with the cap layer and configured with a near-wavelength grating; the near wavelength grating is formed by etching a cap layer of the second reflector layer; A vertical cavity surface emitting laser, characterized in that the period of the near wavelength grating is smaller than the wavelength of light in a propagation medium and larger than the wavelength of light in a semiconductor material of the vertical cavity surface emitting laser.

2. 2. The vertical cavity surface emitting laser according to claim 1, wherein the shape of the near wavelength grating corresponding region includes at least one of a polygon and a circle.

3. 3. The vertical cavity surface emitting laser of claim 1, wherein an outer surface of the near wavelength grating is provided with at least one conformal layer.

4. 4. The vertical cavity surface emitting laser of claim 3, wherein when a cumulative thickness of the conformal layer exceeds a predetermined threshold, a planarization layer is further provided above the conformal layer, and an air gap exists between the planarization layer and the conformal layer.

5. The conformal layer and the planarization layer are a SiN layer and an Al ２ O ３ layer, TiO ２ layer, SiO ２ 5. The vertical cavity surface emitting laser of claim 4 including at least one layer.

6. 3. The vertical cavity surface emitting laser according to claim 1, further comprising at least one stop layer below said near wavelength grating.

7. 7. The vertical cavity surface emitting laser of claim 6, wherein the bottom of the near wavelength grating is located above the stop layer, or the bottom of the near wavelength grating penetrates the stop layer and reaches into a cap layer in the second reflector layer.

8. 7. The vertical cavity surface emitting laser of claim 6, wherein the stop layer comprises at least one of a Si layer, a Ge layer, a GaN layer, an AlGaN layer, a GaAs layer, an AlGaAs layer, an InGaP layer, an InGaAs layer, and an AlAs layer.

9. 2. The vertical cavity surface emitting laser according to claim 1, wherein the light emitting layer comprises an active layer and an oxide layer which are stacked together, the oxide layer including a non-oxidized region for emitting laser light and an oxidized region surrounding the non-oxidized region.

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