A vertical cavity surface emitting laser
By using nanoimprinted Fresnel lenses prepared in the light window of the VCSEL laser, the problems of excessive divergence angle and difficulty in focal length adjustment of the VCSEL laser are solved, and a smaller package volume and lower number of lasing modes are achieved.
Patent Information
- Application Number
- CN202421221362.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-30
- Publication Date
- 2025-04-11
- Estimated Expiration
- 2034-05-30
AI Technical Summary
The divergence angle of existing VCSEL lasers is too large, limiting its effect in long-distance applications. At the same time, the package size is large and the structure is easily damaged due to the inability to adjust the focal length of the light window.
The Fresnel lens is prepared by nanoimprinting at the light window of VCSEL. The Fresnel lens is located above the oxidation hole of the oxide layer, and the laser light exit angle and focus point are controlled by adjusting the diameter and number of turns of the lens.
It effectively reduces the divergence angle of the laser, reduces the package volume, and reduces the number of laser modes, solving the problem of difficulty in focal length adjustment.
Smart Images
Figure CN222749867U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of lasers, in particular to a vertical cavity surface emitting laser. Background Art
[0002] The inherent structure of VCSEL (Vertical-Cavity Surface-Emitting Laser, VCSEL for short) has limited lateral and vertical restrictions on the laser spot, resulting in a large divergence angle of the device, which limits the long-distance application of VCSEL.
[0003] Currently, VCSELs made using an oxidation process generally have a larger divergence angle. The divergence angle can be adjusted by controlling the size of the oxidation hole diameter. For example, reducing the diameter of the oxidation hole from 10um to 3um can effectively reduce the divergence angle of the VCSEL. However, reducing the diameter of the oxidation hole will cause the laser current density to be too high and limit the maximum output power, thereby causing the laser to fail.
[0004] Since the optical window of VCSEL is a plane mirror and the focal length cannot be adjusted, concave or convex lenses are usually made of polymer materials and integrated on the substrate for light type control. This method has a large volume after packaging and is not easy to install. The stress between the lens and the epitaxial layer can cause damage to the internal structure of the laser. There is also a wet etching method to micro-etch the optical window position to reduce the divergence angle, but since the etching pattern is generally circular and only the optical window is micro-processed in the vertical direction of the surface, the improvement effect is limited. Utility Model Content
[0005] The technical problem to be solved by the utility model is to provide a vertical cavity surface emitting laser and control the light emitting angle and focusing point of the laser.
[0006] In order to solve the above technical problems, the technical solution of the utility model is:
[0007] A vertical cavity surface emitting laser comprises a first DBR layer, an active layer, an oxide layer and a second DBR layer which are sequentially stacked on a substrate. A Fresnel lens is formed on a surface of the second DBR layer away from the substrate. The Fresnel lens is located above an oxide hole in the oxide layer.
[0008] Furthermore, the diameter of the Fresnel lens is larger than the aperture of the oxidation hole.
[0009] Furthermore, the center of the Fresnel lens and the center of the oxidation hole are on the same straight line.
[0010] Furthermore, the diameter of the Fresnel lens is 8-10 μm.
[0011] Furthermore, the pore size of the oxidation pores is 5-8 μm.
[0012] Furthermore, the number of circles of the Fresnel lens is 20-50, and the width of each prism of the Fresnel lens is 150-500 nm.
[0013] Furthermore, it also includes a first electrode and a second electrode, wherein the first electrode is located on the substrate, and the second electrode is located on the second DBR layer.
[0014] Furthermore, the material of the substrate is N-type gallium arsenide, the material of the first DBR layer is N-type aluminum gallium arsenide, and the material of the active region is The material of the second DBR layer is P-type AlGaAs, and the material of the first electrode is gold-germanium alloy or palladium Gold, and the second electrode is titanium platinum.
[0015] Furthermore, a Fresnel lens prepared by ultraviolet nanoimprinting is formed on the surface of the second DBR layer away from the substrate.
[0016] A vertical cavity surface emitting laser is used in mobile phones, sweeping robots or optical communications.
[0017] After adopting the above scheme, since the utility model uses nanoimprinting to prepare the Fresnel lens on the optical window of the laser, and since it is processed in the epitaxial layer, compared with the external package convex lens or concave lens, the process can reduce the volume of the laser after packaging, and can also filter the lasing mode and reduce the number of lasing modes. It solves the problems of the current VCSEL that the divergence angle is too large, the lasing modes are too many, and the focal length cannot be adjusted at the application end. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 It is a structural schematic diagram of the utility model;
[0019] Figure 2 It is a schematic diagram of relevant parameters of the Fresnel lens of the utility model.
[0020] Description of symbols
[0021] Substrate 1 First DBR layer 2 Active layer 3 Oxide layer 4
[0022] Second DBR layer 5 Fresnel lens 51 First electrode 61 Second electrode 62 DETAILED DESCRIPTION
[0023] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that if the terms "upper", "lower", "inner", "outer" and other positions or positional relationships are based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use, they are only for the convenience of description and cannot be understood as limitations on the present invention. The technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.
[0024] like Figure 1 As shown, a vertical cavity surface emitting laser includes a first DBR layer 2, an active layer 3, an oxide layer 4 and a second DBR layer 5 which are sequentially stacked on a substrate 1, and a Fresnel lens 51 is formed on a surface of the second DBR layer 5 away from the substrate 1, and the Fresnel lens 51 is located above the oxide hole of the oxide layer 4.
[0025] The first electrode 61 and the second electrode 62 are also included. The first electrode 61 is located on the substrate 1 , and the second electrode 62 is located on the second DBR layer 5 .
[0026] A Fresnel lens 51 prepared by ultraviolet nanoimprinting is formed on the surface of the second DBR layer 5, that is, the Fresnel lens 51 is located on the surface of the second DBR layer 5 away from the substrate 1. Compared with the prior art, the convex lens or concave lens in the laser chip integrated package is used to adjust the beam, which can greatly reduce the volume of the integrated package.
[0027] Furthermore, the diameter of the Fresnel lens 51 is larger than the aperture of the oxidation hole 4. Figure 1 As shown, the diameter of the Fresnel lens 51 is D, and the aperture of the oxidation hole 4 is C, that is, D ≥ C. If the aperture of the oxidation hole 4 is larger than the diameter of the Fresnel lens 51, a portion of the light cannot be refracted and focused and is lost, which will affect the performance of the device. In order to obtain the best effect, under the condition that the diameter of the Fresnel lens 51 is larger than the aperture of the oxidation hole 4, the center of the Fresnel lens 51 and the center of the oxidation hole 4 are on the same straight line.
[0028] In this embodiment, the diameter of the oxidation holes of the oxidation layer 4 is 5-8 μm. According to the size of the optical window of the VCSEL laser, the diameter of the Fresnel lens 51 is 8-10 μm. The distance between the outermost circle of the Fresnel lens 51 and the second electrode 62 is 1-2 μm.
[0029] The larger the number of turns of the Fresnel lens 51 is, the higher the process difficulty and requirements are. In the present embodiment, the number of turns of the Fresnel lens 51 is 20-50 turns. If the number of turns is too small, the focusing effect cannot be achieved, which affects the device performance.
[0030] Furthermore, the width of each prism of the Fresnel lens 51 is 150-500 nm.
[0031] Further, the material of the substrate 1 is N-type gallium arsenide, the material of the first DBR layer 2 is N-type aluminum gallium arsenide, the material of the active region 3 is indium gallium arsenide or aluminum gallium arsenide, the material of the second DBR layer 5 is P-type aluminum gallium arsenide, the material of the first electrode 61 is gold germanium alloy or palladium gold, and the material of the second electrode 62 is titanium platinum gold. The above materials are all known material names and are existing materials that can be directly purchased from the market.
[0032] Embodiment 1: A vertical cavity surface emitting laser comprises a first DBR layer 2, an active layer 3, an oxide layer 4, and a second DBR layer 5 stacked on a substrate 1 in sequence, a Fresnel lens 51 is formed on the surface of the second DBR layer 5 away from the substrate 1, and the Fresnel lens 51 is located above the oxide hole of the oxide layer 4, the number of oxide layers of the oxide layer 4 is 1, and the aperture of the oxide hole is 5 μm. It also comprises a first electrode 61 and a second electrode 62, the first electrode 61 is located on the substrate 1, and the second electrode 62 is located on the second DBR layer 5. The diameter of the Fresnel lens 51 is 8 μm, the number of turns is 20, and the width of each prism is 400 nm.
[0033] The parameters of the Fresnel lens are as follows, where f is the required focal length, the lens diameter D, R is the number of turns, n is the material refractive index, each prism width d, i means that there are a total of i prisms in the design, and A(i) is the angle between the center line of the i-th prism and the optical axis.
[0034] A(i)=90°-arctan(f / (d(i / 2-1 / 2)))
[0035] B(i)=arctan(sinA(i) / (n-cosA(i)))
[0036] The required etching angle can be calculated by the required focal length and the number of turns. Taking the traditional VCSEL epitaxial structure (GaAs) as an example, a photoresist or polymer sensitive to ultraviolet light is spin-coated on the surface of the second DBR layer 5.
[0037] The main speed of the coating is 2500-3000rpm, the coating time is 20-30s, the coating amount is 5-10mL, the thickness of the photoresist or polymer is 2-2.5um, and the mold template is used to fix the photoresist and then irradiate ultraviolet light. The development adopts a three-stage development, the first stage development time is 0.5-1s, the second stage development time is 25-30s, and the third stage development time is 25-30s, and finally a photoresist in the shape of a Fresnel lens is obtained. Dry etching is performed using a gas with a high etching selectivity ratio (BCL3:CL2:N2=5~10:5~10:40~60), the etching angle is 13.4°, and a ring-shaped pattern is etched at the light window position (GaAs), and finally a Fresnel lens 51 is formed, such as Figure 2 As shown, Figure 2 yes Figure 1 Enlarged view of point G in the middle.
[0038] Embodiment 2, a vertical cavity surface emitting laser, includes a first DBR layer 2, an active layer 3, an oxide layer 4 and a second DBR layer 5 stacked in sequence on a substrate 1, a Fresnel lens 51 is formed on a surface of the second DBR layer 5 away from the substrate 1, and the Fresnel lens 51 is located above the oxide hole of the oxide layer 4, and also includes a first electrode 61 and a second electrode 62, the first electrode 61 is located on the substrate 1, and the second electrode 62 is located on the second DBR layer 5.
[0039] The diameter of the Fresnel lens 51 is 9 μm, the number of turns is 50, and the width of each prism is 180 nm.
[0040] In this embodiment, the number of oxide layers 4 is 2, and the diameter of the oxide hole is 6 μm, but it can also be designed as a multi-layer oxide layer according to the performance requirements of the actual device. The multi-layer oxide layer is to further reduce the capacitance. For example, the number of oxide layers 4 is 3, 4 or 5.
[0041] Embodiment 3, a vertical cavity surface emitting laser, comprising a first DBR layer 2, an active layer 3, an oxide layer 4 and a second DBR layer 5 stacked in sequence on a substrate 1, a Fresnel lens 51 is formed on the surface of the second DBR layer 5 away from the substrate 1, the Fresnel lens 51 is located above the oxide hole of the oxide layer 4, the aperture of the oxide hole is 7μm, and also comprises a first electrode 61 and a second electrode 62, the first electrode 61 is located on the substrate 1, and the second electrode 62 is located on the second DBR layer 5. The diameter of the Fresnel lens 51 is 10μm, the number of turns is 40, and the width of each prism is 250nm.
[0042] The utility model is a Fresnel lens prepared by nanoimprinting directly on the epitaxial layer of VCSEL at its light window (that is, the Fresnel lens is prepared in a traditional process technology). Compared with an externally packaged convex lens or concave lens, this process can reduce the volume of the laser after packaging.
[0043] The above description is only a preferred embodiment of the utility model and does not limit the technical scope of the utility model. Therefore, any changes or modifications made according to the claims and description of the utility model should fall within the scope of the utility model patent.
Claims
1. A vertical cavity surface emitting laser, characterized in that: The invention comprises a first DBR layer, an active layer, an oxide layer and a second DBR layer which are sequentially stacked on a substrate. A Fresnel lens is formed on a surface of the second DBR layer away from the substrate. The Fresnel lens is located above the oxide holes in the oxide layer.
2. A vertical cavity surface emitting laser according to claim 1, characterized in that: The diameter of the Fresnel lens is larger than the aperture of the oxide hole.
3. A vertical cavity surface emitting laser according to claim 1 or 2, characterized in that: The center of the Fresnel lens is on the same straight line as the center of the oxidation hole.
4. A vertical cavity surface emitting laser according to claim 1, characterized in that: The diameter of the Fresnel lens is 8-10 μm.
5. The vertical cavity surface emitting laser according to claim 1, characterized in that: The pore size of the oxidation pores is 5-8 μm.
6. A vertical cavity surface emitting laser according to claim 1, characterized in that: The number of circles of the Fresnel lens is 20-50, and the width of each prism of the Fresnel lens is 150-500nm.
7. The vertical cavity surface emitting laser according to claim 1, characterized in that: The device also includes a first electrode and a second electrode. The first electrode is located on the substrate, and the second electrode is located on the second DBR layer.
8. The vertical cavity surface emitting laser according to claim 1, characterized in that: The material of the substrate is N-type gallium arsenide, the material of the first DBR layer is N-type aluminum gallium arsenide, the material of the active area is indium gallium arsenide or aluminum gallium arsenic, the material of the second DBR layer is P-type aluminum gallium arsenic, the material of the first electrode is gold-germanium alloy or palladium-gold, and the second electrode is titanium-platinum-gold.
9. The vertical cavity surface emitting laser according to claim 1, characterized in that: A Fresnel lens prepared by ultraviolet nanoimprinting is formed on the surface of the second DBR layer away from the substrate.