A preparation method of DBR reflector and laser

Abstract

The present invention discloses a method for fabricating a DBR reflector. This method can efficiently transfer a DBR grown on a metal film to produce a low-threshold laser. Specifically, when the DBR is grown in a high-temperature ring, thermal stress from the metal film causes it to self-detach. Using tape to secure the detached DBR allows for secondary transfer. This method overcomes the limitations of traditional transfer techniques by utilizing the high-temperature environment during DBR growth to achieve self-detachment, making the process simpler and more efficient. Lasers fabricated using the transferred DBR can achieve higher performance.

Description

Technical Field

[0001] The invention relates to a preparation method of a DBR reflector and a laser, and belongs to the technical field of super surface optics. Background Art

[0002] Distributed Bragg reflectors (DBRs) are an important component of optical devices. They consist of multiple alternating thin layers of high-refractive index and low-refractive index materials stacked together to form a periodic structure. DBRs are widely used in lasers, fiber-optic communications, optoelectronic devices, optical sensing, and other fields due to their high reflectivity, wavelength selectivity, and manufacturing flexibility. DBR reflectors use the Bragg scattering effect to achieve efficient reflection of light of specific wavelengths. When incident light strikes the DBR, light diffraction occurs based on the difference in refractive index between the different material layers. Under certain conditions, these diffraction effects cause certain wavelengths of light to be reflected, while other wavelengths of light are transmitted or absorbed.

[0003] A DBR laser is a laser based on a distributed Bragg reflector (DBR). Its most typical structure is a vertical cavity surface emitting laser (VCSEL), which is widely used in optical communications, sensing, lidar and other fields. The main feature of a DBR laser is that the reflector of its resonant cavity is composed of a DBR layer, which selectively reflects light of a specific wavelength to achieve narrow bandwidth laser output. When current is injected into the active layer, electrons and holes recombine to produce photons, which are reflected back and forth between the DBR reflectors. The active layer provides gain, amplifying the optical signal. When the wavelength of the light matches the Bragg condition of the DBR reflector, the reflectivity reaches its maximum, a stable resonance is formed in the cavity, and laser light is output from the top DBR.

[0004] Compared with the traditional substrate structure, the substrate-free distributed Bragg reflector (DBR) eliminates the influence of the substrate on optical performance, making the DBR achieve higher reflectivity and more precise optical characteristics in a wider wavelength range. DBR grown on a substrate will encounter greater difficulties during transfer, and the DBR layer will be directly damaged when the substrate is peeled off. For example, SiO grown directly on a silicon substrate 2 / When transferring SiN stacked DBRs, wet etching the silicon substrate will simultaneously react with the SiO2 and damage the DBR layer. Therefore, a simple transfer method that does not damage the DBR layer is needed. Summary of the Invention

[0005] The invention discloses a preparation method of a DBR reflector, which overcomes the problem of poor effect of damaging the DBR layer when transferring the DBR by wet etching the substrate, realizes the complete transfer of the DBR, and ensures its high reflection performance and structural integrity.

[0006] The technical solution adopted in the present invention is:

[0007] A method for preparing a DBR reflector, comprising the following steps:

[0008] (1) Evaporating a metal thin film layer on a substrate;

[0009] (2) Annealing the metal film layer in N2 atmosphere;

[0010] (3) Using PECVD equipment to grow a DBR structure on the metal film layer;

[0011] (4) The thermal stress of the metal film is used to make the grown DBR peel off on its own.

[0012] Preferably, step (4) specifically refers to taping the DBR before cooling. Generally, the tape can be applied after the DBR growth is completed. After the DBR is naturally cooled to room temperature, the DBR is transferred to the desired device. The metal film has a significantly different thermal expansion coefficient from the DBR growth material. During the high-temperature growth process, stress accumulation between the material layers will occur, resulting in self-delamination of the DBR and the metal film layer after cooling. Using tape to tap the DBR can maintain the integrity of the DBR.

[0013] Preferably, step (2) is specifically: treating the metal film by rapid annealing at 300-500° C. for 5 to 15 minutes in a nitrogen atmosphere.

[0014] Preferably, the metal film layer is made of gold, silver or nickel, and has a thickness of 10-100 nm.

[0015] Preferably, the DBR is formed by stacking a low refractive index layer and a high refractive index layer, wherein the low refractive index layer / high refractive index layer is selected from SiO2 / TiO2, SiO2 / Si3N4 or AlGaN / SiO2, the thickness of each layer is 10-50nm, and the number of layers is 4 to 100, wherein the number of layers refers to the sum of the number of low refractive index layers and the number of high refractive index layers.

[0016] Preferably, the growth temperature of the DBR is 150-350°C.

[0017] The DBR reflector is prepared by the above-mentioned preparation method of the DBR reflector.

[0018] The invention also discloses a laser, which is made of the DBR reflector.

[0019] The beneficial effects of the present invention are:

[0020] 1. By controlling the deposition parameters of the PECVD equipment and the annealing conditions of the metal film, the DBR is effectively separated from the metal substrate, simplifying the process and improving production efficiency.

[0021] 2. The method of the present invention avoids the damage to the DBR that may be caused when removing the substrate by wet etching through the thermal stress self-stripping mechanism, thereby ensuring the integrity and optical performance of the reflector layer.

[0022] 3. The fixing effect of the tape during the peeling process further enhances the stability of the DBR structure, ensuring its mechanical strength and optical consistency in subsequent transfer and application.

[0023] 4. The transferred substrate-free DBR can be made into higher performance optical devices and can be used to prepare low-threshold lasers.

[0024] 5. The method of the present invention has wide applicability and can be used not only for DBR preparation and transfer, but also for the manufacture of thin film devices on other complex substrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the method for transferring DBR grown on a metal substrate.

[0026] Figure 2 Schematic diagram of the structure after growing a metal film on a substrate.

[0027] Figure 3 Schematic diagram of the structure after DBR is grown on the metal film.

[0028] Figure 4 Schematic diagram of the DBR structure after self-stripping.

[0029] Figure 5 This is a schematic structural diagram of the low-threshold laser manufactured in Example 1.

[0030] Figure 6 Schematic diagram of the DBR laser structure prepared by the traditional patch method in comparative example 1.

[0031] Figure 7 This is a photograph of the transferred DBR prepared in Example 1.

[0032] Figure 8 This is a photograph of the transferred DBR prepared in Comparative Example 1.

[0033] Figure 9 This is a diagram of the threshold data of the low-threshold laser obtained in Example 1.

[0034] Figure 10 This is the spectrum of the low-threshold laser prepared in Example 1.

[0035] Figure 11 This is the threshold data diagram of the DBR laser prepared in Comparative Example 1.

[0036] Figure 12This is the spectrum diagram of the DBR laser prepared in Comparative Example 1.

[0037] Description of the marks in the figure:

[0038] 1: Silicon substrate

[0039] 2: Metal film

[0040] 3: DBR layer prepared by stacking low refractive index layer and high refractive index layer

[0041] 4: Tape

[0042] 5: Perovskite quantum dot film

[0043] 6: GaAs substrate. DETAILED DESCRIPTION

[0044] The present invention will be further described below with reference to the examples, but the description of the examples does not limit the scope of protection of the present invention in any way.

[0045] Unless otherwise defined, all technical terms and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention pertains, and the terms used herein in the specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. In addition, although demonstrations of parameters containing specific values ​​may be provided herein, it should be understood that the parameters do not need to be exactly equal to the corresponding values, but may be approximated to the corresponding values ​​within an acceptable error tolerance or design constraint. Directional terms mentioned in the embodiments, such as "up", "down", "front", "back", "left", "right", etc., are only directions with reference to the accompanying drawings. Therefore, the directional terms used are intended to illustrate rather than to limit the scope of protection of the present invention.

[0046] Unless otherwise specified, the materials and instruments used in the following examples can be obtained from conventional commercial channels.

[0047] Example 1 A method for preparing a low-threshold laser using a transferred DBR mirror:

[0048] (1) In this embodiment, a silicon wafer is selected as the substrate and the silicon wafer is cleaned. The cleaning process is as follows: the silicon wafer is placed in an acetone solution and ultrasonicated for 10 minutes, then placed in an ethanol solution and ultrasonicated for 10 minutes, then rinsed with deionized water and blown dry.

[0049] (2) Figure 2 As shown, a gold (Au) thin film with a thickness of 50 nm is evaporated on a silicon substrate using an electron beam evaporation device (EBE).

[0050] (3) The gold film was annealed in a rapid annealing furnace (RTP) to eliminate stress. The annealing conditions were as follows: in a N2 atmosphere, the temperature was raised from room temperature to 500°C in 30 seconds, maintained for 5 minutes, and then cooled to room temperature in 30 seconds.

[0051] (4) Figure 3 As shown, the DBR layers are grown using plasma-enhanced chemical vapor deposition (PECVD) equipment. In this example, the low refractive index layer (L layer) is SiO2 with a thickness of 25nm and a refractive index of 1.46; the high refractive index layer is Si3N4 with a thickness of 15nm and a refractive index of 2.05. The conditions for PECVD growth of SiO2 are as follows: a 5% SiH4 / N2 mixed gas and N2O gas are introduced into the reaction chamber with flow rates of 100 sccm and 400 sccm respectively, and SiO2 is deposited on the substrate surface at a pressure of 300 mTorr, a power of 10 W, and a temperature of 350°C for 70 s; the conditions for PECVD growth of Si3N4 are as follows: a 5% SiH4 / N2 mixed gas, NH3 gas, and N2 gas are introduced into the reaction chamber with flow rates of 25 sccm, 20 sccm, and 400 sccm respectively, and Si3N4 is deposited on the substrate surface at a pressure of 500 Torr, a power of 50 W, and a temperature of 350°C for 100 s.

[0052] (5) Repeat step (4) 26 times to complete the deposition of the DBR. The resulting DBR has a 54-layer stacked structure.

[0053] (6) Figure 4 As shown in the figure, the DBR grown at 350℃ in this example will peel off due to the thermal stress of the metal. Figure 1 As shown, the DBR is glued with tape for secondary transfer. Figure 7 and Figure 8 Take a picture of the DBR being transferred in the lab.

[0054] (7) Figure 5 As shown in the figure, a MAPbBr3 perovskite solution is spin-coated on a transferred DBR, and then another transferred DBR is covered on it to make a vertical cavity surface emitting laser (VCSEL), with the active area being perovskite quantum dots. Figure 9 and Figure 10 As shown, the threshold of the DBR laser fabricated is significantly reduced.

[0055] Comparative Example 1: A method for preparing a DBR laser using a patch method:

[0056] (1) In this comparative example, GaAs and silicon wafers were selected as substrates for two groups of DBRs, respectively. The substrates were cleaned by placing the substrates in an acetone solution and ultrasonicating for 10 minutes, then placing the substrates in an ethanol solution and ultrasonicating for 10 minutes, then rinsing with deionized water and drying.

[0057] (2) Figure 3 As shown, the DBR layers are grown using plasma-enhanced chemical vapor deposition (PECVD) equipment. In this example, the low refractive index layer (L layer) is SiO2 with a thickness of 25nm and a refractive index of 1.46; the high refractive index layer is Si3N4 with a thickness of 15nm and a refractive index of 2.05. The conditions for PECVD growth of SiO2 are as follows: a 5% SiH4 / N2 mixed gas and N2O gas are introduced into the reaction chamber with flow rates of 100 sccm and 400 sccm respectively, and SiO2 is deposited on the substrate surface at a pressure of 300 mTorr, a power of 10 W, and a temperature of 350°C for 70 s; the conditions for PECVD growth of Si3N4 are as follows: a 5% SiH4 / N2 mixed gas, NH3 gas, and N2 gas are introduced into the reaction chamber with flow rates of 25 sccm, 20 sccm, and 400 sccm respectively, and Si3N4 is deposited on the substrate surface at a pressure of 500 Torr, a power of 50 W, and a temperature of 350°C for 100 s.

[0058] (3) Repeat step (2) 26 times to complete the deposition of DBR.

[0059] (4) Figure 6 As shown, the two DBR structures are firmly bonded together using a hot pressing process to form the final laser cavity structure, with the active region being a GaAs substrate.

[0060] (5) After the spectrometer test, the results are as follows Figure 11 and Figure 12 As shown, compared with Example 1, the threshold of the low-threshold laser prepared using the transferred DBR mirror has a significant decrease.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a DBR reflector, characterized in that The steps include: (1) Evaporating a metal thin film layer on a substrate; (2) Annealing the metal film layer in N2 atmosphere; (3) Using PECVD equipment to grow a DBR structure on the metal film layer; (4) Using the thermal stress of the metal film to make the grown DBR peel off by itself; Step (2) specifically comprises: rapidly annealing the metal film at 300-500° C. for 5-15 minutes in a nitrogen atmosphere to eliminate the intrinsic stress of the growing metal film; The metal film layer is made of gold, silver or nickel with a thickness of 10-100 nm; The growth temperature of DBR is 150-350℃.

2. The method for preparing a DBR reflector according to claim 1, wherein: Step (4) specifically refers to sticking the DBR with tape before cooling, and transferring the DBR to the desired device after it is naturally cooled to room temperature.

3. The method for preparing a DBR reflector according to claim 1 or 2, wherein: The DBR is formed by stacking a low refractive index layer and a high refractive index layer, wherein the low refractive index layer / high refractive index layer is selected from SiO2 / TiO2, SiO2 / Si3N4 or AlGaN / SiO2, the thickness of each layer is 10-50nm, and the number of stacked layers is 4 to 100.

4. The method for preparing a DBR reflector according to claim 3, wherein: The number of stacked layers of the DBR is 20-100.

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