Symmetrical structure cavity perovskite water-resistant laser and preparation method thereof

Abstract

A symmetrically structured perovskite water-resistant laser comprises a laser gain medium and a symmetrically structured resonant cavity, wherein the laser gain medium is a perovskite thin film luminescent material. The resonant cavity is composed of quartz SiO2 glass and includes a first reflector and a second reflector, which are bonded and encapsulated with UV-curing adhesive. The gain medium has high gain characteristics, facilitating population inversion and promoting low-threshold stimulated emission. The resonant cavity utilizes a parallel, symmetrical Fabry-Perot cavity structure, forming a sandwich with the perovskite gain medium. This effectively limits carrier transmission within the gain medium and generates optical feedback, enabling room-temperature and underwater laser emission under optical pumping.

Description

Technical Field

[0001] The present invention provides a perovskite laser, and in particular relates to a perovskite water-resistant laser with a symmetrical structure cavity and a preparation method thereof. Background Art

[0002] Perovskites are a class of compounds with an ABX3 structure. The A-site is typically a monovalent cation, the B-site is typically a divalent metal cation, and the X-site is currently typically a halogen anion. In recent years, perovskite materials have shown broad application prospects in solar cells, photodetectors, LEDs, and lasers due to their exceptional properties, such as high absorption coefficients, low defect state density, and long carrier diffusion lengths.

[0003] Due to the excellent gain characteristics of perovskite materials, their application as gain media in the laser field has rapidly developed. Considering the size requirements of miniaturized lasers, when the physical volume of the gain medium is reduced to subwavelength scales, optical gain must overcome cavity losses to generate laser resonant modes. Currently, most perovskite lasers are external cavity-free structures, utilizing total internal reflection caused by the refractive index difference between the perovskite laser and the surrounding environment to confine the light field within the gain medium. These structures include nanowires, nanosheets, microspheres, and cubes. External auxiliary cavity structures, such as external DBR and DFB structures, can also achieve excellent laser quality.

[0004] Vertical-cavity surface-emitting lasers (VCSELs) are considered an ideal light source for photonic integrated circuits (PICs). Their single-mode operation and surface-emitting properties produce a circular and astigmatism-free beam that is easily coupled to optical fibers and other optical components.

[0005] Photonic integrated circuits based on VCSEL structures, realized through superstructures, are compact and highly efficient, playing a vital role in fields such as data communications, optical sensing, imaging, and optical interconnection. The current mainstream VCSEL is composed of two parallel DBR mirrors. Each DBR mirror is formed by alternating high and low refractive index layers, each with an optical thickness of only a quarter wavelength, and can achieve a reflectivity of 0.99 or even higher at the resonant wavelength. However, VCSEL lasers are difficult to reduce in size, especially at the subwavelength scale, making it difficult to meet the requirements for further miniaturization of optical components in on-chip photonic information processing systems.

[0006] Further optimizing the cavity structure, combining it with excellent perovskite gain media, and meeting the requirements of low threshold and high quality have become the development trend of perovskite lasers. At present, most perovskite vertical cavity surface emitting lasers mainly use the traditional DBR structure to form a sandwich structure of perovskite materials. For example, patents CN 111446619 A, CN 110504618 A and CN111711072A respectively realize quasi-two-dimensional perovskite single crystal vertical cavity surface emitting lasers, perovskite single crystal thin film vertical cavity surface emitting lasers and quantum dot thin film vertical cavity surface emitting lasers. The above-mentioned approach of using traditional DBR structure cannot achieve the further development of miniaturized perovskite lasers, which is not conducive to the application of perovskite vertical cavity surface emitting lasers in photonic integrated chips. Summary of the Invention

[0007] To solve the above problems, the present invention aims to provide a resonant cavity with a simple structure suitable for perovskite micro-nano lasers, and combine it with a perovskite gain medium to realize a perovskite laser with a simple structure, high performance and low threshold.

[0008] To achieve the above objectives, the technical solutions of the present invention are as follows:

[0009] On the one hand, the present invention provides a perovskite water-resistant laser with a symmetrical structure cavity, comprising a first reflector, a laser gain medium layer and a second reflector. The laser gain medium layer is a perovskite material, which easily achieves population inversion and stimulated emission light amplification; the first reflector and the second reflector are made of quartz glass (n~1.46), forming a refractive index difference with the perovskite material (n~2.3); the laser gain medium layer is synthesized on the first reflector, and the second reflector is vertically and flatly pressed on the laser gain medium layer, and forms a symmetrical Fabry-Perot cavity mirror structure with the first reflector.

[0010] Furthermore, the vertical resonant cavity includes a first reflector and a second reflector, and the two reflectors work together to provide efficient feedback for the gain medium to achieve stimulated emission amplification.

[0011] Furthermore, the reflector is made of a single layer of silica glass with a selected thickness of 300 μm and a refractive index of about 1.46, which is lower than the refractive index of the perovskite material, so as to provide feedback conditions for the perovskite gain medium and effectively limit the transmission of emitted light inside the gain medium.

[0012] Furthermore, the perovskite gain medium is not limited to a single perovskite material, but is applicable to three-dimensional perovskite materials, quasi-two-dimensional perovskite materials or perovskite quantum dot materials.

[0013] Furthermore, the thickness of the gain medium layer is 120nm, and the sub-wavelength thickness perovskite laser meets the size requirements of the photonic integrated chip.

[0014] Furthermore, the selected excitation source is an optical pump source. Any nanosecond laser or femtosecond laser that meets the conditions can pump the gain medium to achieve population inversion and stimulated emission of light.

[0015] On the other hand, the present invention also provides a method for preparing a perovskite water-resistant laser with a symmetrical structure cavity, which is characterized in that the method comprises the following steps:

[0016] ① Apply the perovskite laser gain medium to the first reflector by thermal evaporation or spin coating, and the first reflector is made of quartz glass;

[0017] ② Vertically and flatly pressing a second reflector onto the perovskite laser gain medium to form a vertical cavity with a sandwich structure with the first reflector, wherein the second reflector is made of quartz glass;

[0018] ③Use UV glue to encapsulate the edge of the cavity mirror.

[0019] The laser gain medium is a perovskite material, prepared by thermal evaporation and spin coating. It features a large absorption coefficient, high luminescence quantum efficiency, and superior gain performance, making it easy to achieve population inversion. An optical pumping source is an optional excitation source. A nanosecond laser or femtosecond laser that meets these requirements can pump the gain medium, achieving population inversion and stimulated emission of light.

[0020] The first reflector serves as a substrate, and the perovskite gain medium layer is synthesized by a related method, including but not limited to thermal evaporation, solution method, and chemical deposition method, and is grown on the first reflector. The second reflector is vertically and flatly pressed on the perovskite gain medium, forming a symmetrical Fabry-Perot cavity mirror structure with the first reflector.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1) The use of SiO2 cavity mirrors and UV adhesive packaging can protect the perovskite from environmental influences, isolate it from air and moisture, and increase the stability of the perovskite; at the same time, it does not affect the optical properties of the perovskite film and can operate underwater.

[0023] 2) The gain medium has high gain characteristics, which facilitates the realization of population inversion and is conducive to the generation of low-threshold stimulated emission. The resonant cavity adopts a parallel symmetrical Fabry-Perot cavity structure, forming a sandwich with the perovskite gain medium. This can effectively limit the carrier transmission in the gain medium and form optical feedback. Under optical pumping, it can achieve room temperature and underwater laser emission.

[0024] 3) Compared with the solution method, the perovskite gain medium prepared by thermal evaporation: 1. It is easy to precisely control the film thickness and has high repeatability (the thermal evaporation equipment can control the evaporation rate and crystallization rate); 2. The high vacuum preparation environment makes the film prepared by thermal evaporation have fewer defects; 3. The film quality is high and uniform (the solution method has uneven element distribution and uneven film surface); 4. No precursor is required during the preparation process, and the preparation process is non-toxic. The above advantages make the perovskite gain medium prepared by thermal evaporation able to achieve large-scale production line manufacturing

[0025] 4) UV glue is widely used in the chip industry to effectively bond and package the first reflector, the gain medium layer, and the second reflector, and plays a great role in isolating water and air from the external environment, further improving the stability of the perovskite gain medium and realizing underwater laser emission.

[0026] 5) Using a single-layer SiO2 laser resonator, combined with a high-gain perovskite material (excellent stimulated emission properties), the large refractive index difference facilitates efficient optical feedback, thus generating lasing. This invention eliminates the need for multi-layer structures and larger DBRs, and the single-layer SiO2 resonator is more suitable for photonic chip integration.

[0027] 6) The preparation method is simple, the price is low, the sub-wavelength size can achieve excellent beam output, which is convenient for meeting the needs of on-chip integration and has a wide range of applications in on-chip optical communications, sensing, optical computing and optical image processing.

[0028] 7) A perovskite laser with excellent water resistance was achieved, which provides ideas for overcoming the extremely poor stability of perovskite materials and moving devices towards commercial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Schematic diagram of the structure of a perovskite water-resistant laser with a symmetrical cavity structure;

[0030] Figure 2 The fluorescence spectrum of the perovskite water-resistant laser with a symmetrical cavity structure;

[0031] Figure 3 The laser spectrum of the perovskite water-resistant laser with a symmetrical cavity structure varies with power under femtosecond laser excitation;

[0032] Figure 4 This is a picture of the intensity change of a perovskite water-resistant laser with a symmetrical structure cavity as the power changes.

[0033] Figure 5 Laser linewidth spectrum of perovskite water-resistant laser with symmetrical cavity structure.

[0034] Figure 6 Laser polarization degree of perovskite water-resistant laser with symmetrical cavity structure. DETAILED DESCRIPTION

[0035] The technical solutions of the present invention will be further explained in detail below with reference to the accompanying drawings in the embodiments of the present invention, but this should not limit the scope of protection of the present invention.

[0036] See also Figure 1 , Figure 1 This is a schematic diagram of the structure of a symmetrical cavity perovskite water-resistant laser. As shown in the figure, the structure of a symmetrical cavity perovskite water-resistant laser, from bottom to top, is the first reflector, the perovskite gain medium layer, and the second reflector. In this example, the first and second reflectors are both made of quartz SiO2 glass. For experimental feasibility, a thickness of 300μm was selected, but this thickness is not limited.

[0037] First, a perovskite film is prepared. To achieve high-quality, high-gain, and uniform perovskite film, thermal evaporation is used to uniformly deposit the perovskite onto the first reflector. In this example, a three-dimensional all-inorganic perovskite (CsPbBr3) was used for experiments. Efficient and precise control of the experimental sample preparation enabled a subwavelength film thickness of 120nm, paving the way for on-chip light source technology.

[0038] The second reflector is then vertically and flatly pressed onto the perovskite gain medium to form a symmetrical Fabry-Perot structure optical resonant cavity, which can effectively achieve photon confinement and further form optical feedback to produce stimulated emission light amplification.

[0039] In addition, the upper and lower parts and edge parts of the two reflectors are sealed with UV glue.

[0040] The optical resonant cavity formed by the two SiO2 reflectors can achieve considerable resonance performance by combining the above schemes. For the perovskite gain medium, this embodiment uses CsPbBr3 perovskite as an example, and its material gain is as high as 10 4 cm -1 After optical pumping, light amplification is achieved inside the gain medium, the resonant cavity can effectively achieve light confinement, and further form resonant feedback to generate laser.

[0041] Figure 2The fluorescence spectrum of a perovskite water-resistant laser with a symmetrical cavity structure is shown. A 405nm continuous light semiconductor laser was used to excite the device shown in the experiment. The pump density was relatively low, insufficient to achieve stimulated emission. As can be seen from the fluorescence spectrum, the fluorescence spectrum with a Gaussian profile at a central wavelength of 519nm is not a smooth fluorescence spectrum, but rather has many small peaks distributed throughout the Gaussian profile. This is due to the strong confinement effect of the first and second reflectors, which form an efficient resonant cavity and exert a strong confinement effect on the emitted photons. This interference phenomenon, indicating the presence of a Fabry-Perot cavity effect, demonstrates that the simple structure of the first and second reflectors meets the basic requirements of a resonant cavity, can provide optical feedback for the perovskite gain medium, and further achieve stimulated emission light amplification.

[0042] The UV adhesive packaging of the reflector edge is widely used in the chip industry. It can be used here to effectively bond the first reflector and the second reflector, and plays a great role in isolating water and air from the external environment, further improving the stability of the perovskite gain medium.

[0043] The stimulated emission experiment used a frequency-doubled femtosecond laser source (400nm, 1kHz, 35fs). The figure shows the emission spectra of four different pump power densities, from low to high: 14.24μJ / cm 2 ,23.74μJ / cm 2 ,33.24μJ / cm 2 ,42.73μJ / cm 2 As can be seen from the figure, under low pump density excitation (14.24μJ / cm 2 ), there is only one curve with very low intensity, according to Figure 2 Judging from the position of the fluorescence peak, this very low intensity peak is centered at 519nm. Continue to increase the pump density to more than 17μJ / cm 2 A sharp emission peak appears near 535nm, with a peak width of less than 1nm, which is consistent with the narrow linewidth characteristics of the laser peak. 2 In addition to the main laser peak at 535 nm, there are two small peaks with very weak intensity at 42.73 μJ / cm 2 It is most obvious when , which is manifested as the obvious evolution characteristics of Fabry-Perot mode laser. Figure 4The curve depicts the change in emission intensity as power changes. Observation revealed that the emission intensity changes from a linear relationship with a low slope to a linear relationship with a high slope as power changes, indicating a sharp increase in intensity due to laser emission, further confirming the laser emission phenomenon. The inflection point of the slope can also be extracted, i.e., the threshold value is 17 μJ / cm 2 . Figure 5 The fitting results show that the laser linewidth is 0.319 nm, corresponding to a quality factor of 1677. Figure 6 It shows that the linear polarization degree of the emitted laser is 67%.

[0044] The above experimental phenomena verify a water-resistant perovskite laser with a simple structure. The perovskite material involved has excellent gain properties, with high absorption coefficient and gain coefficient, which easily achieves population inversion and facilitates the further realization of stimulated emission light amplification. The simple cavity mirror structure involved is sufficient to meet the resonant cavity requirements for the perovskite gain medium, forming an effective refractive index difference with the gain medium, thereby achieving light confinement and further providing optical feedback to achieve lasing. Its water-resistant properties ensure the stable operation of the laser in air. Its simple resonant cavity structure is more convenient for meeting the requirements of on-chip integration and has a wide range of applications in on-chip optical communications, sensing, optical computing, and optical image processing.

Claims

1. A perovskite water-resistant laser with a symmetrical cavity structure, comprising a first reflector, a laser gain medium layer, and a second reflector, characterized in that: The laser gain medium layer is made of perovskite material, which can easily achieve population inversion and stimulated emission light amplification; the first reflector and the second reflector are made of quartz glass, forming a refractive index difference with the perovskite material; the laser gain medium layer is synthesized on the first reflector, and the second reflector is vertically and flatly pressed on the laser gain medium layer, and forms a symmetrical Fabry-Perot cavity mirror structure with the first reflector.

2. The perovskite water-resistant laser with a symmetrical structure cavity according to claim 1, characterized in that: The perovskite material is a single type of perovskite material, or a three-dimensional perovskite material, a quasi-two-dimensional perovskite material or a perovskite quantum dot material.

3. The perovskite water-resistant laser with a symmetrical cavity structure according to claim 1, characterized in that: The thickness of the laser gain medium layer is sub-wavelength scale, and the thickness is 40-500 nm.

4. The perovskite water-resistant laser with a symmetrical cavity structure according to claim 1, characterized in that: The first reflector and the second reflector are bonded and packaged with ultraviolet curing adhesive.

5. The perovskite water-resistant laser with a symmetrical structure cavity according to any one of claims 1 to 4, characterized in that: The first reflector and the second reflector are made of single-layer silica glass with a thickness of 300 μm and a refractive index of 1.46, which is lower than the refractive index of the perovskite material, providing feedback conditions for the perovskite gain medium and effectively limiting the transmission of emitted light inside the gain medium.

6. A method for preparing a perovskite water-resistant laser with a symmetrical structure cavity, characterized in that: The steps include: ① Apply the perovskite laser gain medium to the first reflector by thermal evaporation or spin coating, and the first reflector is made of quartz glass; ② Vertically and flatly press the second reflector onto the perovskite laser gain medium to form a vertical cavity with a sandwich structure with the first reflector. The second reflector is made of quartz glass. ③ Use UV glue to encapsulate the edge of the cavity mirror.

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