Method for preparing perovskite nano laser array by utilizing scatterer coupled evanescent wave emission

Abstract

The invention discloses a method for preparing a perovskite nano laser array by utilizing scatterer coupling evanescent wave emission, and relates to the technical field of optical devices. The method provided by the invention comprises the following steps: (1) preparing an MAPbBr3 perovskite microdisk; (2) preparing a scatterer array structure; (3) transferring the MAPbBr3 perovskite micro-disk to the scatterer array structure, and completing sample assembly; and (4) a scatterer array structure is designed, femtosecond light with the wavelength of 400 nm is used for pumping, and the perovskite nano laser array is prepared. The contradiction between the quality factor and the integration level of a single resonant cavity of a traditional laser array is solved, on the whole cavity, through the scattering effect of coupling output with evanescent waves on the surface of the cavity, the periodically-arranged scatterers output laser with basically consistent radiation, and the quality factor and the integration level of the single resonant cavity are improved. Therefore, the perovskite nano laser array has higher integration level and more uniform radiation.

Description

Technical Field

[0001] The invention relates to the technical field of optical devices, and in particular to a method for preparing a perovskite nano laser array by utilizing scatterer-coupled evanescent wave emission. Background Art

[0002] Since the appearance of the world's first ruby ​​laser, the research on laser science and technology has expanded rapidly and has been applied in various fields such as industry, weapons, medical treatment, and scientific research. Among them, compact and miniaturized micro-nano lasers have always been a research hotspot in the scientific research and industrial circles. After decades of development, various micro-nano lasers such as vertical cavity surface emitting lasers (VCSELs), micro-disk lasers, photonic crystal lasers, and nanowire lasers have appeared one after another. The theory of laser generation is stimulated radiation, which refers to the phenomenon that atoms in the excited state energy level transition to a lower energy level and radiate the same photons under the action of external photons. Therefore, the selection of suitable gain materials is very important for the research of micro-nano lasers. Traditional optoelectronic functional materials have many limitations in the application of lasers, such as low carrier mobility and poor laser performance of organic materials, and poor flexibility and difficulty in integration of inorganic semiconductor materials. The new organic and inorganic hybrid perovskite system is expected to break through the above bottlenecks in laser applications. As the gain medium of laser, perovskite has the advantages of being able to be prepared from low-temperature solutions, high optical absorption coefficient, low defect state density, high carrier mobility, high optical net gain, and high refractive index, which are helpful in designing compact light-emitting devices.

[0003] Various studies at home and abroad have given many research plans for constructing micro-nano laser arrays using perovskites. One method is to control the growth area of ​​perovskite with the help of a mask, such as using a periodically arranged silicon template or a cylindrical hole template to limit the distribution range of the perovskite precursor solution, and nucleate and grow a large-area array with a minimum unit size of 2.1um in a fixed area. Another method is to use a top-down etching method to pattern the perovskite, such as using a donut-shaped femtosecond laser beam to directly ablate the perovskite film on the glass to form a microdisk laser array. The array can reach the chip level and the size uniformity between units is good, or focused ion etching technology is used to prepare concentric ring grating lasers on ultra-thin perovskite single crystal films, etc. Other methods include placing perovskite crystals on gold films to achieve submicron-sized plasma lasers, or combining perovskite microdisks with metasurfaces, etc.

[0004] The two key indicators for evaluating nanolaser arrays are integration density and uniformity of laser unit radiation. The method of confined growth of perovskite with the help of a mask requires the separation of the precursor solution, resulting in a large period of the laser array, which is difficult to further compact. And because the crystal growth process follows the law of self-assembly, the crystal size is at least in the micron level, and the quality has obvious differences, making it difficult to ensure the uniformity of unit radiation. Another method of patterning perovskite materials is affected by the scattering of sputtered particles during laser ablation and the unevenness of the sample edge. The threshold and line width of the laser are usually poorly uniform, and its mode volume is much larger than the physical size, resulting in the period of the laser array composed of this structure being much larger than the size of the laser unit, limiting the integration density. The focused ion beam etching method has high requirements on the size and thickness of the perovskite single crystal, and the space occupied by a single annular grating is large, which is not conducive to high integration.

[0005] In addition, although the surface plasmon mode of the perovskite plasma laser can compress the laser mode into the dielectric layer between the perovskite and the gold substrate in the thickness direction, the mode in the other two dimensions still extends outside the resonant cavity. In addition, the coupling compatibility between the plasmon mode and the on-chip photonic circuit is poor, which is not conducive to integration. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a perovskite nano-laser array by using scatterers to couple evanescent waves. The present invention solves the contradiction between the quality factor and integration of a single resonant cavity of a traditional laser array. In a whole cavity, by utilizing the scattering effect of the evanescent wave coupled output with the cavity surface, the periodically arranged scatterers output lasers with basically uniform radiation, thereby making the perovskite nano-laser array have a higher integration and more uniform radiation.

[0007] To achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for preparing a perovskite nano-laser array by utilizing scatterer-coupled evanescent wave emission, comprising the following steps:

[0009] (1) Preparation of MAPbBr3 perovskite microdisks;

[0010] (2) Pre-treating the substrate; then spin-coating PMMA on the substrate, drawing a pattern using electron beam lithography, developing the pattern by immersion in methyl isobutyl ketone / isopropyl alcohol (MIBK / IPA, volume ratio of 1:3), and fixing the pattern by immersion in isopropyl alcohol; after chrome plating, immersing the substrate in a degumming solution and heating it at 75-80°C for 10-12h, cleaning it with an acetone gun for stripping, cleaning it with isopropyl alcohol, and etching it after drying it, and then immersing it in an acid solution for chrome removal, and obtaining a scatterer array structure after cleaning and drying it;

[0011] (3) Transferring the MAPbBr3 perovskite microdisk to the scatterer array structure to complete the sample assembly;

[0012] (4) Design the scatterer array structure and then use femtosecond light pumping with a wavelength of 400nm to prepare a large-area uniform perovskite nanolaser array.

[0013] The present invention utilizes the scattering effect of the evanescent wave coupled output from the cavity surface to allow the periodically arranged scatterers to output lasers with basically uniform radiation. The present invention selects silicon materials, and the higher refractive index not only has better scattering effects, but also has stronger localization capabilities, which enables smaller array sizes and periods. In addition, silicon on-chip integration technology is more mature, and the sizes and shapes of the prepared units are highly uniform. Therefore, the method of the present invention can rapidly increase the integration density while ensuring the radiation uniformity between array units to the greatest extent.

[0014] The principle of the present invention is that the perovskite microdisk cavity is used as the cavity for laser generation, and it can emit laser light by optical pumping. When the perovskite microdisk cavity generates laser light, there is an evanescent wave on its surface along the direction of light oscillation. Since the refractive index of the silicon scatterer material is higher than that of the perovskite microdisk cavity material, the evanescent wave is easily coupled into the silicon scatterer particles, changing the laser direction of the perovskite microdisk cavity and scattering it from the vertical plane. Therefore, by designing the period and size of the silicon scatterer array, high density can be achieved. In addition, the laser light scattered from the same perovskite microdisk resonant cavity can achieve uniform radiation.

[0015] Preferably, the method for preparing the MAPbBr3 perovskite microdisk in step (1) comprises the following steps:

[0016] MABr and PbBr2 with a molar ratio of 1:1 were dissolved in N,N-dimethylformamide (DMF) and stirred for 3-4h to obtain a perovskite precursor solution;

[0017] The perovskite precursor solution was then dropped onto ITO and transferred to a gauze soaked in dichloromethane at the bottom, sealed, and placed at room temperature for 48 h to obtain a MAPbBr3 perovskite microdisk.

[0018] Preferably, the MA is methylammonium, and its chemical formula is [CH3NH 3+ ].

[0019] Preferably, the degumming liquid in step (2) is Remover PG. Remover PG is a proprietary high-efficiency solvent remover based on NMP (N-methylpyrrolidone, chemical formula C5H9NO), which can remove PMMA and other resist film substrate surfaces and can also be used as a stripping solvent.

[0020] Preferably, in the step (2), the substrate (SOI) comprises, from bottom to top, a silicon substrate, a silicon dioxide layer with a thickness of 3 μm, and a silicon layer with a thickness of 220 nm.

[0021] Preferably, in step (2), the substrate is pretreated by the following steps:

[0022] The substrate was soaked in acetone, isopropanol, and deionized water for 8-10 min each, and then dried in nitrogen.

[0023] Preferably, the scatterer array structure in step (2) comprises a silicon layer and a perovskite microdisk cavity.

[0024] The scatterer nanocube array structure located on the substrate is used to couple the evanescent wave emission from the surface of the perovskite resonant cavity.

[0025] Preferably, the perovskite micro-disk cavity has a width of 15-80 um, a length of 30-100 um, and a thickness of 200-600 nm; and the material of the perovskite is methylamine lead bromide.

[0026] In the present invention, the thickness is selected in the range of 200nm to 600nm, and the thinner the thickness, the better the effect. If the thickness is less than 100nm, FP laser cannot be generated; if the thickness is greater than 600nm, the scatterer coupling emission effect is poor and the laser threshold is high. Therefore, the present invention controls the size of the perovskite microdisk cavity within the above range, so that the perovskite nanolaser array has a higher integration and more uniform radiation.

[0027] Preferably, in step (2), the scatterer unit cells of the silicon layer are arranged periodically, and the period of the scatterer structure is between 400-1000 nm.

[0028] Preferably, in the step (2), the shape of the nanostructures in the unit cells of the silicon layer is a cuboid or a cube, with a length and a width of 160-200 nm.

[0029] Preferably, the thickness of the nanostructure within the unit cell of the silicon layer in step (2) is 100-300 nm, preferably 220 nm.

[0030] Preferably, in step (4), the energy of the amplifying stage light outlet of the femtosecond optical pump is 4 mJ, the repetition frequency is 1 kHz, and the pulse width is 100 fs.

[0031] The emission mentioned in the present invention refers to emitting the laser light leaked only on both sides of the perovskite microdisk from a vertical direction.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention realizes a uniformly emitting laser array with a minimum period of 400nm and a unit cell of 200nm through an optimized design of the combination of a scatterer array and a perovskite microdisk cavity, and the laser threshold is only increased by 2 times. At the same time, the vertical surface emission capability of the perovskite microdisk cavity is improved, and the laser utilization rate is increased.

[0034] (2) Since the scatterer array couples the evanescent wave on the surface of the perovskite FP cavity (Fabry–Pérot cavity) to perform laser coupling emission, the method described in the present invention is also applicable to FP cavities of other materials, and a compact multi-channel coherent light source can be realized.

[0035] (3) The preparation method of the present invention is relatively simple, the sample transfer is simple, and only one layer of structure etching is required. At the same time, the micro-nano preparation process of silicon is mature, which realizes the preparation of laser arrays with low cost and high processing speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the perovskite nanolaser array of the present invention.

[0037] Figure 2 It is a schematic diagram of the preparation performance of the perovskite nanolaser device described in the present invention.

[0038] Figure 3 It is a schematic diagram of the ability of the scatterer unit cell to couple laser energy according to the present invention.

[0039] Figure 4 It is a schematic diagram of the performance of the high-resolution laser device described in the present invention.

[0040] Figure 5 Schematic diagram of 9 different perovskite microdisk thresholds with and without scatterer array structures described in the present invention. DETAILED DESCRIPTION

[0041] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments, but the protection scope and implementation methods of the present invention are not limited thereto.

[0042] Unless otherwise specified, the materials and reagents used in the following examples are commercially available.

[0043] Example 1

[0044] A method for preparing a high perovskite nanolaser array by using scatterer-coupled evanescent wave emission, comprising the following steps:

[0045] (1) Preparation of MAPbBr3 perovskite microdisks:

[0046] The perovskite single crystal MAPbBr3 was grown by a one-step solution method. MABr (purity 99.99%) and PbBr2 (purity 99.99%) with a molar ratio of 1:1 were dissolved in N,N-dimethylformamide (DMF) and stirred for 4 hours to obtain a 1 mol / L perovskite precursor solution; MA is methylammonium;

[0047] Then, 10uL of 0.02mol / L perovskite precursor solution was dropped on a 1.5cm×1.5cm 135nm thick ITO, and then transferred to a beaker with 8mL of gauze soaked in dichloromethane at the bottom. Finally, the beaker was sealed with two layers of 3DParafilms. After being placed at room temperature and in a ventilated place for 48 hours, the synthesis of the MAPbBr3 perovskite microdisk was completed.

[0048] (2) Preparation of scatterer array structure:

[0049] The electron beam resist pattern is produced using electron beam lithography.

[0050] The SOI substrate was immersed in acetone, isopropanol, and deionized water in the order of 10 min each, and then dried with a nitrogen gun. Figure 1 As shown, the substrate includes a silicon substrate, a silicon dioxide layer with a thickness of 3 μm, and a silicon layer with a thickness of 220 nm from bottom to top.

[0051] Spin-coat polymethyl methacrylate (PMMA A2) on the substrate, draw the pattern using electron beam lithography, soak in MIBK / IPA (volume ratio of 1:3) for 30 seconds for development, and then soak in isopropanol for 10 seconds for fixing. After coating 20nm thick chromium with a coating machine, soak the substrate in Remover PG and heat it at 80℃ for 12h, clean it with an acetone gun for stripping, then clean it with isopropanol, and finally blow it dry with a nitrogen gun. Etch it with an inductively coupled plasma etching device (ICP), soak it in concentrated nitric acid for 2 minutes to remove the chromium, rinse it with clean water and blow it dry, and finally obtain a scatterer silicon array structure. Finally, use an optical fiber fixed on a three-dimensional translation stage to transfer the MAPbBr3 perovskite microdisk from ITO to the scatterer silicon array to complete the sample assembly.

[0052] Figure 2This is a SEM of the prepared perovskite nanolaser array. It can be seen that the SEM edge of the laser array prepared by the present invention is smooth, the side wall is vertical, and the perovskite resonant cavity is close to the array.

[0053] Figure 2 A is the overall image of the structure on SOI. The middle part is hollowed out with a size of 20×20um, but in the middle there is a scatterer unit cell of the same size as the surrounding 200nm unit cells with a period of 800nm.

[0054] Figure 2 B is a top view of an array structure with a size of 200 nm and a period of 800 nm.

[0055] Figure 2 C is a 45° oblique view of a 200nm array structure with a 800nm ​​period.

[0056] Figure 2 D is the overall image after structural transfer of the perovskite microdisk on the first SOI.

[0057] (3) Structural design of perovskite nanolaser array:

[0058] The overall size is 50×50um, the size of the scatterer unit cell is 200×200nm, the outer circle period is 800nm, the middle is a single unit cell particle, and the outer circle of 800nm ​​small period array can provide support for the perovskite resonant cavity microdisk, which is conducive to transfer. A small hole is added in the experimental optical path (in front of the collection end) so that the collection end can only collect the spectral information of the middle scatterer unit cell, such as Figure 3 As shown in A. Figure 3 B shows that under the 1800-line grating, the overall laser and the laser mode of the scatterer unit cell are consistent. Figure 3 C is the laser threshold information of the scatterer unit cell, which verifies the ability of the scatterer unit cell to emit the laser generated by the perovskite microdisk cavity by coupling the evanescent wave on the surface of the perovskite microdisk cavity. The second structure changes the middle unit cell into a 5×5 array with a period of 5um. The array with a large period of 5um in the middle is convenient for collecting single particle information through a small hole for comparison in the experiment. The spectral information of a single scattering unit collected is shown in Figure 3 As shown in D, the number and position of laser peaks of the four scatterer units are basically the same, indicating that each scatterer unit cell couples and emits the laser generated by the same perovskite microdisk cavity.

[0059] (4) Preparation of large-area uniform laser arrays:

[0060] The entire structure is a scatterer array structure with a uniform period. By changing the unit size and period, a series of laser arrays of different sizes are obtained. Figure 4As shown in A and B, the top is a microdisk cavity with a thickness of 568nm and a size of 29.3um×71.4um, and the bottom is an array with a period of 800nm ​​and a duty cycle of 1 / 4. The sample was pumped with femtosecond light of a wavelength of 400nm, the energy of the light output port of the amplifier stage was 4mJ, the repetition frequency was 1kHz, and the pulse width was 100fs. The bottom unstructured perovskite microdisk cavity only emits light on both sides, while the middle part is dark. The bottom structured perovskite microdisk cavity emits light on both sides, and the array below the middle is clearly visible, confirming that the scatterer array structure can couple with the evanescent wave on the microcavity surface to achieve laser emission. Figure 4 C Display Figure 4 The light-emitting point in B has 25 peaks at 20um in the x direction, which is consistent with the designed 800nm ​​periodic array. And each light-emitting unit has uniform brightness and clear boundaries. Under the experimental conditions, the minimum lateral size and period of the laser unit are 50nm and 400nm, respectively. Figure 4 As shown in D, the thickness of the perovskite microdisk cavity is 176nm. Figure 4 E and Figure 4 F shows that there are 5 luminescence peaks in a length of 2um, which is consistent with the periodic design. Finally, a unit cell of 160nm×160nm and a packing density of 6.25 million / mm were achieved. 2 The laser array has broken through the existing perovskite laser array integration density (the current minimum period is 2-3um).

[0061] like Figure 5 , perovskite microdisks with a thickness ranging from 300nm to 600nm were transferred to 9 structures with the same period of 800nm ​​and a scatterer unit cell size of 200nm. Each perovskite has a part suspended in the air and the other part on the structure. By comparison, it was found that the laser threshold of the perovskite on the structure is almost only about twice that of the suspended part. This technical method can simultaneously obtain micro-nano laser arrays with high integration density, high wavelength uniformity and narrow linewidth, providing a way to achieve high-throughput sensing and high-density coherent light sources, and is of great significance to the miniaturization and integration of micro-nano lasers.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission, characterized in that: The following steps are involved: (1) Preparation of MAPbBr3 perovskite microdisks; (2) Pre-treating the substrate; then spin-coating PMMA on the substrate, drawing a pattern using electron beam lithography, developing the pattern by immersion in methyl isobutyl ketone / isopropanol, and fixing the pattern by immersion in isopropanol; after chrome plating, immersing the substrate in a degumming solution and heating it at 75-80° C. for 10-12 hours, cleaning it with an acetone gun for stripping, cleaning it with isopropanol, and etching it after drying it, and then immersing it in an acid solution for chrome removal, and obtaining a scatterer array structure after cleaning and drying it; (3) Transferring the MAPbBr3 perovskite microdisk to the scatterer array structure to complete the sample assembly; (4) Designing the scatterer array structure and then using femtosecond light pumping with a wavelength of 400 nm to prepare a perovskite nanolaser array.

2. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 1, characterized in that: The method for preparing MAPbBr3 perovskite in step (1) comprises the following steps: MABr and PbBr2 with a molar ratio of 1:1 were dissolved in N,N-dimethylformamide and stirred for 3-4h to obtain a perovskite precursor solution; The perovskite precursor solution was then dropped onto ITO and transferred to a gauze soaked in dichloromethane at the bottom, sealed, and placed at room temperature for 48 h to obtain a MAPbBr3 perovskite microdisk.

3. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 1, characterized in that: In the step (2), the substrate is pretreated, and the steps are as follows: The substrate was soaked in acetone, isopropanol, and deionized water for 8-10 min each, and then dried in nitrogen.

4. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 1, characterized in that: The scatterer array structure in step (2) includes a silicon layer and a perovskite microdisk cavity.

5. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 4, characterized in that: The perovskite microdisk cavity has a width of 15-80 um, a length of 30-100 um, and a thickness of 200-600 nm.

6. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 4, characterized in that: In the step (2), the scatterer unit cells of the silicon layer are arranged periodically, and the period of the scatterer structure is between 400-1000nm.

7. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 4, characterized in that: In the step (2), the shape of the nanostructure in the unit cell of the silicon layer is a cuboid or a cube, and the length and width are both 160-200 nm.

8. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 4, characterized in that: In the step (2), the thickness of the nanostructure within the crystal cell of the silicon layer is 100-300 nm.

9. The method for preparing a perovskite nanolaser array by using scatterer-coupled evanescent wave emission as claimed in claim 1, characterized in that: In the step (4), the energy of the amplifying stage light outlet of the femtosecond optical pump is 4 mJ, the repetition frequency is 1 kHz, and the pulse width is 100 fs.

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