Organic single crystal microdisk array and echo wall mode microcavity laser based on same

Abstract

The invention discloses an organic single-crystal micro-disk array and an echo wall mode microcavity laser based on the same, relates to the field of organic single-crystal micro-disk arrays, and aims to solve the problems of random crystal orientation, non-uniform size and short crystal life in the prior art. The adopted technical scheme is as follows: a construction method of the organic single-crystal micro-disk array comprises the following steps: preparing a porous array template; and covering the template on the substrate with the organic semiconductor material precursor solution, enabling the precursor solution to enter the porous space, finally volatilizing the solvent in the organic semiconductor material precursor solution, and removing the PDMS template. According to the invention, accurate positioning and controllable morphology of the crystal structure are realized, the solvent volatilization of the organic semiconductor material precursor solution is more efficient, and the time cost is reduced; and crystal growth and micro-disk array forming do not need heating and pressurizing, and the requirements for the preparation environment and preparation equipment are low. The method has good compatibility with preparation processes of lasers and other traditional devices.

Description

Technical Field

[0001] The present invention relates to the technical field of organic single crystal microdisk arrays, and specifically to an organic single crystal microdisk array and a whispering gallery mode microcavity laser based on the microdisk array. Background Art

[0002] The solution method is a simple method for preparing whispering gallery mode organic lasers. However, the solution evaporation process is usually dominated by isotropic surface evaporation kinetics, resulting in randomly oriented crystals and non-uniform grain sizes. This brings difficulties to the controllable preparation of crystal structures and the integration of organic solid-state micro lasers.

[0003] Chinese Patent CN113073391A discloses a method for preparing an organic semiconductor single crystal array. The technical solution adopted is to construct a patterned nucleation template on the substrate surface, and then place the substrate coated with organic semiconductor particles above the nucleation template, making the pattern opposite to the organic semiconductor particles and spaced at a certain distance. By heating the substrate, it is melted on the nucleation template and recrystallized to prepare an organic semiconductor single crystal array. The prepared organic crystals are severely damaged due to the high-temperature melting preparation method, affecting the luminescence lifetime of the organic crystals. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the existing defects and provide an organic single crystal microdisk array and a whispering gallery mode microcavity laser based on the microdisk array, which can effectively solve the problems in the background art.

[0005] In order to achieve the above object, the present invention first discloses an organic single crystal microdisk array. The technical solution adopted is that its construction method includes the following steps: Step 1, prepare a porous array template; Step 2, add an organic semiconductor material precursor solution on the substrate. The organic semiconductor material precursor solution is distributed in an array on the substrate, and its position corresponds to the pore space position of the porous array template; so that the organic semiconductor material precursor solution can enter the pore space. Step 3, cover the porous array template obtained in Step 1 on the substrate, so that the organic semiconductor material precursor solution enters the pore space of the porous array template; which is convenient for restricting the distribution position of the later semiconductor material. Step 4, after the solvent in the organic semiconductor material precursor solution volatilizes autonomously, remove the porous array template to obtain the organic single crystal microdisk array. The whole process does not require heating or pressurization, has low requirements for preparation equipment and environment, and can obtain crystals with uniform orientation and size.

[0006] As a preferred technical solution of the present invention, in Step 1, the steps for preparing the porous array template are as follows: Step 11: Prepare a columnar microstructure array on a silicon-based substrate as the master template. Step 12: Spin-coat a PDMS colloid on the surface of the master template; for the transfer operation in this step, a material with hot-melt adhesive properties is required to transfer the microstructures on the master template; the PDMS template has the advantages of being easy to prepare, elastic, and having good adhesion to the substrate.

[0007] Step 13: Dry the master template spin-coated with the PDMS colloid. Step 14: After the PDMS colloid is completely cured, remove it from the master template and invert it to obtain a pore array template with a structure opposite to that of the master template. The pore array template obtained by this method has a uniform and controllable pore space distribution size and can be reused.

[0008] As a preferred technical solution of the present invention, in the step 11, a columnar microstructure array is prepared on the silicon-based substrate by a photolithography process.

[0009] As a preferred technical solution of the present invention, in the step 2, the substrate is a silicon-based substrate, a silica substrate, or a glass substrate that has been subjected to a hydrophobic treatment. The hydrophobic treatment facilitates the evaporation of the solvent in the later stage.

[0010] As a preferred technical solution of the present invention, the hydrophobic treatment is to form a layer of trichloro(1H,1H,2H,2H-perfluorooctyl)silane on the surface of the substrate by a gas-phase method.

[0011] As a preferred technical solution of the present invention, in the step 2, the preparation method of the organic semiconductor material precursor solution is to dissolve a 2-hydroxyphenylpropanone derivative in a good solvent, and after fully dissolving, add twice the amount of a poor solvent and mix evenly.

[0012] As a preferred technical solution of the present invention, in the step 3, the organic semiconductor material precursor solution fills the pore space of the pore array template.

[0013] The present invention also discloses a whispering gallery mode microcavity laser using the organic single crystal microdisk array.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: By prefabricating a porous array template, then covering the template on a substrate with an organic semiconductor material precursor solution and allowing the precursor solution to enter the porous space, and finally volatilizing the solvent in the organic semiconductor material precursor solution, after removing the PDMS template, an organic single crystal circular microdisk array is obtained. It realizes the precise positioning and controllable morphology of the crystal structure, precisely regulates the position, size and shape of crystal nucleation, the organic single crystal circular microdisk array exhibits excellent crystallinity and crystal orientation, and makes the solvent volatilization of the organic semiconductor material precursor solution more efficient, providing a simple method for preparing the organic single crystal microdisk array and greatly reducing the time cost; after preparing the reusable porous array template, subsequent operations do not require heating or pressurization, the operation process is simple, and the requirements for the preparation environment and equipment are relatively low.

[0015] Furthermore, the construction method of the organic single crystal microdisk array disclosed in the present invention has high compatibility with the preparation processes of traditional devices, and is of great significance for exploring the low-cost development of high-quality microcavity lasers and large-area device arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the synthesis route of the organic semiconductor material 2-hydroxyacetophenone derivative used in the present invention; Figure 2 Schematic diagram of the growth process of the organic single crystal microdisk array of the present invention; Figure 3 Scanning electron microscope image of the organic single crystal circular microdisk array of the present invention; Figure 4 Fluorescence microscope image of the organic single crystal circular microdisk array of the present invention; Figure 5 Transmission electron microscope image of the organic single crystal circular microdisk array of the present invention; Figure 6 X-ray diffraction pattern of the organic single crystal circular microdisk array of the present invention; Figure 7 Photoluminescence spectrum of a single micro-laser in the organic single crystal circular microdisk array of the present invention under different pump powers; Figure 8 Trend chart of the change in laser emission intensity and full width at half maximum with the change of pump power of a single micro-laser in the organic single crystal circular microdisk array of the present invention; Figure 9 Photoluminescence spectrum of multiple micro-lasers in the organic single crystal circular microdisk array of the present invention; Figure 10 Laser threshold distribution chart of multiple micro-lasers in the organic single crystal circular microdisk array of the present invention. Detailed implementation mode

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention. Embodiment 1

[0018] This embodiment first discloses an organic single crystal microdisk array. The technical solution adopted is that its construction method includes the following steps: Step 1, prepare a photoresist cylindrical microstructural array on a glass substrate through ultraviolet lithography technology; Take a glass substrate with a size of 10 mm × 10 mm, ultrasonically clean it with deionized water, acetone, and alcohol in sequence for 30 minutes, and then dry it with nitrogen. The purpose of this process is to remove foreign substances attached to the glass substrate. Fix the cleaned glass substrate on a spin coater, spin-coat SU-1818 photoresist on the glass substrate at a speed of 1600 r / s, then place the substrate in an oven at 85 °C, take it out after 35 minutes and let it cool to room temperature. Cover the surface of the photoresist film with a mask plate for ultraviolet lithography (the mask plate has a pattern corresponding to the organic single crystal circular microdisk array to be prepared), dissolve the exposed part in the developer, then rinse it with deionized water and dry it with nitrogen, and a main template with a cylindrical array structure will be obtained; Step 2, transfer the photoresist microstructure on the main template; Place the PDMS (polydimethylsiloxane) prepolymer and the supporting thermal curing agent in a container at a weight ratio of 10:1, mix them evenly with a stirring rod, and then put them into an ultrasonic cleaner to remove air bubbles through vibration to obtain a PDMS colloid. Take an appropriate amount of the PDMS colloid and spin-coat it on the main template obtained in Step 1 at a speed of 300 r / s. After baking at 90 °C for 90 minutes, gently peel the formed PDMS colloid from the main template and invert it to prevent the structured side from being contaminated, obtaining a PDMS pore-like array template. The remaining uncured PDMS colloid can be spin-coated on the main template to continue forming.

[0019] The PDMS pore-like array template has a cylindrical pore-like spatial structure with multiple rows and multiple columns arranged in an array and a diameter of 20 μm; Step 3, clean and pre-treat the substrate; First, clean the substrate of the glass substrate: ultrasonically clean it with acetone and alcohol in sequence for 30 minutes, and then dry it with nitrogen; Next, a hydrophobic layer of silane molecules: trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FOTS) was formed on the substrate by chemical vapor deposition; Step 4, prepare the precursor solution of the organic semiconductor material; First, 10 mg of 2-hydroxyphenylpropanone derivative (synthesis route as Figure 1 shown) was dissolved in 50 μL of N,N-dimethylformamide (DMF), shaken until fully dissolved, and then 100 μL of methanol was added as the poor solvent. After mixing evenly, the precursor solution of the organic semiconductor material was obtained; Step 5, growth of the organic single crystal microdisk array; As Figure 2 shown, the precursor solution of the organic semiconductor material was dropped on the substrate. After the solution diffused slightly, the porous array template was covered on the precursor solution of the organic semiconductor material, and a gentle pressure was applied to the back of the template to make the template fit tightly with the substrate. The template and the substrate could fit together automatically by gently pressing the porous array template with fingers. The precursor solution of the organic semiconductor material entered the pore space of the porous array template under the action of capillary force. The pressure applied by the finger should not be too large, otherwise the pore space would collapse downward; Step 6, crystallization; Wait for the solvent in the precursor solution of the organic semiconductor material to volatilize spontaneously. During this process, due to the confinement of the porous array template, the positions of nucleation and crystallization can only be limited within the pore space. After the solvent has completely volatilized, the crystallization is completed. The porous array template is removed, and finally an organic single crystal circular microdisk array is obtained.

[0020] To accelerate the volatilization rate of the solvent in Step 6, the template-solution-substrate sandwich system can be placed on a heating stage at a temperature of 35 °C (if the temperature is too high, the solvent volatilizes too fast, affecting the crystallization effect; if the temperature is too low, the solvent volatilizes too slowly). After about twenty to thirty minutes, the solvent can completely volatilize.

[0021] The morphology of the prepared organic single crystal circular microdisk array was characterized. As Figure 3 shown is the scanning electron microscope image of the organic single crystal circular microdisk array. It can be seen that the surface of the organic single crystal circular microdisk array is flat, the morphology is regular, and an obvious disk structure is presented. The smooth edges and regular morphology of the microdisks allow good optical confinement inside them. Figure 4 is the fluorescence microscope image of the organic single crystal circular microdisk array. It can be seen that under the excitation of an ultraviolet light source, the crystal exhibits strong green fluorescence, and the fluorescence intensity inside the crystal is significantly weaker than that in the edge region, showing obvious self-waveguide emission behavior, which is a prerequisite for having the property of amplified spontaneous emission or generating laser.

[0022] The prepared organic single-crystal circular microdisk arrays were characterized by transmission electron microscopy and X-ray diffraction. As Figure 5 shown, transmission electron microscopy combined with selected area electron diffraction verified the single-crystal nature of the arrays. The bright spots on the selected area electron diffraction pattern indicate a high degree of crystallinity of the organic single-crystal circular microdisk arrays. As Figure 6 shown, the assembled microcrystals have a series of characteristic peaks. The powder of the organic semiconductor material is a polycrystalline mixture, and there are many diffraction peaks on its X-ray diffraction pattern, which proves the single-crystal nature of the prepared organic single-crystal circular microdisk arrays.

[0023] This embodiment also discloses a whispering-gallery mode microcavity laser prepared by using the above-prepared organic single-crystal circular microdisk arrays. The specific process is as follows: A pulsed laser with a wavelength of 355 nm is used to focus into a light spot with a beam diameter of 1 cm to uniformly excite a single circular microdisk.

[0024] The fluorescence properties of the organic single-crystal circular microdisk are characterized by a microarea spectroscopy system. The amplified spontaneous emission behavior and the excited-state dynamic process of the microdisk are studied.

[0025] Figure 7 is the photoluminescence spectrum of the microdisk at different pump densities. At low pump densities, the crystal emits weak fluorescence, and the nearly flat spontaneous emission spectrum dominates the emission spectrum. When the pump density exceeds a certain power threshold, a series of laser emission peaks appear near 530 nm, indicating the presence of fluorescence resonance in the microdisk cavity, which is due to the feedback of the whispering-gallery resonator. As Figure 8 shown, as the pump power further increases, the laser emission intensity increases sharply, and the full width at half maximum (FWHM) decreases accordingly, generating multimode lasers. It shows that a single circular microdisk can be used as an excellent whispering-gallery mode microcavity laser.

[0026] Figure 9 The photoluminescence spectra of six circular microdisks above the threshold were recorded. Obviously, the coherent laser output is concentrated in a relatively narrow spectral range (525 - 532 nm). By comparing the positions of the main peaks, it can be seen that the laser spectral deviation is small, but within a reasonable range. As Figure 10 shown, the laser thresholds of the six circular microdisks are distributed within a certain range, indicating that the organic single-crystal circular microdisk array has good crystal quality and uniform laser performance.

[0027] The whispering-gallery mode resonator has low optical loss and a small mode volume. Through the construction method provided in this application, the integration of miniaturized devices is realized.

[0028] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An organic single crystal microdisk array, characterized in that The construction method thereof comprises the following steps: Step 1, preparing a porous array template; Step 2, adding an organic semiconductor material precursor solution on a substrate, the organic semiconductor material precursor solution being arrayed on the substrate, and the positions corresponding to the pore spatial positions of the porous array template; Step 3, covering the porous array template obtained in Step 1 on the substrate to enable the organic semiconductor material precursor solution to enter the pore spaces of the porous array template; Step 4, after the solvent in the organic semiconductor material precursor solution volatilizes, removing the porous array template, and an organic single crystal microdisk array can be obtained.

2. The organic single crystal microdisk array according to claim 1, wherein, In the said Step 1, the steps of preparing the porous array template are as follows: Step 11, preparing a columnar microstructure array on a silicon-based substrate as a main template; Step 12, spin-coating a PDMS colloid on the surface of the main template; Step 13, drying the main template spin-coated with the PDMS colloid; Step 14, after the PDMS colloid is completely cured, taking it off the main template and inverting it to obtain a porous array template with a structure opposite to that of the main template.

3. The organic single crystal microdisk array according to claim 2, characterized in that: In the said Step 11, a columnar microstructure array is prepared on the silicon-based substrate by a photolithography process.

4. The organic single crystal microdisk array according to claim 1, wherein: In the said Step 2, the substrate is a silicon-based substrate, a silica substrate or a glass substrate that has been subjected to a hydrophobic treatment.

5. The organic single crystal microdisk array according to claim 4, wherein: The hydrophobic treatment is to form a layer of trichloro(1H,1H,2H,2H-perfluorooctyl)silane on the surface of the substrate by a gas-phase method.

6. The organic single crystal microdisk array according to claim 1, characterized in that: In the said Step 2, the preparation method of the organic semiconductor material precursor solution is to dissolve a 2-hydroxyphenylpropiophenone derivative in a good solvent, and after fully dissolving, adding twice the amount of a poor solvent and mixing evenly.

7. The organic single crystal microdisk array according to claim 1, wherein: In the said Step 3, the pore spaces of the porous array template are filled with the organic semiconductor material precursor solution.

8. An optical whispering gallery mode microcavity laser, characterized in that: Irradiate the organic single crystal microdisk array as claimed in claim 1 with a pulsed laser.

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