Method for processing microcavity array by femtosecond laser

Abstract

The invention discloses a method for processing a microcavity array through femtosecond laser, and relates to the field of optical microcavities, and the method comprises the following steps: focusing the laser on the surface of a rhodamine-doped polymer film, controlling the laser to process a plurality of microcavities, and forming the microcavity array on the surface of the rhodamine-doped polymer film through the plurality of microcavities. The rhodamine and the polymer are used as carriers of the microcavity, the microcavity array is formed on the film through the femtosecond laser, a rhodamine 6G exciton transition path is regulated and controlled, the fluorescence efficiency and the quantum yield of the substrate film with the microcavity array are improved, and a femtosecond laser processing mode is adopted, so that the quantum efficiency of the substrate film is improved. The machining precision is improved, the heat affected area is reduced, and repeatability is good.

Description

Technical Field

[0001] The present application relates to the field of optical microcavities, and in particular to a method for processing a microcavity array using a femtosecond laser. Background Art

[0002] Optical microcavities can confine and manipulate light with high quality factors in a small volume, and their research has become a trend in advanced sensor and laser applications based on improving light-matter interactions. Microcavities can manipulate spontaneous recombination rates, polariton generation, mode splitting, and Rabi oscillations. Changes in the local light field within a microcavity are also caused by laser irradiation of the microcavity, leading to structural changes in the self-assembled molecules that interact with the microcavity.

[0003] Microcavities have been extensively studied for their confinement mechanisms, which can confine light by total internal reflection, thereby achieving high-quality resonances and producing phenomena that are difficult to observe in conventional optical microcavities. It has made great contributions to the development of cavity quantum electrodynamics, nonlinear optics, quantum optics, and non-Hermitian photonics. The development of manufacturing processes has provided favorable conditions for the production of high-quality microcavities. Photolithography, self-assembly, electrospinning, and other methods have been used to produce microcavities. However, direct contact processing techniques are easily affected by the materials and processing environment, resulting in poor repeatability.

[0004] Rhodamine molecules are cationic xanthene dyes that have advantages over other dye molecules in terms of fluorescence quantum yield, fluorescence lifetime and fluorescence stability. They are widely used in bio-labeling and fluorescence imaging, and are used as photon media to manufacture hybrid organic photonic devices. However, the self-assembly aggregation of rhodamine molecules occurs in solution or solid. According to the exciton theory, the dipole interaction of single molecules in the aggregated state can split the absorption bands of the two monomers, and the formation of new absorption bands can change the spectral characteristics of the dimer, which will greatly reduce the fluorescence efficiency and quantum yield of the dye molecules. Summary of the invention

[0005] In view of the deficiencies of the above-mentioned related technologies, the present application provides a method for processing a microcavity array by femtosecond laser. The present application uses rhodamine and polymer as carriers of the microcavity, forms a microcavity array on a film by femtosecond laser, regulates the exciton transition path of rhodamine 6G, improves the fluorescence efficiency and quantum yield of the substrate film processed with the microcavity array, and adopts the femtosecond laser processing method to improve the processing accuracy, reduce the heat-affected area and have good repeatability.

[0006] In the first aspect, the present application provides a method for processing a microcavity array using a femtosecond laser, which adopts the following technical solution: A method for processing a microcavity array using a femtosecond laser comprises the following steps: focusing laser light on the surface of a rhodamine-doped polymer film and controlling the laser light to process a plurality of microcavities, wherein the plurality of microcavities form a microcavity array on the surface of the rhodamine-doped polymer film.

[0007] Preferably, the spacing between adjacent microcavities in the microcavity array is 2-10 μm, and the microcavity is disc-shaped.

[0008] Preferably, the spacing between adjacent microcavities in the microcavity array is 5 μm, and the microcavity is disc-shaped.

[0009] Preferably, the microcavity has a diameter of 5-35 μm and a depth of 500-1000 nm.

[0010] Preferably, the microcavity has a diameter of 10-20 μm and a depth of 800 nm.

[0011] Preferably, the polymer used in the rhodamine-doped polymer film is one or more of polymethyl methacrylate, polystyrene, and polyvinyl alcohol.

[0012] Preferably, the polymer used in the rhodamine-doped polymer film is polymethyl methacrylate.

[0013] Preferably, the rhodamine used in the rhodamine-doped polymer film is one or more of rhodamine 6G, rhodamine B, and rhodamine 123.

[0014] Preferably, the rhodamine used in the rhodamine-doped polymer film is rhodamine 6G.

[0015] Preferably, the rhodamine-doped polymer film is prepared by the following steps: dissolving rhodamine and a polymer in a solvent to obtain a mixed solution, preparing the mixed solution into a film, and annealing to obtain the rhodamine-doped polymer film.

[0016] Preferably, the weight ratio of the rhodamine to the polymer is 1:8-15.

[0017] Preferably, the weight ratio of the rhodamine to the polymer is 1:10.

[0018] Preferably, the film is prepared by drop coating, and the specific process is: while increasing the rotation speed of the substrate of the spin coater from 800-1200rmp / s to 4000rmp / s at an acceleration of 2000rmp / s, drip the mixed solution onto the substrate for spin coating, and then maintain the rotation speed at 4000rmp / s for 20-40s.

[0019] Preferably, the film is prepared by drop coating, and the specific process is: while increasing the rotation speed of the substrate of the spin coater from 1000 rpm to 4000 rpm at an acceleration of 2000 rpm / s, drip the mixed solution onto the substrate for spin coating, and then maintain the rotation speed at 4000 rpm / s for 30 seconds.

[0020] Preferably, the annealing temperature is 90-110° C. and the time is 3-8 min.

[0021] Preferably, the annealing temperature is 100° C. and the time is 5 min.

[0022] In the second aspect, the present application provides a microcavity array using the following technical solution: A microcavity array is obtained by processing the microcavity array using a femtosecond laser.

[0023] In a third aspect, the present application provides a system for processing a microcavity array using a femtosecond laser, which adopts the following technical solution: A system for processing a microcavity array by femtosecond laser comprises a femtosecond laser for generating laser light, a harmonic regenerator for adjusting the laser wavelength, a two-dimensional energy attenuator for controlling the laser energy density and an electric stage for placing a rhodamine-doped polymer film, which are arranged in sequence. The femtosecond laser, the harmonic regenerator and the two-dimensional energy attenuator are optically connected, and a focusing lens for focusing the laser light on the rhodamine-doped polymer film is arranged between the two-dimensional energy attenuator and the electric stage.

[0024] Preferably, the wavelength of the laser generated by the femtosecond laser is 1026 nm, the repetition frequency is 200 kHz, the output power is 200 mW and the pulse width is 190 fs.

[0025] In summary, the present application includes at least one of the following beneficial technical effects: 1. The present application uses rhodamine and polymer as a base film, forms a microcavity array thereon, regulates the exciton transition path of rhodamine 6G, effectively reduces the exciton transfer from monomer molecules to dimer molecules of rhodamine 6G molecules, and thus improves the fluorescence efficiency and quantum yield of the base film formed with the microcavity array.

[0026] 2. This application uses femtosecond laser to process microcavity arrays on thin films, with high processing accuracy, small heat-affected area, and good repeatability; 3. The femtosecond laser processing microcavity array system of the present application controls the wavelength and laser energy density of the laser, and processes microcavities on a thin film to form a microcavity array through an electric stage, thereby improving the accuracy and efficiency of processing the microcavity array. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the overall structure of the system for femtosecond laser processing of microcavity arrays in the present application.

[0028] Figure 2 This is a diagram of the preparation process of the femtosecond laser processed microcavity array of the present application; Figure 3 It is a comparison diagram of optical microscope images of a disk microcavity array on the surface of a rhodamine-doped PMMA film processed by the method for processing a microcavity array with a femtosecond laser in Examples 2-7 of the present application; Figure 4 is a spectrum of a disk microcavity array on the surface of a rhodamine-doped PMMA film processed by the femtosecond laser processing microcavity array method of Example 2-7 and a rhodamine-doped PMMA film (Film) without processing the disk microcavity array, wherein Figure 4 (a) is the UV absorption spectrum. Figure 4 (b) is the fluorescence spectrum. Figure 4 (c) is the white light spectrum; Figure 5 The transient absorption spectra of the disk microcavity array on the surface of the rhodamine-doped PMMA film without processing the disk microcavity array and the disk microcavity array processed by the femtosecond laser processing microcavity array method of Examples 2-4; Figure 6 It is a global analysis diagram of the transient absorption spectra of the disk microcavity array on the surface of the rhodamine-doped PMMA film without processing the disk microcavity array and the disk microcavity array processed by the femtosecond laser processing microcavity array method of Example 2.

[0029] Figure numerals: 1. femtosecond laser; 2. harmonic generator; 3. two-dimensional energy attenuator; 4. polarization rotation mirror; 5. first reflector; 6. first beam splitter; 7. laser galvanometer scanning system; 8. spatial light modulator; 9. first dichroic mirror; 10. second dichroic mirror; 11. second beam splitter; 12. CCD camera; 13. LED light source; 14. focusing objective lens; 15. electric stage; 16. marble substrate. DETAILED DESCRIPTION

[0030] The present application is further described in detail below in conjunction with examples. The following examples are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. In the following examples, if specific conditions are not specified, they are carried out according to normal conditions or conditions recommended by the manufacturer. The methods used are conventional methods known in the art unless otherwise specified, and the consumables and reagents used are commercially available unless otherwise specified. Unless otherwise specified, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the recorded content may also be applied to the present invention.

[0031] The raw materials used in the examples and comparative examples can all be obtained commercially.

[0032] Example 1 Embodiment 1 of the present application provides a system for processing a microcavity array using a femtosecond laser.

[0033] Reference Figure 1 A system for processing a microcavity array with a femtosecond laser comprises a femtosecond laser, a harmonic generator, a two-dimensional energy attenuator, a polarization rotator, a first reflector, a first beam splitter, a laser galvanometer scanning system, a spatial light modulator, a first dichroic mirror, a second dichroic mirror, a second beam splitter, a CCD camera, an LED light source, a focusing objective lens, an electric stage and a marble substrate, and the components are optically connected. The preset femtosecond laser is output by the femtosecond laser, and the light of 1026nm wavelength is frequency-doubled to 513nm by the harmonic generator, and the laser energy is attenuated to 10% of the original energy by the two-dimensional energy attenuator, and then enters the laser galvanometer scanning system and the spatial light modulator after passing through the first reflector and the first beam splitter, and then the laser passes through the second dichroic mirror and is focused on the electric stage through a 50x objective lens. At the same time, the CCD camera 12 and the CCD LED light 13 work simultaneously, which are used for auxiliary adjustment and real-time monitoring, and are not used for sample processing.

[0034] Among them, the femtosecond laser light source: uses ytterbium-doped potassium gadolinium tungstate (Yb:KGW) as the gain medium, the laser output wavelength is 1026nm, the pulse width is 190fs, the maximum power can reach 10W, and the repetition frequency is 200kHz.

[0035] Harmonic generator: This system can double and triple the frequency of 1026nm femtosecond laser to generate second harmonic with a wavelength of 515nm, and its conversion efficiency is 50%.

[0036] Two-dimensional energy attenuator: It is composed of adjustable filters and can adjust the laser energy by adjusting the transmission path of the light beam.

[0037] The polarization rotator is a half-wave plate, which is used to adjust the polarization state of the femtosecond laser beam.

[0038] The first reflecting mirror, the first beam splitter, the first dichroic mirror, the second dichroic mirror and the second beam splitter are all used to adjust the direction of the laser light path.

[0039] Laser galvanometer scanning system: adjust the laser optical path through the interaction of two mirrors.

[0040] Spatial light modulator: used to shape the laser beam.

[0041] CCD camera is a charge coupled device, which is used to collect image information.

[0042] LED light source uses white light emitted by LED lamps for field observation.

[0043] The focusing objective lens is used for focusing, and a 50x magnification lens with a numerical aperture of 0.42 is used to focus the 513nm wavelength laser to 1μm.

[0044] The marble substrate is used to carry the above-mentioned components and improve the safety and stability of laser processing.

[0045] Example 2 Embodiment 2 of the present application provides a method for processing a microcavity array using a femtosecond laser, referring to Figure 2 The schematic diagram of the preparation process is shown in the following steps: a quartz plate is ultrasonically cleaned in deionized water, ethanol, isopropanol and acetone for 15 minutes respectively, and then blown dry with a nitrogen gun for use. 5 mg of rhodamine 6G powder and 50 mg of PMMA are weighed and dissolved in 1 mL of dichloromethane, stirred at room temperature for 2 hours, and then filtered using a 0.45 µm oily filter to obtain a mixed solution. The mixed solution is used to prepare a thin film by drop coating. The substrate of the spin coater is increased from 1000 rpm / s to 4000 rpm / s at an acceleration of 2000 rpm / s, and the mixed solution is dripped onto the substrate for spin coating, and then maintained at 4000 rpm / s for 30 seconds. Finally, the spin-coated sample is heated on a hot plate at 100 ° C for 5 minutes to remove the residual solvent in the film to obtain a rhodamine-doped PMMA film. The rhodamine-doped PMMA film was placed on a motorized stage in a femtosecond laser processing microcavity array system and fixed. A disk microcavity was processed on the rhodamine-doped PMMA film by the femtosecond laser processing system to form a disk microcavity array. The diameter of the disk microcavity was 10 μm, the depth was 800 nm, and the interval between two adjacent disk microcavities was 5 μm.

[0046] In this embodiment, the laser wavelength generated by the femtosecond laser is 1026nm, the repetition frequency is 200kHz, the output power is 200mW, the pulse width is 190fs, the wavelength of the laser is converted to 513nm by a harmonic generator, the laser energy is attenuated to 10% of the original energy by a two-dimensional energy attenuator, and enters the laser galvanometer scanning system and the spatial light modulator after passing through the first reflector and the first beam splitter. Then the laser passes through the second dichroic mirror and is focused to the surface of the film through a 50x objective lens. The spot diameter is 1μm, and the movement speed is controlled to be 0.03mm / s by controlling the movement of the electric stage.

[0047] Example 3 Embodiment 3 of the present application provides a method for processing a microcavity array using a femtosecond laser. The difference between Embodiment 3 and Embodiment 2 is that the diameter of the disk microcavity processed in Embodiment 3 is 15 μm.

[0048] Example 4 Example 4 of the present application provides a method for processing a microcavity array using a femtosecond laser. The difference between Example 4 and Example 2 is that the diameter of the disk microcavity processed in Example 4 is 20 μm.

[0049] Example 5 Example 5 of the present application provides a method for processing a microcavity array using a femtosecond laser. The difference between Example 5 and Example 2 is that the diameter of the disk microcavity processed in Example 5 is 25 μm.

[0050] Example 6 Example 6 of the present application provides a method for processing a microcavity array using a femtosecond laser. The difference between Example 6 and Example 2 is that the diameter of the disk microcavity processed in Example 6 is 30 μm.

[0051] Example 7 Example 7 of the present application provides a method for processing a microcavity array using a femtosecond laser. The difference between Example 7 and Example 2 is that the diameter of the disk microcavity processed in Example 7 is 35 μm.

[0052] Test and Inspection An optical microscope was used to image the surface of the PMMA film doped with rhodamine processed by the femtosecond laser processing method of the microcavity array of Example 2-7, and a comparison diagram of the optical microscope image of the disk microcavity array was obtained as shown in FIG. Figure 3 The disk microcavity array on the surface of the rhodamine-doped PMMA film processed by the femtosecond laser processing microcavity array method of Example 2-7 and the rhodamine-doped PMMA film (Film) without the disk microcavity array were subjected to spectral testing. The test results are shown in FIG. Figure 4 As shown, Figure 4 (a) is the UV absorption spectrum. Figure 4(b) is the fluorescence spectrum. Figure 4 (c) is a white light spectrum. Transient absorption spectroscopy was performed on the PMMA film doped with rhodamine without processing the disk microcavity array and the disk microcavity array on the surface of the PMMA film doped with rhodamine processed by the femtosecond laser processing microcavity array method of Example 2-4. The results are shown in FIG. Figure 5 As shown, press Figure 5 (a)-(d) arrangement. A global analysis of the transient absorption spectra of the disk microcavity array on the surface of the rhodamine-doped PMMA film without the disk microcavity array and the disk microcavity array on the surface of the rhodamine-doped PMMA film processed by the femtosecond laser processing microcavity array method of Example 2 was performed. The sequential model was used to obtain the evolution correlation difference spectrum (EADS) as shown in FIG. Figure 6 As shown, press Figure 6 (a)-(b) Arrangement. Result analysis The following combination Figure 3-6 The experimental results provided are used to explain this application in detail.

[0053] Reference Figure 3 The disk microcavity array on the surface of the rhodamine-doped PMMA film processed by the method of femtosecond laser processing microcavity array in Example 2-7 has neat arrangement of the disk microcavity array, a surface roughness of less than 0.4 μm, a regular disk edge morphology, and no cracks or molten residues. The disk microcavity array on the surface of the rhodamine-doped PMMA film processed by femtosecond laser has high completion and good repeatability.

[0054] Reference Figure 4 ,like Figure 4 As shown in the ultraviolet absorption spectrum of (a), the shoulder peak at 500nm blue-shifts as the diameter of the microdisk decreases. This blue-shift may be attributed to the characteristics of the H-type rhodamine 6G dimer, and there are some rhodamine 6G molecular aggregates in PMMA. The absorption of the disk microcavity array on the surface of the rhodamine-doped PMMA film processed by the femtosecond laser processing microcavity array method of Example 2-7 is enhanced in the range of 570nm to 700nm compared with the rhodamine-doped PMMA film sample, and the absorption intensity further increases as the diameter of the microdisk decreases. Figure 4 As shown in the fluorescence spectrum of (b), as the diameter of the disk microcavity decreases, the fluorescence spectrum shows a blue shift trend, such as Figure 4 (c) shows the white light spectrum, indicating that the blue shift of the absorption spectrum is not caused by the interference effect of the disk microcavity array.

[0055] Reference Figure 5The negative absorption band observed at 530 nm corresponds to the bleaching of the monomer absorption band and the associated stimulated emission, which is consistent with the initial fluorescence spectrum. This negative absorption band leads to the initial transient absorption of the film and disk microcavity array. As the diameter of the disk microcavity decreases, the shoulder peak blue-shifts. In the disk microcavity array with a diameter of 10 µm, the shoulder peak is located at 480 nm, which is consistent with the initial fluorescence spectrum. Figure 4 (a) is consistent with the blue shift of the shoulder peak in the ultraviolet absorption spectrum, indicating that the reduction of the microcavity diameter leads to the blue shift of the shoulder peak. In addition, the excited state absorption (ESA) signal changes in the transient absorption spectrum of the disk microcavity array. Specifically, the wavelength of the excited state absorption signal blue-shifts from 614nm for the 20µm diameter microcavity array to 569nm for the 10µm microcavity array, showing a trend of blue shift as the disk microcavity diameter decreases.

[0056] Reference Figure 6 , Figure 6 The peak at 498 nm in (a) showed almost no decay within 75.7 ps. However, the peak at 530 nm decreased significantly, which may be due to the transfer of electrons from monomers to dimers. Figure 6 (b) In the global analysis of the 10μm disk microcavity array, the peak centers at 480nm and 530nm show the same downward trend with the increase of delay time. It is speculated that the presence of the microcavity enhances the internal electric field, resulting in the change of the molecular excited state and raising the energy level of the Rhodamine 6G dimer. This may increase the barrier between the energy levels of the Rhodamine 6G monomer and dimer, thereby hindering electron transfer. This also explains the change in the relative intensity of the main peak and the shoulder peak. In addition, compared with the transient absorption spectrum in the Rhodamine-doped PMMA film sample without processing the disk microcavity array, Figure 6 (b) A positive intensity excited state absorption signal was observed in the 560-700nm band. As mentioned above, this is attributed to the resonance of the light emitted by the Rhodamine 6G molecule under the interaction with the microcavity, thereby enhancing the state density of the exciton. Therefore, the Rhodamine 6G doped PMMA microcavity array processed by femtosecond laser realizes the regulation of the Rhodamine 6G exciton transition path, effectively reducing the exciton transfer from the monomer molecule of the Rhodamine 6G molecule to the dimer molecule. Since the exciton transfer from the monomer molecule to the dimer molecule will significantly reduce the fluorescence efficiency and quantum yield of Rhodamine 6G, the use of the disk microcavity array on the surface of the Rhodamine-doped PMMA film processed by the femtosecond laser processing microcavity array method of Example 2 to make optical devices is conducive to improving the fluorescence efficiency and quantum yield of optical devices.

[0057] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make modifications to the present embodiment without any creative contribution as needed. However, as long as it is within the scope of the claims of the present application, it shall be protected by the patent law.

Claims

1. A method for processing a microcavity array using a femtosecond laser, characterized in that: The method comprises the following steps: focusing laser on the surface of rhodamine-doped polymer film and controlling the laser to process a plurality of microcavities, wherein the plurality of microcavities form a microcavity array on the surface of the rhodamine-doped polymer film.

2. The method for processing a microcavity array using a femtosecond laser according to claim 1, characterized in that: The spacing between adjacent microcavities in the microcavity array is 2-10 μm, and the microcavity is disc-shaped.

3. The method for processing a microcavity array using a femtosecond laser according to claim 1, characterized in that: The microcavity has a diameter of 5-35 μm and a depth of 500-1000 nm.

4. The method for processing a microcavity array using a femtosecond laser according to claim 1, characterized in that: The polymer used in the rhodamine-doped polymer film is one or more of polymethyl methacrylate, polystyrene and polyvinyl alcohol.

5. The method for processing a microcavity array using a femtosecond laser according to claim 1, characterized in that: The rhodamine-doped polymer film is prepared by the following steps: dissolving rhodamine and a polymer in a solvent to obtain a mixed solution, preparing the mixed solution into a film, and annealing to obtain the rhodamine-doped polymer film.

6. The method for processing a microcavity array using a femtosecond laser according to claim 5, characterized in that: The weight ratio of the rhodamine to the polymer is 1:8-15.

7. The method for processing a microcavity array using a femtosecond laser according to claim 5, characterized in that: The film is prepared by drop coating, and the specific process is: the substrate of the spin coater is increased from 800-1200rmp / s to 4000rmp / s at an acceleration of 2000rmp / s, the mixed solution is dripped onto the substrate for spin coating, and then the rotation speed is maintained at 4000rmp / s for 20-40s.

8. The method for processing a microcavity array using a femtosecond laser according to claim 5, characterized in that: The annealing temperature is 90-110° C. and the annealing time is 3-8 min.

9. A microcavity array, characterized in that: The microcavity array is obtained by processing using a femtosecond laser processing microcavity array method according to any one of claims 1 to 8.

10. A system for processing a microcavity array using a femtosecond laser according to any one of claims 1 to 8, characterized in that: The invention comprises a femtosecond laser for generating laser light, a harmonic regenerator for adjusting the laser wavelength, a two-dimensional energy attenuator for controlling the laser energy density and an electric stage for placing a rhodamine-doped polymer film, which are arranged in sequence. The femtosecond laser, the harmonic regenerator and the two-dimensional energy attenuator are optically connected, and a focusing lens for focusing the laser light on the rhodamine-doped polymer film is arranged between the two-dimensional energy attenuator and the electric stage.

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