A flexible transferable vortex laser device for generating a vortex laser and a method of manufacture

Abstract

This invention discloses a flexible, transferable vortex laser device and its fabrication method. A two-dimensional grating periodic structure is obtained using a two-beam interferometry exposure technique. A mixed solution of polymer material MDMO-PPV and toluene solution is selected as the gain material to fabricate the vortex laser device. The fabricated device is then immersed in a developer to remove all photoresist from a glass substrate. This results in a flexible, transferable vortex laser device, promoting the wider application of vortex beams in daily life and production.

Description

Technical Field

[0001] This invention relates to the field of generating vortex lasers, and more specifically to a simple, efficient, flexible, and transferable method for fabricating a vortex laser device. Background Technology

[0002] Vortex beams are structured beams with helical wavefronts carrying orbital angular momentum, and they have wide applications in optical data transmission, optical tweezers, quantum entanglement, and super-resolution imaging. Generating high-performance vortex beams is crucial for these advanced applications. Initially, vortex beams were generated using helical phase plates, followed by the use of spatial light modulators to directly control the amplitude or phase of the optical field. Later, metasurfaces were proposed to improve the quality of vortex beams. However, due to the low purity of spatial modes, passively generating optical vortex beams using bulky or planar discrete elements encounters a low signal-to-noise ratio problem, which is critical and unavoidable in many applications. Therefore, developing a simple and efficient method for generating vortex beams has become an urgent need in practical applications.

[0003] To address this issue, researchers have recently proposed methods for actively generating vortex beams, such as generating vortex beams based on traditional laser cavities, and later, generating vortex beams based on laser microcavities. However, the inherent characteristics of whispering-gallery microcavities hinder the fabrication of flexible, ultrathin lasers. Continuous-domain bound-state (BIC) vortex lasers have attracted widespread attention due to their ultra-high quality factor, enabling low-threshold emission vortex lasers. However, current research has not yet proposed flexible, transferable applications based on BIC vortex lasers.

[0004] Two-beam interference lithography (BIC) is a technique that records an interference pattern composed of two coherent light waves onto a photoresist recording layer. This interference pattern consists of a periodic sequence of fringes, representing the maximum and minimum intensities, respectively. During the post-exposure lithography process, a photoresist pattern corresponding to this periodically changing intensity pattern emerges. The technique used to fabricate the grating is interference holography. The grating period is defined by the formula Λ = λ / 2sinθ, where Λ is the grating period, λ is the wavelength of the interference source, and θ is half the angle between the two interference beams. When constructing the interference optical path, the grating period can be accurately controlled by adjusting the angle between the two interference beams. A two-dimensional photonic crystal grating structure can be obtained through double exposure with a 90° rotation. BICs can be generated within a two-dimensional photonic crystal microcavity. Based on the characteristics of BICs, generating vortex beams using a two-dimensional photonic crystal microcavity is an efficient fabrication method. This technique is low-cost, simple, and easy to operate, and it plays a positive role in promoting the fabrication of vortex laser devices. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a flexible, transferable vortex laser device that uses a simple and efficient fabrication technique to enable the vortex laser to generate stable and minimally lossy vortex lasers under femtosecond laser excitation.

[0006] The technical solution adopted to achieve the purpose of this invention is:

[0007] A method for fabricating a flexible, transferable vortex laser device includes the following steps:

[0008] Step 1: Clean the glass substrate (1.5cm × 1.5cm) twice with anhydrous ethanol using ultrasonic cleaning, 30 minutes each time, and then dry it thoroughly.

[0009] Step 2: Spin-coat photoresist (PR, AR-P3170) onto a glass substrate at high speed. After spin-coating, perform heat treatment to form a PR film.

[0010] Step 3: Use a 360nm continuous laser to expose the prepared sample using holographic technology. Utilize the constructed dual-beam interference optical path to expose the sample twice. The first exposure lasts 20 seconds. After the first exposure, rotate the sample 90° for a second exposure, which lasts 20 seconds.

[0011] Step 4: After exposure, place the sample in developer (AR-300-47, Allresistance, Straussberg, Germany) to dissolve the imprinted area. The development time is 15s to obtain a DFB resonant cavity with a grating structure period of 400nm.

[0012] Step 5: The sample with the grating structure is heat-treated for fixation. After the sample cools, a high-speed spin-coating gain material is formed on the grating structure by a mixture of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene](MDMO-PPV, Sigma-Aldrich) and toluene solution at a concentration of 8.5 mg / ml.

[0013] Step 6: Immerse the prepared device in the developer for one hour to dissolve all the PR in the device. After the PR is completely dissolved, a gain film with a grating structure can be obtained;

[0014] Step 7: Use a PET substrate with a circular hole to lift the film, let it air dry, and then pump the gain film with a femtosecond laser to obtain a vortex beam similar to a donut.

[0015] Step 8: Based on step 6, use a clean glass slide or lens to lift the film and let it air dry naturally. Then, pump the gain film with a femtosecond laser to obtain a donut-shaped vortex beam, thus proving the successful fabrication of a flexible transferable vortex laser device.

[0016] In the above technical solution, in step 2, the PR spin coating conditions are high-speed spin coating at 2500 rpm for 30 seconds and heating conditions are heating at 110°C for 1 minute.

[0017] In the above technical solution, in step 3, the power of the 360nm continuous laser is controlled to be 700-800μW during exposure. The period used when constructing the dual-beam interference optical path is defined by the period Λ of the DFB cavity, Λ=λ / 2sinθ, where θ refers to half of the angle between the two interference beams (λ=360nm) (θ=26°).

[0018] In the above technical solution, in step 4, the DFB resonant cavity is prepared by two exposures using a dual-beam interference optical path. After development, the resulting grating structure is similar to a two-dimensional photonic crystal and serves as the laser resonant cavity.

[0019] In the above technical solution, in step 5, the heat treatment conditions are 110°C for 1 minute, and the gain material is prepared by mixing 8.5 mg of MDMO-PPV with 1 ml of toluene solution, resulting in a mixed solution concentration of 8.5 mg / ml. The spin-coating conditions for the gain material are high-speed spin-coating at 2500 rpm for 30 seconds.

[0020] In the above technical solution, step 6, immersing the prepared device in the developer, aims to remove all the PR layer on the glass substrate. Once all the PR has dissolved, the gain film with the grating structure will automatically detach from the glass substrate and float on the surface of the developer. After being retrieved and dried, an ultrathin, flexible, and transferable laser device can be obtained.

[0021] In the above technical solution, in step 7, when the femtosecond laser pumps the laser device, the repetition rate is 1kHz, the pump energy is 90%, and the pump power of the femtosecond laser after passing through the attenuator is 400-500μW.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] 1) The fabrication of the flexible transferable vortex laser device provided by the present invention has low fabrication cost, simple and easy operation, and good repeatability.

[0024] 2) The flexible, transferable vortex laser device provided by this invention can generate efficient and stable vortex lasers under femtosecond laser pumping. Furthermore, the device can be placed on different objects as needed, and can still emit vortex lasers under laser pumping, enhancing the wide application of vortex laser devices in daily life and production.

[0025] 3) The flexible transferable vortex laser device provided by the present invention has excellent comprehensive performance and has important application value in the field of vortex laser generation. Attached Figure Description

[0026] Figure 1 The diagram shows a fabrication process for a flexible, transferable vortex laser device.

[0027] Figure 2 The image shown is an electron scanning microscope image of a grating structure.

[0028] Figure 3 The emission spectrum and threshold of a laser-pumped vortex laser device are shown.

[0029] (a) is the emission spectrum of a laser-pumped vortex laser device;

[0030] (b) is the threshold value of the vortex laser device under laser pumping;

[0031] Figure 4 The image shows the far-field distribution of the laser emitted by the vortex laser device, recorded using a spot analyzer. Detailed Implementation

[0032] The present invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] Implementation Case 1

[0034] A method for fabricating a flexible, transferable vortex laser device includes the following steps:

[0035] Step 1: Clean the glass substrate (1.5cm × 1.5cm) twice with anhydrous ethanol using ultrasonic cleaning, 30 minutes each time, and then dry it thoroughly.

[0036] Step 2: Use a pipette to take 35 μl of photoresist (PR, AR-P3170) and spin coat it onto a clean glass substrate at a speed of 2500 rpm for 30 seconds. After spin coating, heat it on a heating stage at 110°C for 1 minute to form a PR film.

[0037] Step 3: Use a 360nm continuous laser to expose the prepared sample using holographic technology, controlling the power to 700-800μW during exposure. The period used in constructing the dual-beam interference path is defined using the period Λ of the DFB cavity, Λ = λ / 2sinθ, where θ is the angle between the two interference beams (λ = 360nm) (θ = 26°). Using the constructed dual-beam interference path, expose the sample twice. The first exposure lasts 20 seconds. After the first exposure, rotate the sample 90° for a second exposure of 20 seconds.

[0038] Step 4: After exposure, place the sample in developer (AR-300-47, Allresistance, Straussberg, Germany) to dissolve the imprinted area. The development time is 15s. The grating structure obtained after development is similar to a two-dimensional photonic crystal, and a DFB resonant cavity with a grating structure period of 400nm can be obtained.

[0039] Step 5: The sample with the grating structure is heat-treated for fixation. The heating conditions are 110°C for 1 minute. After the sample cools, 50 μl of gain material is spin-coated at 2500 rpm for 30 seconds using a pipette. The gain material is a mixture of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV, Sigma-Aldrich) and toluene solution, prepared by mixing 8.5 mg of MDMO-PPV with 1 ml of toluene solution, resulting in a concentration of 8.5 mg / ml. This forms a gain film on the grating structure.

[0040] Step 6: Immerse the prepared device in the developer for one hour to remove all the PR layer on the glass substrate. Once the PR is completely dissolved, the gain film with the grating structure will automatically detach from the glass substrate and float on the surface of the developer. Remove it and let it dry to obtain an ultrathin, flexible, and transferable laser device.

[0041] Step 7: Use a PET substrate with a circular hole to lift the film and allow it to air dry. Pump the gain film with a femtosecond laser at a repetition rate of 1kHz and a pump energy of 90%. The pump power of the femtosecond laser after passing through the attenuator is 400-500μW. A donut-shaped vortex beam can be obtained.

[0042] Step 8: Based on step 6, use a clean glass slide or lens to lift the film and let it air dry naturally. Then, use a femtosecond laser to pump the gain film with a repetition rate of 1 kHz and a pump energy of 90%. This will produce a vortex beam similar to a donut, thus proving the successful fabrication of a flexible transferable vortex laser device.

[0043] Appendix Figure 3 Figure (a) shows the emission spectrum of the vortex laser device pumped by a femtosecond laser. Two emission peaks are observed near a wavelength of 610 nm, corresponding to two modes of the continuous-domain bound state. As the pump intensity increases, the emission peak intensity of one mode increases, while the emission peak intensity of the other mode gradually stops increasing with increasing pump intensity. Eventually, one mode wins the competition and is represented by a single laser emission peak at a wavelength of 610 nm. Figure (b) shows the threshold of the tested vortex laser device under laser pumping, which is 8.3 μJ / cm². 2 Compared to existing laser devices that generate vortex lasers, this invention has a lower lasing threshold.

[0044] Appendix Figure 4 This is the far-field distribution of the laser emitted by a vortex laser device, recorded using a spot analyzer. Pumping a vortex laser device with a femtosecond laser can produce lasers as shown below. Figure 4 The hollow vortex beam shown is illustrated. By peeling off the film from the device, a flexible, transferable gain film with a grating structure is obtained. This gain film can be placed on a mirror, glass, contact lens, or other objects, and pumped with a femtosecond laser, still emitting vortex laser light. This flexible, transferable vortex laser device significantly reduces manufacturing costs and has a wide range of flexible applications.

[0045] The emitted vortex laser was spectrally measured using a full-band spectrometer, revealing two emission peaks near a wavelength of 610 nm. These peaks showed good agreement with the results calculated using finite element analysis software (COMSOL). This demonstrates that the fabricated vortex laser device is based on vortex lasers generated by BIC (Bipolar Induction Coefficient), thus successfully fabricating a flexible, transferable vortex laser device.

Claims

1. A method for fabricating a flexible, transferable vortex laser device for generating vortex lasers, characterized in that, The method includes the following steps: Step 1: Clean the 1.5cm×1.5cm glass substrate twice with anhydrous ethanol using ultrasonic cleaning, 30 minutes each time, and then dry it thoroughly. Step 2: Spin coat the photoresist PR on the cleaned glass substrate at high speed. The photoresist PR is AR-P3170. After spin coating, heat treatment is performed to form a PR film. Step 3: Use a 360nm continuous laser to expose the prepared PR film using holographic technology, and perform two exposures using a constructed dual-beam interference optical path; the first exposure lasts 20 seconds, and after the first exposure, rotate the PR film 90° for a second exposure, which lasts 20 seconds. Step 4: After exposure, the PR film is placed in developer AR-300-47 to dissolve the imprinted area. The development time is 15s to obtain a DFB resonant cavity with a grating structure period of 400nm, that is, to obtain a sample with a grating structure. Step 5: The sample with the grating structure is heat-treated for fixation; after the sample cools, a high-speed spin-coating of a gain material consisting of a mixture of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene]MDMO-PPV and toluene solution at a concentration of 8.5 mg / ml is used to form a gain film on the grating structure; the prepared device is obtained. Step 6: Immerse the prepared device in the developer for one hour to dissolve all the PR in the device; after the PR is completely dissolved, a gain film with a grating structure is obtained. Step 7: Use a PET substrate with a circular hole to lift the film, let it air dry, and then pump the gain film with a femtosecond laser to obtain a vortex beam similar to a donut. Step 8: Based on step 6, use a clean glass slide or lens to lift the thin film, let it air dry, and then pump the gain film with a femtosecond laser to obtain a donut-shaped vortex beam, thus proving the successful fabrication of a flexible transferable vortex laser device.

2. The method for fabricating a flexible, transferable vortex laser device for generating vortex lasers according to claim 1, characterized in that: In step 2, the PR spin coating conditions are high-speed spin coating at 2500 rpm for 30 seconds and heating conditions are heating at 110°C for 1 minute.

3. The method for fabricating a flexible, transferable vortex laser device for generating vortex lasers according to claim 1, characterized in that: In step 3, the power of the 360nm continuous laser is controlled to be 700-800μW when it is used for exposure; the period used when building the dual-beam interference optical path is defined by the period Λ of the DFB cavity, Λ=λ / 2sinθ, where θ refers to the angle between the two interference beams; the wavelength of the interference beam λ=360nm, and the angle between the interference beams θ=26°.

4. The method for fabricating a flexible, transferable vortex laser device for generating vortex lasers according to claim 1, characterized in that: In step 4, the DFB resonant cavity is prepared by two exposures using a dual-beam interference optical path. After development, the resulting grating structure is similar to a two-dimensional photonic crystal and serves as the laser resonant cavity.

5. The preparation method according to claim 1, characterized in that: In step 5, the heating conditions are 110°C for 1 minute, and the gain material is prepared by mixing 8.5 mg of MDMO-PPV with 1 ml of toluene solution to obtain a mixed solution concentration of 8.5 mg / ml; the spin coating conditions for the gain material are high-speed spin coating at 2500 rpm for 30 seconds.

6. The method for fabricating a flexible, transferable vortex laser device for generating vortex lasers according to claim 1, characterized in that: In step 6, the purpose of immersing the prepared device in the developer is to remove all the PR on the glass substrate. When all the PR has dissolved, the gain film with the grating structure will automatically detach from the glass substrate and float on the surface of the developer. After being picked up and dried, an ultrathin, flexible, and transferable laser device can be obtained.

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