Optical fiber vortex random laser integrated with multi-orbital angular momentum mode, preparation method of optical fiber vortex random laser, and vortex random laser generation device and method

Abstract

The invention provides an optical fiber vortex random laser integrated with a multi-orbital angular momentum mode, a preparation method of the optical fiber vortex random laser, and a vortex random laser generation device and method, and belongs to the technical field of lasers. The problems that the radiation direction of an existing vortex random laser needs to be optimized and the system integration needs to be enhanced are solved. Comprising a microfluid channel, a single-mode optical fiber, an optical fiber splitter and an optical fiber integrated with a spiral phase plate, a gain medium and scattering particles are arranged in the microfluid channel, and one end of the single-mode optical fiber is solidified in the microfluid channel. The other end of the single-mode optical fiber is coupled with the end surface of the spiral phase plate of the optical fiber integrated with the spiral phase plate through an optical fiber splitter, and the spiral phase plates on different optical fibers integrated with the spiral phase plate carry different topological charges to form a vortex random laser carrying different orbital angular momentum modes; the invention is applied to the random laser.

Description

Technical Field

[0001] The invention provides an optical fiber vortex random laser integrating multiple orbital angular momentum modes and a preparation method thereof, and a device and method for generating vortex random laser, belonging to the technical field of lasers. Background Art

[0002] With the rapid development of coherent optical theory, partially coherent vortex beams are considered to be a special type of vortex beams. Compared with fully coherent vortex beams, partially coherent vortex beams have some special physical meanings and optical properties. By adjusting its coherence and orbital angular momentum mode, physical effects such as disappearance of coherent singularities, beam shaping, beam self-repair and polarization state conversion will occur. It has unique advantages in suppressing speckle noise, breaking through the Rayleigh diffraction limit and resisting atmospheric turbulence disturbances. At present, partially coherent vortex beams are mainly passively generated by dynamic scatterer method, incoherent superposition method or pure digital holography. Among them, the dynamic scatterer method requires rotating frosted glass to passively generate low spatial coherence lasers, and the adjustment speed is limited. The other two methods have the advantages of flexible regulation, but require complex offline computational processing. Therefore, designing a light source with low spatial coherence is very necessary for generating partially coherent vortex beams in real time.

[0003] As a new type of partially coherent light source, random lasers have the characteristics of simple structure, flexible design, and low spatial coherence of radiated light. They have good application prospects in the fields of speckle-free imaging, biosensing, and information security. At present, researchers have used spatial light modulators to control the phase of random lasers, and have realized vortex random lasers covering the visible light and near-infrared bands, proving that random lasers can be used to actively generate partially coherent vortex beams in real time. However, these vortex random lasers still need to be strengthened in terms of radiation direction optimization and system integration. The method of controlling the phase based on spatial light modulators requires the use of multiple optical elements to collimate the beam, resulting in a complex optical path system, causing certain energy losses, which is not conducive to the integration and miniaturization of the system, and limits the practical application of vortex random lasers. In recent years, researchers have proposed that the optical confinement effect of optical fiber waveguides can effectively optimize the radiation direction of random lasers. At the same time, the end face of the optical fiber is a platform of the order of hundreds of microns that naturally has optical coupling conditions, which can be compatible with some mature planar micro-nano processing technologies. The method of generating vortex beams based on the microstructure of the fiber end face has the advantages of compact structure, easy integration, high robustness and long-distance transmission, that is, directly processing various micro-optical devices (spiral phase plate, fork grating or spiral axon) on the fiber end face to modulate the spatial phase of the incident light. Therefore, based on the waveguide effect and easy integration of optical fiber, modulating the phase of random lasers through specially designed fiber end face microstructures is conducive to the integrated design and radiation direction optimization of vortex random lasers. Summary of the invention

[0004] In order to solve the problems of existing vortex random lasers that the radiation direction needs to be optimized and the system integration needs to be strengthened, the present invention proposes an optical fiber vortex random laser integrating multiple orbital angular momentum modes and a preparation method thereof, as well as an apparatus and method for generating vortex random lasers. Based on the coupling of a random laser and an optical fiber, the phase of the random laser is modulated by etching a phase plate with different topological charges at the optical fiber end, and vortex random lasers with different orbital angular momentum modes are output from the optical fiber end.

[0005] The technical solution adopted by the present invention is: an optical fiber vortex random laser integrating multiple orbital angular momentum modes, comprising a microfluidic channel, a single-mode optical fiber, an optical fiber splitter and an optical fiber integrated with a spiral phase plate, wherein a gain medium and scattering particles are arranged in the microfluidic channel, one end of the single-mode optical fiber is solidified in the microfluidic channel, and the other end of the single-mode optical fiber is coupled with the end face where the spiral phase plate of the optical fiber integrated with the spiral phase plate is located through the optical fiber splitter, and the topological charges carried by the spiral phase plates on different optical fibers integrated with spiral phase plates are different, thereby forming a vortex random laser carrying different orbital angular momentum modes.

[0006] Furthermore, the gain medium is selected from laser dyes, quantum dots, perovskites or semiconductor materials, and by changing the type of gain medium, vortex random lasers can cover the visible light band range.

[0007] Furthermore, the scattering particles are selected from metal nanoparticles, metal nanowires or dielectric nanomaterials.

[0008] Furthermore, the spiral phase plate is etched using two-photon polymerization laser direct writing technology.

[0009] Further, the inner diameter of the microfluidic channel is 500±15 μm.

[0010] Furthermore, the cladding diameter of the single-mode optical fiber is 125±1.5 μm, the coating diameter is 245±15 μm, the numerical aperture is 0.13, and the operating wavelength is 600-770 nm.

[0011] A method for preparing a fiber vortex random laser integrating multiple orbital angular momentum modes comprises the following steps: Step 1: Mixing the gain medium and the scattering particles in a certain proportion in a polymethyl methacrylate solution to obtain a mixed solution; Step 2: Using the capillary action of the microfluidic channel, the mixed solution is sucked into the microfluidic channel; Step 3: Insert one end of the single-mode optical fiber into the microfluidic channel and then place it in a drying oven to complete the curing process to form a microfluidic random laser; Step 4: Using two-photon polymerization laser direct writing technology to etch spiral phase plates with different topological charges on the end face of the optical fiber, to obtain an optical fiber with an integrated spiral phase plate; Step 5: Use a fiber splitter to couple the other end of the single-mode fiber with the end face of the fiber with integrated spiral phase plate where the spiral phase plate is located, to form a fiber vortex random laser.

[0012] A device for generating a vortex random laser comprises a pump source, an optical fiber vortex random laser integrating a multi-orbital angular momentum mode, a half-wave plate, a Glan prism, a beam splitter, an optical power meter, a lens and an optical fiber spectrometer. The laser generated by the pump source is passed through the half-wave plate and the Glan prism to adjust the power and then forms two laser beams through the beam splitter. One of the laser beams is input into the optical power meter, and the other laser beam is input into the optical fiber spectrometer for measuring the radiation spectrum of the vortex random laser under different pump powers after passing through a first lens, the optical fiber vortex random laser and a second lens.

[0013] Furthermore, it also includes a computer, the optical power meter and the optical fiber spectrometer are connected to the computer through wires respectively, and the computer is also connected to a CCD camera for photographing the output light spots of vortex random lasers with different topological charges through wires.

[0014] A method for generating a vortex random laser, using a device for generating a vortex random laser, comprises the following steps: Step 6: The microfluidic random laser is excited by a pump source, and the random laser coupled into the single-mode optical fiber is split into multiple optical fibers integrated with spiral phase plates under the action of a fiber splitter; under the modulation of the spiral phase plate, vortex random lasers of different orbital angular momentum modes are output from the end face of the optical fiber integrated with the spiral phase plate; Step 7: Use the half-wave plate and Glan prism to adjust the power of the pump source, and use the optical power meter to monitor the pump power, and then repeat step 6; Step 8: Use a fiber spectrometer to measure the radiation spectrum of the vortex random laser at different pump powers.

[0015] The beneficial effects of the present invention compared with the prior art are as follows: (1) Based on the easy integration of optical fibers, the integration and miniaturization of vortex random lasers are achieved by etching spiral phase plates with different topological charges at the ends of optical fibers, and vortex random lasers with orbital angular momentum modes of 1-5 can be output simultaneously; (2) Based on the waveguide effect of optical fiber, the optimization of the vortex random laser radiation direction is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described below in conjunction with the accompanying drawings: Figure 1 is a device structure diagram of the present invention; Figure 2 It is a structural diagram of the optical path system of the present invention; Figure 3 This is an electron microscope image of the end face of an optical fiber etched with a spiral phase plate; Figure 4 The electron microscope images of spiral phase plates with different topological charges etched on the fiber end; Figure 5 It is the radiation spectrum diagram of the present invention at different pump power densities; Figure 6 The output spot diagram of vortex random laser with different orbital angular momentum modes; In the figure: 100 is a microfluidic channel, 101 is a gain medium, 102 is a scattering particle, 103 is a single-mode optical fiber, 104 is an optical fiber splitter, 105 is an optical fiber integrated with a spiral phase plate, 200 is a pump source, 201 is a half-wave plate, 202 is a Glan prism, 203 is a beam splitter, 204 is an optical power meter, 205 is a lens, 206 is a fiber vortex random laser, 207 is a fiber spectrometer, and 208 is a computer. DETAILED DESCRIPTION

[0017] like Figures 1 to 6 As shown, the present invention provides an optical fiber vortex random laser integrating multiple orbital angular momentum modes, comprising a microfluidic channel 100, a gain medium 101, scattering particles 102, a single-mode optical fiber 103, an optical fiber splitter 104, and an optical fiber 105 integrated with a spiral phase plate, wherein the gain medium 101 and the scattering particles 102 are mixed in a polymethyl methacrylate solution and solidified in the microfluidic channel 100 to form a microfluidic random laser; one end of the single-mode optical fiber 103 is also solidified in the microfluidic channel 100, and the other end is coupled with the optical fiber 105 integrated with a spiral phase plate under the action of the optical fiber splitter 104. Under the excitation of the pump source 200, the random laser radiated by the microfluidic random laser is coupled into the single-mode optical fiber 103 for transmission, and is respectively transmitted to the optical fiber 105 integrated with a spiral phase plate under the action of the optical fiber splitter 104; finally, under the phase modulation of the spiral phase plate, the optical fiber end outputs vortex random lasers of different orbital angular momentum modes.

[0018] When the specific gain medium 101 is excited by the pump source 200, the radiated light is multiply scattered by the randomly distributed scattering particles 102 to realize the light amplification process; at the same time, the total internal reflection at the interface between the microfluidic channel 100 and the air provides positive feedback for light amplification; when the total gain is greater than the loss, the radiation of random laser is realized; a part of the random laser is coupled into the single-mode optical fiber 103 for transmission, and is transmitted to multiple optical fibers 105 with integrated spiral phase plates under the action of the optical fiber splitter 104; finally, under the phase modulation of the spiral phase plate carrying different topological charges, the optical fiber end outputs vortex random lasers with different orbital angular momentum modes.

[0019] The gain medium 101 can be laser dye, quantum dot, perovskite or semiconductor material; by changing the type of gain medium 101, vortex random laser can cover the visible light band range.

[0020] The scattering particles 102 may be metal nanoparticles, metal nanowires, or dielectric nanomaterials.

[0021] The inner diameter of the microfluidic channel 100 is 500±15 μm.

[0022] The cladding diameter of the single-mode optical fiber 103 is 125±1.5 μm, the coating diameter is 245±15 μm, the numerical aperture is 0.13, and the operating wavelength is 600-770 nm.

[0023] The optical fiber splitter 104 is specifically a 1-to-5 splitter, which evenly splits the random laser in the single-mode optical fiber 103 into five paths according to energy.

[0024] The spiral phase plate integrated at the optical fiber end is prepared using two-photon polymerization laser direct writing technology, and the spiral phase plate carries topological charges of 1 to 5.

[0025] This embodiment also proposes a method for preparing a fiber vortex random laser integrating multiple orbital angular momentum modes, comprising the following steps: Step 1: mixing the gain medium 101 and the scattering particles 102 in a certain proportion in a polymethyl methacrylate solution to obtain a mixed solution; Step 2: Using the capillary action of the microfluidic channel 100 , the mixed solution is sucked into the microfluidic channel 100 ; Step 3: insert one end of the single-mode optical fiber 103 into the microfluidic channel 100, and then put it into a drying oven to complete the curing process to form a microfluidic random laser; Step 4: using two-photon polymerization laser direct writing technology to etch spiral phase plates with different topological charges on the end face of the single-mode optical fiber, to obtain an optical fiber 105 with an integrated spiral phase plate; Step 5: Use the fiber splitter 104 to couple the other end of the single-mode fiber 103 with the end face of the spiral stop plate of the fiber 105 with the integrated spiral phase plate to form a fiber vortex random laser, such as Figure 1 shown.

[0026] This embodiment also proposes a device for generating vortex random laser, including a pump source 200, an optical fiber vortex random laser 206 integrating multi-orbital angular momentum modes, a half-wave plate 201, a Glan prism 202, a beam splitter 203, an optical power meter 204, a lens 205, an optical fiber spectrometer 207 and a computer 208. After the power of the pump source 200 is regulated by the half-wave plate 201 and the Glan prism 202, the pump source 200 emits laser light through the beam splitter 203 to form two laser beams, one laser beam enters the optical power meter 204 as an auxiliary laser for detecting the pump power, and then the pump power measured by the optical power meter 204 is collected by the computer 208, and the other laser beam passes through the first lens, the optical fiber vortex random laser 206 and the second lens and enters the optical fiber spectrometer 207. The radiation spectrum of the vortex random laser 206 under different pump powers is measured by the optical fiber spectrometer 207, and the radiation spectrum is sent to the computer 208.

[0027] This embodiment also proposes a method for generating vortex random laser, based on the above-mentioned vortex random laser generating device, comprising the following steps: Step 6: The microfluidic random laser is excited by the pump source 200, and the random laser coupled into the single-mode optical fiber 103 is branched into multiple optical fibers 105 under the action of the optical fiber splitter 104; under the modulation of the spiral phase plate, vortex random lasers of different orbital angular momentum modes are output from the end face of the optical fiber 105; Step 7: Use the half-wave plate 201 and the Glan prism 202 to adjust the power of the pump source 200, and use the optical power meter 204 to monitor the pump power, such as Figure 2 As shown; Step 8: Using the fiber spectrometer 207 to measure the radiation spectrum of the vortex random laser at different pump powers; Step 9: Use CCD to capture the output spot of vortex random laser with different topological charges.

[0028] Embodiment 1: This embodiment provides a specific method for preparing a fiber vortex random laser integrating multiple orbital angular momentum modes and a method for generating a vortex random laser. The effectiveness of the present invention is verified by this embodiment. DCJTB dye is selected as a gain medium and Ti3C2 is selected as a scattering particle to generate a red vortex random laser, which includes the following steps: (1) dissolving 30 g of polymethyl methacrylate in an acetone solution to obtain a polymethyl methacrylate dilution solution; (2) Dissolving 1.5 mg of DCJTB dye and 0.2 mg of Ti3C2 in a polymethyl methacrylate diluent to obtain a mixed solution; and then using the capillary action of the microfluidic channel 100 to absorb the mixed solution into the microfluidic channel 100; (3) inserting one end of the single-mode optical fiber 103 into the microfluidic channel 100, and then placing it in a drying oven at 60°C to complete the curing process, thereby forming a microfluidic random laser; (4) Using two-photon polymerization laser direct writing technology to etch a spiral phase plate with a topological charge of 1-5 on the end face of a single-mode optical fiber, such as Figure 3-4 As shown; (5) Using a 1-to-5 optical fiber splitter 104, the other end of the single-mode optical fiber 103 is coupled to the five optical fibers of the integrated spiral phase plate to form a fiber vortex random laser; (6) using a nanosecond laser with a wavelength of 532 nm to pump the microfluidic random laser, and collecting the radiation spectrum at the end of the optical fiber through a fiber spectrometer 207; Figure 5 As shown in Figure 2, it can be seen that when the pump power density is greater than 0.0567 MW / cm 2 When , a red vortex random laser with a central wavelength of 660nm is generated; (7) Use CCD to capture the output spot of vortex random laser with different topological charges. Figure 6 The output spot diagrams of vortex random lasers with topological charges of 1-5 are given. It can be seen that as the topological charge increases, an area with an intensity of 0 appears in the center of the intensity distribution, similar to a "donut" shape, indicating the existence of a phase singularity; at the same time, the spot diameter gradually increases. The results show that the spiral phase plate at the end of the optical fiber has a good modulation of the phase of the random laser, and the present invention realizes the integration of vortex random lasers with different orbital angular momentum modes.

[0029] In summary, the present invention proposes for the first time an optical fiber vortex random laser integrating different orbital angular momentum modes. The vortex random laser effectively optimizes its radiation direction based on the waveguide effect of the optical fiber. At the same time, the easy integration of the optical fiber is used to realize the integration and miniaturization of the vortex random laser. Based on the easy integration of the optical fiber, vortex random lasers with topological charges of 1-5 can be output simultaneously, which has potential application prospects in the fields of speckle-free imaging, optical communication and particle manipulation.

[0030] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber vortex random laser integrating multiple orbital angular momentum modes, characterized in that: The invention comprises a microfluidic channel (100), a single-mode optical fiber (103), an optical fiber splitter (104), and an optical fiber (105) with an integrated spiral phase plate. A gain medium (101) and scattering particles (102) are arranged in the microfluidic channel (100). One end of the single-mode optical fiber (103) is solidified in the microfluidic channel (100). The other end of the single-mode optical fiber (103) is coupled to the end face of the spiral phase plate of the optical fiber (105) with an integrated spiral phase plate through the optical fiber splitter (104). The topological charges carried by the spiral phase plates on different optical fibers (105) with integrated spiral phase plates are different, thereby forming vortex random lasers carrying different orbital angular momentum modes.

2. The fiber vortex random laser integrating multiple orbital angular momentum modes according to claim 1, characterized in that: The gain medium (101) is selected from laser dyes, quantum dots, perovskites or semiconductor materials, and by changing the type of the gain medium (101), vortex random lasers can cover the visible light band range.

3. The fiber vortex random laser integrating multiple orbital angular momentum modes according to claim 1, characterized in that: The scattering particles (102) are selected from metal nanoparticles, metal nanowires or dielectric nanomaterials.

4. The fiber vortex random laser integrating multiple orbital angular momentum modes according to claim 1, characterized in that: The spiral phase plate was etched using two-photon polymerization laser direct writing technology.

5. The fiber vortex random laser integrating multiple orbital angular momentum modes according to claim 1, characterized in that: The inner diameter of the microfluidic channel (100) is 500±15 μm.

6. The fiber vortex random laser integrating multiple orbital angular momentum modes according to claim 1, characterized in that: The cladding diameter of the single-mode optical fiber (103) is 125±1.5 μm, the coating diameter is 245±15 μm, the numerical aperture is 0.13, and the operating wavelength is 600-770 nm.

7. A method for preparing a fiber vortex random laser integrating multiple orbital angular momentum modes as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: mixing a gain medium (101) and scattering particles (102) in a certain proportion in a polymethyl methacrylate solution to obtain a mixed solution; Step 2: utilizing the capillary action of the microfluidic channel (100) to draw the mixed solution into the microfluidic channel (100); Step 3: inserting one end of the single-mode optical fiber (103) into the microfluidic channel (100), and then placing it in a drying oven to complete the curing process, thereby forming a microfluidic random laser; Step 4: using two-photon polymerization laser direct writing technology to etch spiral phase plates with different topological charges on the end face of the optical fiber, to obtain an optical fiber (105) with an integrated spiral phase plate; Step 5: Using an optical fiber splitter (104), the other end of the single-mode optical fiber (103) is coupled to the end face of the optical fiber (105) with an integrated spiral phase plate where the spiral phase plate is located, thereby forming an optical fiber vortex random laser.

8. A device for generating vortex random lasers, characterized in that: The invention comprises a pump source (200), an optical fiber vortex random laser (206) with integrated multi-orbital angular momentum modes as claimed in any one of claims 1 to 6, a half-wave plate (201), a Glan prism (202), a beam splitter (203), an optical power meter (204), a lens (205) and an optical fiber spectrometer (207), wherein the laser light generated by the pump source (200) is passed through a half-wave plate (201) and a Glan prism (202) to adjust the power and then forms two laser beams through the beam splitter (203), wherein one laser beam is input into the optical power meter (204), and the other laser beam is input into the optical fiber spectrometer (207) for measuring the radiation spectrum of the vortex random laser under different pump powers after passing through a first lens, the optical fiber vortex random laser (206) and a second lens.

9. The device for generating a vortex random laser according to claim 8, characterized in that: The invention also includes a computer (208), wherein the optical power meter (204) and the optical fiber spectrometer (207) are respectively connected to the computer (208) via wires, and the computer (208) is also connected to a CCD camera for photographing the output light spots of vortex random lasers with different topological charges via wires.

10. A method for generating a vortex random laser, using the device for generating a vortex random laser as claimed in claim 8 or 9, characterized in that: The following steps are involved: Step 6: using a pump source (200) to excite a microfluidic random laser, the random laser coupled into the single-mode optical fiber (103) is split into a plurality of optical fibers (105) integrated with spiral phase plates under the action of an optical fiber splitter (104); under the modulation of the spiral phase plate, vortex random lasers of different orbital angular momentum modes are output from the end face of the optical fiber (105) integrated with the spiral phase plate; Step 7: using a half-wave plate (201) and a Glan prism (202) to adjust the power of the pump source (200), and using an optical power meter (204) to monitor the pump power, and then repeating step 6; Step 8: Use a fiber spectrometer (207) to measure the radiation spectrum of the vortex random laser at different pump powers.

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