Random laser for super-resolution spectrum reconstruction

Abstract

The invention discloses a random laser for super-resolution spectrum reconstruction, the laser comprises a nested fiber structure and a random gain medium, and an output spectrum has sparsity and ergodicity of a frequency domain. The random gain medium comprises a scattering material and a gain material, the optical fiber nested structure is formed by inserting an optical fiber into a hollow optical fiber, the structure is simple, integration is easy, and the preparation cost is low. The central optical fiber provides an optical waveguide and outputs directional radiation laser; the optical fiber outer wall and the hollow-core optical fiber inner wall provide strong feedback for random scattering, the Q factor of the cavity is improved, small peaks with discrete spectrums are output, the spectral purity is high, and the signal-to-noise ratio is high. The random laser is used as an illumination source of a low-resolution spectrometer, and super-resolution spectrum reconstruction can be realized through frequency domain sparse sampling.

Description

Technical Field

[0001] The present invention relates to a random laser for super-resolution spectral reconstruction, and the spectrum output in the visible light range has sparse spikes with dynamically random distribution and high signal-to-noise ratio, belonging to the field of optoelectronic technology. Background Art

[0002] In the field of optics, the spectrum is an important means to characterize substances. Spectral detection is limited by the resolution of the spectrometer and cannot break through the diffraction limit of the instrument, which restricts the improvement of spectral resolution. Some researchers have proposed that through sparse sampling in the frequency domain, super-resolution reconstruction of the sample spectrum can be achieved. The realization of this method requires the spectrum of the light source to have sparsity and ergodicity. A random laser uses multiple scattering of light in a disordered gain medium to achieve stimulated emission amplification, and emits light with a completely random output mode. Its output spectrum is composed of discrete small spikes with a line width less than 1 nm, and the emission spectra at different times are completely uncorrelated, indicating that its spectrum has sparsity; secondly, the output mode of the random laser has a wide distribution in frequency and can cover the spectral range of its gain, and the output spectrum has ergodicity. Using it as the light source of the spectrometer not only meets the requirements for the brightness of the light source but also enables super-resolution spectral reconstruction. Compared with traditional spectral detection methods, the super-resolution spectrometer has higher spectral resolution and stronger anti-interference ability, and can achieve accurate characterization of samples. However, in the visible light band, the current random lasers used in super-resolution spectrometers are large in volume, difficult to integrate, have low spectral signal-to-noise ratio, affect the accuracy of the reconstructed spectrum, have poor directivity, and cause serious energy loss. Summary of the Invention

[0003] The present invention provides a random laser for super-resolution spectral reconstruction, which can break through the diffraction limit of the spectrometer. The laser is integrated on an optical fiber and has the characteristics of directional output and integrability. Its output spectrum has high mode purity and large signal-to-noise ratio. The random laser includes a fiber nested structure, a scattering material, and a gain material. The fiber nested structure consists of a hollow fiber and an optical fiber. The scattering material and the gain material are mixed to form a disordered gain medium, and the disordered gain medium is filled into the voids of the fiber nested structure.

[0004] A method for manufacturing a random laser for super-resolution spectral reconstruction includes the following steps:

[0005] 1. Uniformly disperse the gain medium and scattering particles in a solvent and perform ultrasonic oscillation to prepare a disordered gain medium suspension. The scattering particles are dielectric particles or metal particles, such as titanium dioxide nanoparticles, gold nanoparticles, etc., which serve as the light scattering source and provide feedback for the formation of random laser. The gain material is a laser dye, a perovskite quantum dot, a rare earth material, etc., which provides gain for the formation of laser and realizes random laser.

[0006] 2. Insert the solid optical fiber with polished end faces into the hollow optical fiber. The inner diameter of the hollow optical fiber is slightly larger than the outer diameter of the solid optical fiber, forming a gap between the inner wall of the hollow optical fiber and the outer wall of the solid optical fiber. The solid optical fiber serves as the optical transmission medium to control the emission direction of the laser. The boundaries between the outer wall of the hollow optical fiber and the inner wall of the solid optical fiber as the disordered gain medium provide feedback enhancement for random scattering, improving the output spectral mode purity and signal-to-noise ratio. The width of the gap between the optical fibers is 5 - 50 μm.

[0007] 3. Inject the disordered gain medium solution prepared in step (1) into the gap between the hollow optical fiber and the solid optical fiber in the structure of step (2) using a syringe, and utilize the siphon effect to form a liquid core of the disordered gain medium in the gap ( Figure 1 ). The length of the liquid core is greater than 1 mm.

[0008] 4. Reconstruct the super-resolution spectrum: Use the realized random laser as the illumination source of the low-resolution spectrometer. The randomly emitted laser is divided into two beams. One beam is directly coupled into the low-resolution spectrometer (i.e., the reference light), and the other beam passes through the sample and then enters the low-resolution spectrometer (i.e., the signal light). The signal light and the reference light are simultaneously imaged on the camera (the optical path is as Figure 2 ), and 1000 - 5000 spot photos are collected. Calibrate the wavelength of the spectrometer with a standard light source ( Figure 3 ). After screening the peaks of each random laser flash and locating their central wavelengths ( Figure 4 ), divide the integrated intensity of the reference spot by the integrated intensity of the signal spot to obtain the transmittance of the sample at a certain wavelength. Perform this operation on all pairs of reference spots and transmitted spots to reconstruct the high-resolution spectrum of the sample ( Figure 5 ). The optical coupling method is spatial coupling or fiber coupling, and the camera is a CCD or CMOS camera.

[0009] Advantages and features of the present invention:

[0010] 1. The random laser in the present invention is assembled on the optical fiber and can be integrated on different devices, suitable for the development and application of micro-devices.

[0011] 2. Coupling the fiber waveguide with the random laser can control the emission direction of the random laser and achieve the directional output of random laser.

[0012] 3. By means of the fiber nested structure, the boundary of the random gain system is constructed, enhancing the optical feedback and realizing the spectral output with high purity and high signal-to-noise ratio.

[0013] 4. The random laser structure of the present invention is simple, the design is flexible, the preparation method has low cost and high preparation efficiency.

[0014] 5. The spectral output in any wavelength range can be achieved by changing the gain medium.

[0015] 6. Using it as the illumination source of a low-resolution spectrometer can achieve super-resolution spectral reconstruction. The resolution can be increased by a hundred times without using expensive equipment. Description of the Drawings

[0016] Figure 1 shows the structure of the random laser in the present invention;

[0017] Among them, 1.1 is the disordered gain medium solution, 1.2 is the optical fiber, and 1.3 is the hollow optical fiber; the left figure is the end face of the random laser, the right figure is the side cut surface of the random laser, and the middle is the three-dimensional view of the random laser.

[0018] Figure 2 shows the optical path diagram for super-resolution spectral reconstruction in the present invention;

[0019] Among them, 2.1: the excitation source of the random laser, 2.2: the random laser of the present invention, 2.4: the dichroic mirror, 2.5: the 50:50 beam splitter, 2.8: the sample to be measured, 2.19: the low-resolution spectrometer, 2.3, 2.9, 2.10, 2.11, 2.12, 2.18: lenses, 2.7, 2.14, 2.16: mirrors, 2.13: slit, 2.15: grating, 2.17: camera.

[0020] Figure 3 shows the schematic diagram of the calibration process of the low-resolution spectrometer.

[0021] Among them, 3.1 and 3.2 are two light spots obtained by the camera for the calibration light source, 3.3 and 3.4 are the spectra corresponding to the camera images of the calibration light source, and 3.5 is the camera "pixel-wavelength" lookup curve generated using the calibration light source.

[0022] Figure 4 shows the photo of a single flash of the reference light and the probe light of the random laser during the spectral detection process.

[0023] Among them, 4.1 is the reference light image collected by the camera of the low-resolution spectrometer, and 4.2 is the probe light image collected by the camera of the low-resolution spectrometer. Figure 4 includes the spectrum corresponding to the camera image of the super-resolution spectrometer, where the solid line 1 represents the spectrum of the reference light, the dashed line 2 represents the spectrum of the probe light, and the selected peaks are indicated by the gray areas. The three gray areas of 4.3, 4.4, and 4.5 represent the three peak positions selected for reconstruction in this flash, and the vertical solid lines in the gray areas represent the central wavelengths of these three peak positions.

[0024] Figure 5 shows the result of super-resolution spectral reconstruction in the present invention.

[0025] Among them, 5.1 and 5.2 are the reconstructed spectrum and the standard spectral curve of the sample, and 5.3 and 5.4 are the frequency spectrum curves of the reconstructed spectrum and the standard spectrum. Specific implementation mode

[0026] Example 1: A super-resolution spectrometer based on a random laser, comprising the following steps:

[0027] 1. Dissolve 3 mg of rhodamine B (RhB) dye in 100 μL of aqueous solution, disperse 0.075 mg of titanium dioxide nanoparticles (TiO 2 NPs) in the above solvent, and mix evenly. Then, add 1 mL of glycerol to the above mixed solution, stir at room temperature for 30 minutes until completely mixed evenly, and heat at 80 °C for 2 hours to completely evaporate the water solvent, obtaining a uniformly mixed disordered gain medium solution. The final concentration of RhB is 3 mg mL -1 , and the final concentration of TiO 2 NPs is 0.075 mg mL -1 .

[0028] 2. Cut the optical fiber into 5 cm in length. The cladding diameter of the optical fiber is 660 μm, and the core diameter is 600 μm. Polish its end face and immerse it in acetone solution for 30 minutes to remove the resin layer of the optical fiber. Place it in a beaker and ultrasonically clean it in acetone solution, ethanol solution, and deionized water for 5 minutes in sequence. Clean the silica hollow-core optical fiber in the above manner. The inner diameter of the hollow-core optical fiber is 680 μm, the outer diameter is 1.5 mm, the length is 3 cm, and the refractive index is 1.46.

[0029] 3. Insert the optical fiber into the silica hollow-core optical fiber to form a nested structure. Use a syringe to inject the disordered gain medium solution prepared in step (1) into the junction between the silica hollow-core optical fiber and the optical fiber, and use the siphon effect to form a layer of random laser liquid core in the gap between the hollow-core optical fiber and the optical fiber ( Figure 1 ).

[0030] 4. Use a wavelength-tunable laser as the light source to calibrate the spectrometer ( Figure 3 ). The output light of the random laser is divided into two paths by a 50:50 beam splitter ( Figure 2 ). Couple one path of the light beam into a low-resolution spectrometer through an optical fiber as the reference light, and at the same time, couple the other path of the light beam through the sample (FP filter) as the signal light into the low-resolution spectrometer through an optical fiber. After passing through the low-resolution spectrometer, the signal light and the reference light are simultaneously imaged on a CMOS camera. Perform sparse sampling in the frequency domain, record 5000 spot photos, including the peak amplitude and frequency of individual random laser pulses, and divide the integrated intensity of the reference spot by the integrated intensity of the signal spot to obtain the transmittance of the sample at a certain wavelength.Figure 4 ), performing this operation on all pairs of reference light spots and transmitted light spots enables the reconstruction of the spectrum of the FP cavity ( Figure 5 ). The reconstructed spectral details are exactly the same as those measured by a high-resolution spectrometer.

Claims

1. A random laser for super-resolution spectral reconstruction, characterized in that: The laser comprises a disordered gain medium solution (1.1), a solid optical fiber (1.2) and a hollow-core optical fiber (1.3); the disordered gain medium solution (1.1) is made by uniformly dispersing scattering particle materials and gain materials in a solution; the solid optical fiber (1.2) is inserted into the hollow-core optical fiber (1.3) to form a coaxial nested structure; and the disordered gain medium solution (1.1) is filled in the gap of the nested structure to form a tubular liquid core.

2. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The inner diameter of the hollow optical fiber (1.3) is larger than the outer diameter of the solid optical fiber, and a gap is formed between the inner wall of the hollow optical fiber (1.3) and the outer wall of the solid optical fiber (1.2); the width of the gap between the optical fibers (1.2) is 5-50 μm.

3. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The solid optical fiber (1.2) serves as an optical transmission medium to control the emission direction of the laser; the outer wall of the hollow optical fiber (1.3) and the inner wall of the solid optical fiber (1.2) serve as the boundary of the disordered gain medium to provide feedback enhancement for random scattering, thereby improving the output spectrum mode purity and signal-to-noise ratio.

4. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The hollow-core optical fiber (1.3) and the solid-core optical fiber (1.2) are borosilicate glass hollow-core optical fibers, plastic optical fibers or quartz glass hollow-core optical fibers.

5. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The scattering particles are dielectric particles or metal particles, such as titanium dioxide nanoparticles or gold nanoparticles, which serve as light scattering sources and provide feedback for the formation of random lasers. The gain materials are laser dyes, perovskite quantum dots, and rare earth materials, which provide gain for the formation of lasers and realize random lasers. The gain materials and scattering particles are adjusted according to the required working bands.

6. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The length of the tubular liquid core at the gap between the hollow-core optical fiber and the solid-core optical fiber is greater than 1 mm.

7. The random laser for super-resolution spectral reconstruction according to claim 1, characterized in that: The output spectrum of the random laser is discrete small peaks with a peak line width of less than 1 nm; the spacing between the peaks is much larger than the resolution limit of the spectrometer; the spectrum has no fluorescence envelope background and has a large signal-to-noise ratio.

8. A method for manufacturing a random laser for super-resolution spectrum reconstruction as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: Step (1) uniformly disperses the gain medium and scattering particles in a solvent, and ultrasonically oscillates to form a disordered gain medium suspension. The scattering particles are dielectric particles or metal particles, which serve as a scattering source of light and provide feedback for the formation of random lasers. The gain material is a laser dye, perovskite quantum dots, or a rare earth material, which provides gain for the formation of lasers and realizes random lasers. Step (2), inserting a solid optical fiber with a polished end face into a hollow-core optical fiber, wherein the inner diameter of the hollow-core optical fiber is larger than the outer diameter of the solid optical fiber, and a gap is formed between the inner wall of the hollow-core optical fiber and the outer wall of the solid optical fiber. The solid optical fiber is used as an optical transmission medium to control the emission direction of the laser. The outer wall of the hollow-core optical fiber and the inner wall of the solid optical fiber serve as the boundary of the disordered gain medium to provide feedback enhancement for random scattering, thereby improving the output spectral mode purity and signal-to-noise ratio. The width of the gap between the optical fibers is 5-50 μm. Step (3), injecting the disordered gain medium solution prepared in step (1) into the gap between the hollow-core fiber and the solid-core fiber in the structure of step (2) using a syringe, and forming a layer of disordered gain medium liquid core in the gap by using the siphon effect. The length of the liquid core is greater than 1 mm. Step (4), reconstructing the super-resolution spectrum: the random laser realized above is used as the illumination source of the low-resolution spectrometer, and the random laser output in a directional manner is divided into two beams, one beam of light is directly coupled into the low-resolution spectrometer, i.e., the reference light, and the other beam of light passes through the sample and enters the low-resolution spectrometer, i.e., the signal light. The signal light and the reference light are imaged on the camera at the same time, and 1000-5000 photos of the light spots are collected. The wavelength of the spectrometer is calibrated with a standard light source, and after screening and locating the central wavelength of each random laser flash peak, the integrated intensity of the reference light spot is divided by the integrated intensity of the signal light spot to obtain the transmittance of the sample at a certain wavelength. This operation is performed on all pairs of reference light spots and transmission light spots to reconstruct the high-resolution spectrum of the sample.

9. The method for manufacturing a random laser for super-resolution spectrum reconstruction according to claim 8, characterized in that: The optical coupling method is spatial coupling or fiber coupling.

10. The method for manufacturing a random laser for super-resolution spectrum reconstruction according to claim 8, characterized in that: The camera is a CCD or CMOS camera.

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