Intracavity light field modulation method based on Fabry-Perot microcavity internal device

Abstract

The invention belongs to the technical field of light field modulation, and particularly relates to a light field modulation method based on a Fabry-Perot microcavity internal device. The method comprises the following steps: based on a micro-nano light processing scheme, constructing a Fabry-Perot microcavity laser based on intracavity low-light element light field shaping, and then placing the laser in a light field test system; the method comprises the following steps: (1) detecting an output laser pattern, and controllably constraining and modulating an intracavity light field by adjusting the position of a laser; (2) detecting an output laser spectrum, further adjusting the pumping energy to obtain a relation between a spectrum peak value and the pumping energy, and realizing high-quality factor single-mode laser; by designing the matching relation between the optical continuous interface or diffraction structure configuration and the micro-cavity configuration in the micro-cavity laser, the performance parameters of the Fabry-Perot micro-cavity and the modulation of the intra-cavity light field can be realized, so that the high-quality factor micro-cavity laser and the customized output of the light field in a specific laser mode are realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical field modulation of optical cavity devices, and particularly relates to an optical field modulation method based on internal devices of a Fabry-Perot microcavity. Background Art

[0002] The spatial shaping of laser beams is a core topic in modern optical research. The unique properties of Fabry-Perot optical microcavities (such as sub-wavelength mode volume, ultra-high quality factor Q value) bring new challenges and opportunities for optical field regulation. Traditional microcavities mainly rely on external passive extra-cavity generation and regulation of optical fields. The extra-cavity beam shaping requires the introduction of discrete amplitude or phase elements, which not only leads to additional insertion losses and inherent stray light problems, but also increases the complexity of the optical path, restricting the integration and stability of optical elements at the micro-nano scale and making it difficult to achieve high-efficiency regulation. In order to break through the limitations of the separation of fixed resonators and external beam shaping, the optical field regulation mechanism of micro-nano optical microcavities has gradually evolved from passive cavities to active cavities, embedding the optical field regulation function into the eigenmodes of the resonator and reconstructing the interaction paradigm between photons and the resonator. By directly integrating tunable materials or dynamic microstructures at the micro-nano scale, the target optical field can be directly and real-timely reconstructed during the resonance process, forming an integrated design of cavity-as-a-system. This cavity mode tailoring strategy not only avoids the efficiency loss caused by external shaping, but also realizes dynamic regulation with sub-wavelength accuracy through the strong local field interaction between the cavity mode and the regulation element.

[0003] Currently, there are various active Fabry-Perot microcavity construction strategies: one is the intra-cavity integration type, which introduces focusing elements such as microspheres and microbubbles in the cavity to achieve mode field confinement, but there are significant defects in its dynamic stability and process repeatability, and the structural designability and freedom are limited; the second is the plano-concave configuration microcavity, which constructs curved cavity mirrors by means of processes such as focused ion beam milling and laser ablation combined with thin film deposition technology. Although high Q values and ultra-small mode volumes can be achieved, precise curved surface processing depends on high-cost equipment and it is difficult to customize complex curved surfaces; the third is the field engineering strategy of cavity surface microstructure regulation, which constructs sub-wavelength structures such as metasurfaces or BICs to regulate parameters such as optical field topological charge and polarization state. It also requires expensive and complex processes, and there is generally a contradiction between high freedom and low Q value. Therefore, it is meaningful to develop the customization of device configuration-device physical models to achieve precise coordinated regulation of the optical characteristics and functional design of Fabry-Perot microcavities. Summary of the Invention

[0004] The purpose of the present invention is to provide an optical field modulation method based on internal devices of a Fabry-Perot microcavity with high precision and low cost.

[0005] The optical field modulation method based on internal devices of a Fabry-Perot microcavity provided by the present invention includes the following steps:

[0006] (1) Build a Fabry - Perot micro - cavity laser based on intracavity micro - optical element shaping. Its structure includes: two planar mirrors, namely the first planar mirror and the second planar mirror, a spacer, and a laser gain medium. Among them, high - reflectivity thin films are coated on the surfaces of the first planar mirror and the second planar mirror, and a micro - optical element is fabricated on the surface of the second planar mirror. The first planar mirror and the second planar mirror are placed parallel to each other. The spacers have the same diameter and are located at the four corners of the two planar mirrors to separate the two planar mirrors. The surface of the second mirror with the micro - optical element (i.e., micro - nano device) faces the inside of the micro - cavity, and the laser gain medium is sandwiched in the center of the two planar mirrors. After applying a certain pressure to keep the two planar mirrors highly parallel, the two planar mirrors are bonded and fixed to form a Fabry - Perot - structured laser resonator integrated with micro - optical elements.

[0007] (2) Place the Fabry - Perot micro - cavity laser in an optical field test system, monitor the output laser pattern, adjust the position of the laser resonator, move the intracavity micro - optical element towards the center of the laser beam or create a certain displacement between it and the center of the pump beam until the detection system detects the output lasing spot. The generated lasing spot has a smaller mode volume and a special spot pattern compared to the traditional planar micro - cavity without intracavity devices, and the optical field is controllably confined and modulated inside the cavity.

[0008] (3) Place the Fabry - Perot micro - cavity laser in an optical field test system, monitor the output laser spectrum, adjust the position of the laser resonator, move the intracavity micro - optical element towards the center of the laser beam or create a certain displacement between it and the center of the pump beam until the detection system detects the output lasing spectrum. A spectrum after mode selection can be obtained, especially the selection of single - mode laser. Further adjusting the pump energy can obtain the relationship between the spectral integral and the pump energy, that is, the lasing threshold curve of the micro - cavity, and a very low - mode laser threshold can be obtained.

[0009] The optical field test system is a conventional optical field test system, as shown in Figure 2 shown.

[0010] Furthermore:

[0011] The planar mirror uses quartz glass as the substrate and is coated with a high - reflectivity dielectric film with a reflectivity greater than 99.5%.

[0012] The spacer is a polystyrene microsphere.

[0013] The laser gain medium is a liquid dye soluble in water or organic solvents (such as green fluorescent dyes like sodium fluorescein, FITC, etc., and red fluorescent dye R6G, etc.).

[0014] The intracavity micro-optical element mentioned above is a refractive free-form surface element, a diffractive element, or a hybrid refractive / diffractive element based on a transparent dielectric material. Further, the continuous free-form surface element mainly includes a spherical microlens and an axicon (see Figure 1 (a), (d)), the diffractive element is a phase zone plate (see Figure 1 (b)), and the hybrid refractive / diffractive element is a harmonic diffractive lens (see Figure 1 (c)). The spherical microlens is a plano-convex lens that focuses light through refraction; the phase zone plate consists of alternating concentric rings, and both odd and even rings remain optically transparent. This periodic diffraction structure can adjust the phase of the incident light, enabling different diffraction orders to interfere coherently on the focal plane to form a high-intensity focus; the harmonic diffractive lens combines the advantages of a refractive lens and a diffractive lens. While maintaining the thinness characteristics of the diffractive lens and the high energy concentration efficiency of the refractive lens, it can also overcome the chromatic dispersion change of the focal length at discrete wavelengths; the axicon can convert a plane wave into an approximately non-diffracting Bessel beam, generating a section of non-diffracting maximum collimation distance. The spherical microlens, phase zone plate, and harmonic diffractive lens are focusing elements. Different focal lengths correspond to different light field confinement effects and can be applied to controllably confine the light field inside the cavity, localize the light field, and thus enhance the interaction between light and matter; the axicon is a shaping micro-optical element used to shape the intracavity light field into structured light with a Bessel-Gaussian mode; the spherical microlens is used to achieve the output of high-order laser modes of different orders by controlling the relative position between the center of the microlens and the center of the pump beam.

[0015] The preparation of the Fabry-Perot microcavity surface micro-nano device can be achieved based on various micro-nano manufacturing technology platforms, such as, but not limited to, ultraviolet or gray-scale lithography and semiconductor processes, laser direct writing, and micro-nano imprinting;

[0016] The specific steps of the laser direct writing technology are as follows:

[0017] S1: Cleaning: Clean the plane mirror and dry it.

[0018] S2: Spin coating: Spin coat a layer of photoresist on the surface of the plane mirror and dry it.

[0019] S3: Laser direct writing: Print the designed three-dimensional structure of the device on the surface of the plane mirror through laser direct writing technology.

[0020] S4: Post-baking: Further crosslink and cure the photoresist in the exposed area.

[0021] S5: Development: Place the plane mirror in a special developer for development to remove the uncrosslinked photoresist.

[0022] S6: Drying: Use nitrogen to blow off the developing solution on the surface, completing the device processing on the surface of the endoscope.

[0023] The configurations (such as plano-convex surface type, relief surface type) and parameters (such as focal length) of the intracavity devices can be quantitatively customized through micro-nano manufacturing technology;

[0024] The customized intracavity devices can further achieve quantitative customization of the intracavity optical field.

[0025] The present invention also provides an optical field test system based on the above Fabry-Perot microcavity type laser, as shown in the appendix Figure 2 It includes: pump laser 7, neutral density filter 8, beam splitter 9, beam splitter 10, focusing objective lens 11, Fabry-Perot microcavity type laser (also called integrated microcavity device) 12, sample stage 13, imaging lens 14, long-pass filter 15, CMOS camera 16, focusing lens 17, long-pass filter 18, spectrometer 19, optical energy meter 20, where the imaging lens 14, long-pass filter 15, and CMOS camera 16 form an imaging optical path, and the focusing lens 17, long-pass filter 18, and spectrometer 19 form a spectral detection optical path.

[0026] Among them, the pump laser 7 emits pump light, which passes through the neutral density filter 8 and is split into two beams of light by the beam splitter 9. One beam is incident on the optical energy meter 20, and the other beam is incident on the beam splitter 10 and the focusing objective lens 11 and then coupled into the integrated microcavity device 12. After aligning the integrated microcavity device 12 and the pump light through the sample stage 13, the integrated microcavity device 12 generates lasing. The lasing light is reflected back along the original path, received again by the focusing objective lens 11, and then split into two paths by the beam splitter 10. One path images the lasing optical field image information on the CMOS camera 16 after passing through the imaging lens 14 and the long-pass filter, and the other beam of light directly passes through the beam splitter 9 and is incident on the spectral detection optical path, and enters the spectrometer 19 after passing through the focusing lens 17 and the long-pass filter 18 in sequence. The spectrometer 19 receives the lasing spectral signal.

[0027] The described pump laser is used to emit pump light;

[0028] The described neutral density filter is used to regulate the energy magnitude of the emitted pump light;

[0029] The described focusing objective lens is used to couple the pump light source into the integrated microcavity device, and at the same time collect the output optical signal of lasing for imaging and spectral detection;

[0030] The described focusing objective lens is used to couple the lasing signal light into the spectrometer;

[0031] The described spectrometer is used to collect the emitted spectral signal;

[0032] The imaging lens and imaging objective lens are used to efficiently transfer the light field image to the CMOS camera;

[0033] The long-pass filter is used to block the short-wavelength pump light from passing through and select the long-wavelength lasing light to pass through;

[0034] The CMOS camera is used to image the light field image and the entire microcavity integrated device;

[0035] The sample stage is used to fix, position, and move the integrated microcavity sample;

[0036] The optical energy meter is used to detect the energy of the pump laser.

[0037] The technical principle and effect of the present invention are as follows:

[0038] The micro-laser based on the Fabry-Perot microcavity mainly consists of three elements: a laser cavity, a gain medium, and a pump source. When light is incident on the microcavity, due to the multiple reflections and interference of the mirrors, only light of a specific wavelength can form a stable standing wave mode in the cavity, that is, the resonant mode. The field distribution of the traditional Fabry-Perot cavity is determined by the cavity length and the mirror curvature, while the micro-optical elements of the present invention are directly integrated on the surface of the cavity mirror, and the light field distribution in the cavity is changed by local refractive index modulation (such as a micro-lens) or phase modulation (such as a phase zone plate). By designing the matching relationship between the micro-nano optical continuous interface or diffraction structure configuration and the microcavity configuration in the microcavity-type laser, the modulation of the light field in the cavity can be realized, thereby realizing a high-quality factor microcavity laser and the customized output of the light field of a specific laser mode. Description of the Drawings

[0039] Figure 1 It is a structural diagram of a Fabry-Perot microcavity-type laser based on intracavity element integration and optical micrographs of different intracavity devices. (a) to (d) respectively represent four different intracavity device integrated Fabry-Perot microcavities.

[0040] Figure 2 It is a light field and spectrum detection system of a Fabry-Perot harmonic laser with intracavity element integration.

[0041] Figure 3 It is the optical performance characterization of a Fabry-Perot microcavity integrated with a refractive spherical lens in the cavity. Among them, (a) to (c) respectively represent the lasing spectra at different cavity lengths, the inserted ones are the corresponding lasing light field images, the white dotted line is the processed structure contour, and (d) is the relationship between the spectral integration and the pump energy at different cavity lengths.

[0042] Figure 4Characterization of the optical properties of a Fabry - Perot microcavity integrated with an intra - cavity phase zone plate. Among them, (a) to (c) represent the lasing spectra at different cavity lengths respectively. The inserted images are the corresponding lasing light field images. The white dotted line is the processed structure contour, and (d) is the relationship between the spectral integration and the pump energy at different cavity lengths.

[0043] Figure 5 Characterization of the optical properties of a Fabry - Perot microcavity integrated with a harmonic diffraction lens. Among them, (a) to (c) represent the lasing spectra at different cavity lengths respectively. The inserted images are the corresponding lasing light field images. The white dotted line is the processed structure contour, and (d) is the relationship between the spectral integration and the pump energy at different cavity lengths.

[0044] Figure 6 Characterization of the optical properties of a Fabry - Perot microcavity integrated with an axicon. Among them, (a) is the lasing spectrum with a cavity length of 50μm, (b) is the corresponding lasing light field image, and (c) is the relationship between its spectral integration and the pump energy.

[0045] Figure 7 Images of the lasing light field of a Fabry - Perot microcavity integrated with a refractive spherical lens at different off - axis amounts of the spherical lens relative to the center of the pump beam inside the cavity.

[0046] Figure 8 Preparation method flow of intra - cavity components.

[0047] Reference numerals in the figure: 1 is a plane mirror; 2 is a gain medium; 3 is a refractive spherical lens; 4 is a phase zone plate; 5 is a harmonic diffraction lens; 6 is an axicon; 7 is a pump laser; 8 is a neutral density filter; 9 is a beam splitter; 10 is a beam splitter; 11 is a focusing objective; 12 is an integrated microcavity device; 13 is a sample stage; 14 is an imaging objective; 15 is a long - pass filter; 16 is a CMOS camera; 17 is a focusing lens; 18 is a long - pass filter; 19 is a spectrometer; 20 is an optical energy meter; 21 is SU - 8; 22 is a processing objective; 23 is a femtosecond focused beam; 24 is a cover glass; 25 is a structure for importing the processing program; 26 is a developer. Detailed implementation manners

[0048] The present invention will be further introduced below through embodiments in combination with the accompanying drawings.

[0049] Embodiment 1: A method for modulating the intra - cavity light field based on intra - cavity devices, including the following steps:

[0050] (1) A Fabry - Perot microcavity - type laser based on intracavity micro - optical element shaping is constructed. Its structure includes: two high - reflectivity plane mirrors, namely the first plane mirror and the second plane mirror, polystyrene microspheres, and gain dyes. The first plane mirror and the second plane mirror are placed in parallel. The polystyrene microspheres have the same diameter and are dispersed at the four corners of the two plane mirrors as spacers. The device processed on the surface of the second mirror is located inside the microcavity. The gain medium is sandwiched in the center of the two plane mirrors. After applying a certain pressure to keep the two plane mirrors highly parallel, the two plane mirrors are bonded and fixed to form a dye laser resonator with an integrated micro - optical element Fabry - Perot structure.

[0051] The first plane mirror and the second plane mirror are based on quartz glass and are coated with a high - reflectivity dielectric film with a reflectivity as high as 99.7%. The reflection band of the plane mirror is 500nm - 600nm, and the transmission band is 440nm - 480nm (transmittance > 90%).

[0052] The laser gain medium is a sodium fluorescein aqueous dye with a concentration of 5mM.

[0053] The diameters of the polystyrene microspheres are selected as 30, 50, and 80μm. Therefore, three types of integrated Fabry - Perot microcavities with cavity lengths of 30, 50, and 80μm can be fabricated.

[0054] The intracavity micro - optical element is a refractive spherical lens based on SU - 8 polymer with a designed focal length of 50μm and a thickness of 5μm.

[0055] (2) The output laser pattern is monitored through the optical field test system of the integrated Fabry - Perot microcavity - type laser. The position of the integrated microcavity device is adjusted. When the refractive spherical lens is moved towards the center of the laser beam and the cavity length is set at 30μm, the system detects a lasing spot with an extremely small mode volume (diameter ∼ 2μm), as shown in Figure 3 -a,b. The generated lasing spot has a smaller mode volume and fundamental - mode output characteristics compared to the traditional planar microcavity without intracavity devices. When the cavity length is set at 50μm, a lasing spot with a diverging and increasing mode volume but still having fundamental - mode characteristics is detected (diameter ∼ 5μm). When the cavity length is set at 80μm, lasing cannot be generated at a lower pump - energy level.

[0056] (3) Monitor the output laser spectrum through the optical field test system of the integrated Fabry - Perot micro - cavity laser. Adjust the position of the integrated micro - cavity device, move the refractive spherical lens towards the center of the laser beam. At cavity lengths of 30, 50, and 80 microns respectively, the system detects the output spectrum. Then adjust the pump energy, record the spectra at different pump energies, and obtain the relationship curve between the spectral integration and the pump energy at different cavity lengths, as shown in Figure 3 -d. When the cavity length is less than or equal to the designed focal length, the refractive spherical mirror integrated micro - cavity has an extremely low lasing threshold and can generate single - mode lasing, as shown in Figure 3 -b.

[0057] Furthermore, for the optical field test system of the integrated Fabry - Perot micro - cavity laser, the pump laser 7 emits pump light. After passing through the beam splitters 9, 10 and the focusing lens 11, it is coupled into the integrated micro - cavity device 12. The light lasing from the integrated micro - cavity device 12 is reflected back and is split into two paths by the beam splitter 9. One path injects the image information of the lasing optical field into the imaging optical path, and the other path serves as a signal and is incident on the spectral detection optical path. In the experimental system, the pump laser is a 473 - nm nanosecond laser, the focusing lens is 20 - fold magnification, the spectrometer is a fiber - optic spectrometer, and the cut - off wavelength of the long - wave pass filter is 500 nm.

[0058] For the analysis of the optical properties of the plano - convex spherical lens, based on the principles of geometric optics, the mathematical expression of its focal length can be expressed as:

[0059]

[0060] where \(n_2\) represents the refractive index of the ambient medium, \(R\) represents the curvature radius of the convex surface of the lens, and \(n\) L refers to the refractive index of the lens material. From the stability analysis of the resonator in geometric optics, it can be known that when \(0\leq L\leq f\), the micro - lens integrated Fabry - Perot micro - cavity can achieve stable resonance, that is, \(f\) determines the cavity length that can achieve stable and light - field confinement. Derived from the four - level equation, the quality factor of the integrated empty cavity without gain is about \(1.5\times10\) 5 (cavity length is 30 μm).

[0061] Example 2: Based on the parameters of Example 1, only change the following condition: The intra - cavity micro - optical element is a phase zone plate based on SU - 8 polymer with a designed focal length of 50 μm. The results of its lasing optical performance are shown in Figure 4 . Stable lasing is achieved when the cavity length is less than the focal length, equal to the focal length, and greater than the focal length. The light field is confined in the central annulus region of the phase zone plate, and the lasing spectrum generally remains in single - mode output. The extremely low threshold condition corresponds to an extremely high Q value.

[0062] For the analysis of the optical properties of the phase zone plate, the mathematical expression of its focal length can be expressed as:

[0063]

[0064] The mathematical expression for the thickness of the phase zone plate is as follows:

[0065] d = λ / [N(n L - n2)]

[0066] In this design, N = 3.

[0067] The multi - level diffraction and long focal depth of the phase zone plate increase its overlap with the gain medium and the fundamental mode, making its ability to stabilize the micro - cavity optical field more stable. Derived from the four - level equation, the integrated cavity quality factor without gain is approximately 7.2×10 4 (The cavity length is 30 μm).

[0068] Example 3: Based on the parameters of Example 1, only change the following conditions: The intra - cavity micro - optical element is a harmonic diffraction lens based on SU - 8 polymer with a designed focal length of 50 μm. The results of its lasing optical performance are shown in Figure 5 . Stable lasing is achieved when the cavity length is less than the focal length, equal to the focal length, and greater than the focal length, and the optical field is confined in the central region.

[0069] The harmonic diffraction lens is between a refractive lens and a diffraction lens, and its structure is obtained by subtracting a multi - level step from the aspherical lens profile with a designed focal length of 50 μm. Derived from the four - level equation, the integrated cavity quality factor without gain is approximately 2.4×10 5 (The cavity length is 30 μm).

[0070] Example 4: Based on the parameters of Example 1, only change the following conditions: The intra - cavity micro - optical element is an axicon based on SU - 8 polymer, and its structure is 20 μm in diameter and 6 μm in height. The results of its lasing optical performance are shown in Figure 6 . Placing the axicon close to the center of the light spot realizes the laser output of the Bessel - Gaussian mode ( Figure 6 a, b), and at the same time realizes an ultra - low pump - up threshold of ∼2 μJ / mm 2 ( Figure 6 c).

[0071] The maximum collimation distance of the axicon is:

[0072]

[0073] where a is the radius, n1 is the refractive index of the lens, n2 is the refractive index of the environment, and α is the bottom - angle of the axicon. When the maximum collimation distance is greater than the cavity length, the integrated micro - cavity can achieve stable lasing and the optical - field modulation of the Bessel - Gaussian beam in the cavity. Derived from the four - level equation, the integrated cavity quality factor without gain is approximately 2.3×104 。

[0074] Example 5: Based on the parameters of Example 1, only the following conditions are changed: the intra-cavity micro-optical element is a refractive spherical lens with a designed focal length of 100 μm based on SU-8 polymer, and the lasing optical performance results are shown in Figure 7 。To demonstrate the ability of this method to control high-order Gaussian modes, only a few classical laser output modes are selected here. By controlling the off-axis displacement, that is, the position of the element center relative to the pump beam center, when the displacement Δx = -1.21 μm and Δy = 0.15 μm, HG 1,0 mode will be obtained; when the displacement Δx = 0.87 μm and Δy = -1.24 μm, HG 0,1 mode will be obtained; when the displacement Δx = -7.74 μm and Δy = 0.62 μm, HG 19,0 mode will be obtained; when the displacement Δx = 0.21 μm and Δy = 6.94 μm, HG 0,12 mode will be obtained; when the displacement Δx = 2.85 μm and Δy = -2.12 μm, HG 4,2 mode will be obtained; when the displacement Δx = 4.49 μm and Δy = -2.65 μm, HG 9,4 mode will be obtained; the highest order of 19 is achieved. For the spherical lens, the larger its size, the higher the order that can be achieved. By controlling off-axis pumping, the overlap rate of pumping and different mode distributions can be changed to generate the desired high-order modes.

[0075] Example 6: The preparation process of the cavity surface structure of the integrated Fabry-Perot microcavity provided in Example 2 of the present invention is as Figure 7 , including the following steps:

[0076] S1: Cleaning: Take a plane mirror and ultrasonically clean it with acetone, isopropanol, and deionized water for 10 minutes each in sequence;

[0077] S2: Spin coating: Drop a drop of SU-8 photoresist in the center of the surface of the plane mirror in S1, spin coat it at 500 rpm for 10 seconds to make the glue evenly distributed, and then spin coat it at 1500 rpm for 30 seconds to form a film with a thickness of about 80 microns. Place the coated mirror on a hot plate, bake it at 65 °C for 5 minutes, and then bake it at 95 °C for 20 minutes to preliminarily cure the glue layer and remove the solvent;

[0078] S3: Laser direct writing: Import the designed device structure STL file into the program, and use a femtosecond laser direct writing device (wavelength 780 nm, pulse width 100 fs) to process the micro-structure on the surface of the plane mirror in S2. The processing objective lens is 100 times, set the laser power to 3 mW, and the scanning speed to 60 mm / s;

[0079] S4: Post-baking: Place the planar mirror from S3 on a hot plate and bake it at 95 °C for 10 minutes to promote the photochemical reaction and crosslinking;

[0080] S5: Development: Immerse the planar mirror from S4 in the SU-8 developer solution, let it stand for 2 minutes to remove the photoresist in the unexposed area, and then wash it with isopropyl alcohol;

[0081] S6: Drying: Use nitrogen to blow off the developer solution on the surface to complete the device processing on the surface of the cavity mirror.

[0082] In summary, the present invention provides a method for modulating the optical field of internal devices of a Fabry-Perot microcavity, which realizes the precise coordinated control of the optical characteristics and functional design of the Fabry-Perot microcavity through a micro-nano precision processing scheme with high precision and low cost characteristics.

[0083] The method of the present invention has certain guiding significance for applications such as optical micro-nano sensing and single-photon sources. Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. The described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Any embodiment that covers the scope of the claims of the present invention belongs to the scope of the present invention.

Claims

1. A light field modulation method based on an internal device of a Fabry-Perot microcavity, characterized in that: The specific steps are: (1) A Fabry-Perot microcavity laser based on intracavity micro-optical element shaping is constructed, wherein the structure includes: two plane mirrors, a spacer, and a laser gain medium; wherein the surfaces of the two plane mirrors are coated with a high reflectivity film, and a micro-optical element is prepared on the surface of one of the plane mirrors; the two plane mirrors are placed in parallel, the spacer has the same diameter and is located at the four corners of the two plane mirrors to separate the two plane mirrors, and the surface processed with the micro-optical element faces the microcavity; the laser gain medium is sandwiched in the center of the two plane mirrors; the two plane mirrors are bonded and fixed by applying a certain pressure to keep the two plane mirrors highly parallel to each other, thereby forming a Fabry-Perot structure laser resonant cavity with integrated micro-optical element; (2) placing the Fabry-Perot microcavity laser in a light field test system, monitoring the output laser pattern, adjusting the position of the laser resonant cavity, moving the intracavity micro-optical element toward the center of the laser beam or causing a certain displacement with the center of the pump beam, until the detection system detects the output laser spot, the generated laser spot has a smaller mode volume and a special spot mode than the traditional planar microcavity without intracavity devices, and the light field is controllably confined and modulated in the cavity; (3) The Fabry-Perot microcavity laser is placed in a light field test system, the output laser spectrum is monitored, the position of the laser resonant cavity is adjusted, and the micro-optical element in the cavity is moved toward the center of the laser beam or a certain displacement is generated between the microcavity and the center of the pump beam until the detection system detects the output lasing spectrum. The relationship between the spectral integral and the pumping energy can be obtained by further adjusting the pumping energy, that is, the lasing threshold curve of the microcavity.

2. The light field modulation method according to claim 1, characterized in that: The plane reflector is based on quartz glass and coated with a high-reflectivity dielectric film on the surface, with a reflectivity greater than 99.5%; The spacer is polystyrene microspheres; The laser gain medium is a liquid dye soluble in water or an organic solvent.

3. The light field modulation method according to claim 2, characterized in that: The intracavity micro-optical element is a refractive free-form surface element or a diffractive element or a refractive / diffractive hybrid element based on a transparent medium material. Specifically, the continuous free-form surface element is a spherical microlens and an axicon, the diffractive element is a phase zone plate, and the refractive / diffractive hybrid element is a harmonic diffraction lens; the spherical microlens is a plano-convex lens that focuses light by refraction; the phase zone plate is composed of alternating concentric rings, and both odd-numbered rings and even-numbered rings remain optically transparent. This periodic diffraction structure can adjust the phase of the incident light, so that different diffraction orders coherently interfere on the focal plane to form a high-intensity focus; The harmonic diffraction lens combines the advantages of the refractive lens and the diffractive lens, and while maintaining the thinness characteristics of the diffractive lens and the high energy concentration efficiency of the refractive lens, it can also overcome the dispersion variation of the focal length under discrete wavelengths; the axicon lens converts the plane wave into a nearly non-diffraction Bessel beam, generating a non-diffraction maximum collimation distance.

4. The light field modulation method according to claim 3, characterized in that: The micro-optical element is manufactured by laser nano direct writing technology, and the specific steps are as follows: S1: Cleaning: clean and dry the plane reflector; S2: Spin coating: Spin a layer of photoresist on the surface of the plane reflector and dry it; S3: Laser direct writing: The designed device 3D structure is printed on the surface of the plane reflector by laser direct writing technology; S4: Post-baking: to further cross-link and solidify the photoresist in the exposed area; S5： Development: Place the plane mirror in a special developer to remove the uncross-linked photoresist; S6: Blow dry: Use nitrogen to blow away the developer on the surface and complete the device processing on the cavity mirror surface; The use of laser nano-direct writing technology can achieve quantitative customization of the configuration and parameters of intracavity micro-optical components, thereby further achieving quantitative customization of the intracavity light field.

5. A light field testing system for a Fabry-Perot microcavity laser constructed in the method according to any one of claims 1 to 4, characterized in that: include: A pump laser (7), a neutral density filter (8), a first beam splitter (9), a second beam splitter (10), a focusing objective lens (11), a Fabry-Perot microcavity laser also known as an integrated microcavity device (12), a sample stage (13), an imaging lens (14), a first long-wave pass filter (15), a CMOS camera (16), a focusing lens (17), a second long-wave pass filter (18), a spectrometer (19), and a light energy meter (20); wherein the imaging lens (14), the first long-wave pass filter (15), and the CMOS camera (16) constitute an imaging optical path, and the focusing lens (17), the second long-wave pass filter (18), and the spectrometer (19) constitute a spectral detection optical path; wherein: A pump laser (7) emits pump light, which passes through a neutral density filter (8) and is then split into two beams by a first beam splitter (9). One beam is incident on a light energy meter (20), and the other beam is incident on a second beam splitter (10) and a focusing lens (11) and then coupled into an integrated microcavity device (12). After the integrated microcavity device (12) and the pump light are aligned by a sample stage (13), the integrated microcavity device (12) generates laser light, which is then reflected back along the original path and is refocused. The laser light is received by the focusing lens (11) and then divided into two paths through the second beam splitter (10). One path passes through the imaging lens (14) and the first long-wave pass filter (15) to form an image on the CMOS camera (16), and the other path directly passes through the first beam splitter (9) and enters the spectrum detection light path, passes through the focusing lens (17) and the second long-wave pass filter (18) in sequence, and then enters the spectrometer (19). The spectrometer (19) receives the laser spectrum signal.

6. The light field testing system according to claim 5, characterized in that: The pump laser is used to emit pump light; The neutral density filter is used to control the energy of the emitted pump light; The focusing objective lens is used to couple the pump light source into the integrated microcavity device and collect the output light signal of the lasing for imaging and spectral detection; The focusing objective lens is used to couple the laser signal light into the spectrometer; The spectrometer is used to collect the emitted spectral signals; The imaging lens and imaging objective lens are used to efficiently transmit the light field image to the CMOS camera; The long-wave pass filter is used to prevent the short-wavelength pump light from passing through and select the long-wavelength laser light to pass through; The CMOS camera is used to image the light field image and the entire microcavity integrated device; The sample stage is used to fix, position and move the integrated microcavity sample; The optical energy meter is used to detect the energy of the pump laser.

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