Bicyclic orthogonally-rotating symmetric polarization frequency-doubled hollow laser

Abstract

The application discloses a double-ring orthogonal rotation symmetry polarization frequency doubling hollow laser, and the conical surface of a negative uniaxial crystal cone and the conical surface of a third negative cone mirror constitute a tangential polarization fundamental frequency (or radial polarization frequency doubling) hollow laser resonant cavity; the conical surface of a positive uniaxial crystal cone and the conical surface of the third negative cone mirror constitute a radial polarization fundamental frequency (or tangential polarization frequency doubling) hollow laser resonant cavity; the third plane mirror is an output coupling mirror of the frequency doubling hollow laser; the laser gain medium is circularly pumped by lasers of two different wavelengths, and the tangential and radial polarization hollow fundamental frequency waves are generated by V-shaped cone mirrors, respectively; after frequency doubling by the negative uniaxial crystal cone and the positive uniaxial crystal cone, radial and tangential polarization hollow double-ring laser outputs are obtained, respectively. The double-ring vector frequency doubling laser with radial polarization in the inner ring and tangential polarization in the outer ring can realize the simultaneous capture of two different types of particles, and can also realize high-resolution imaging of the particles while realizing the particle capture.

Description

Technical Field

[0001] This invention relates to the field of laser technology, and in particular to a double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser. Technical Background

[0002] With the development of laser technology, people have proposed more types of laser beams according to practical needs, and hollow beams are one of them. They play an important role in optical imaging, optical trapping, optical information processing, electron acceleration, and optical manipulation of microscopic particles. At present, people have obtained hollow beams with different intensity distributions using passive methods such as phase method, nonlinear optics method, geometric optics method, mode conversion method, and computational holography. Passive methods change the spatial distribution of the Gaussian beam outside the resonant cavity, which is not the eigenmode of the laser. Not only is the light intensity contrast low, but the hollow beam will also quickly evolve into a solid beam as the propagation distance increases, that is, the hollow dark spot disappears quickly. In recent years, researchers have designed and implemented various forms of large-spot hollow lasers using active methods, such as anti-Gaussian hollow lasers (patent 201811357253.9), double-and-a-half anti-Gaussian hollow lasers (patent 201811357117.X), double-Gaussian hollow lasers, double-and-a-half Gaussian hollow lasers (patent 201811208397.8), and non-uniformly polarized hollow lasers (patent 201910065979.3). These hollow lasers not only possess large spot sizes and high contrast, but also exhibit the intrinsic modes of hollow beam lasers, ensuring that the beam does not become "not truly hollow" when propagating to the far field.

[0003] Besides intensity characteristics, polarization is another important feature of laser beams. In the past, research mainly focused on linearly polarized light, elliptically polarized light, and circularly polarized beams with uniform polarization states across the cross-section. With the development of laser technology, increasing attention is now being paid to beams with non-uniform spatial polarization, primarily rotationally symmetric polarization, such as radially polarized beams and tangentially polarized beams. Radially polarized light is 2-4 times more efficient than circularly polarized light in cutting the same metal, while tangentially polarized light has higher drilling efficiency. The polarization state of light also has a significant impact on plasma excitation; radially polarized light generates highly focused plasma on metal surfaces, forming a strong, localized, black, ring-shaped field effect. Radially polarized light, after passing through a high numerical aperture lens, can form a super-diffraction-limited, ultra-long subwavelength optical needle. In the field of scanning microscopy, using a subwavelength optical needle for scanning allows for the acquisition of information about a three-dimensional object in the vertical direction through lateral scanning alone, while maintaining subwavelength lateral resolution. In micro / nano fabrication, the subwavelength optical needle acts as a processing "knife," making it easier to fabricate structures with large aspect ratios and subwavelength lateral dimensions. Furthermore, subwavelength optical needles have significant applications in high-density data storage and particle trapping. On the other hand, tangentially polarized beams, after passing through a high numerical aperture lens, form an ultra-long high-potential-well optical tube, enabling more efficient particle trapping. Currently generated rotationally symmetric polarized hollow beams suffer from single polarization (either radial or tangential). If a dual-ring laser with both radial and tangential polarization is modulated and tightly focused, a light field distribution combining a subwavelength optical needle and a high-potential-well optical tube can be formed. This allows for both particle trapping and high-resolution imaging, greatly expanding the application of vector beams in the biomedical field. This invention fully utilizes the dual polarization characteristics of the inner ring tangential polarization and the outer ring radial polarization to achieve the simultaneous capture of two different types of particles, solving the technical problem that existing hollow beams can only capture a single type of particle.

[0004] With the continuous expansion of applications for hollow laser beams, extending the wavelength of the generated hollow laser beams to the visible and ultraviolet bands has gradually become a major research hotspot. This has enormous potential for broadening the cutting-edge applications of hollow lasers. For example, visible or ultraviolet hollow lasers have significant application demands in fields such as communications, biomedicine, optical sensing, spectroscopy, and high-end manufacturing. Currently, the most effective method to extend the laser wavelength output by a hollow laser to a shorter wavelength is to utilize optical frequency conversion of nonlinear optical crystals, such as self-mixing tunable hollow lasers (patent ZL201811357102.3). However, self-mixing provides two fundamental frequency waves from the same laser gain medium, resulting in a serious gain competition problem (patent ZL201910066066.3). Furthermore, the fundamental frequency waves provided by the same laser gain medium are limited, making it difficult to achieve the required mixing wavelength. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a dual-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser. This invention employs two pump sources with ring beams to pump the same laser gain medium, generating radially and tangentially polarized hollow fundamental frequency waves respectively. After frequency doubling, tangentially and radially polarized hollow dual-ring laser outputs are obtained. The dual-ring vector frequency-doubled laser with radial polarization of the inner ring and tangential polarization of the outer ring can simultaneously capture two different types of particles, and can also perform high-resolution imaging while capturing particles. The dual-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser has significant application value in fields such as communications, biomedicine, optical sensing, spectroscopy, and high-end manufacturing.

[0006] This invention is achieved through the following technical solution:

[0007] A dual-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser includes a first semiconductor laser array coupled to fiber and a second semiconductor laser array coupled to fiber (16);

[0008] The optical path of the first semiconductor laser array is provided with a first plano-convex lens, a first negative conical lens, a first positive axial conical lens, a first plane mirror, a positive uniaxial crystal cone, a second plane mirror, a laser gain medium, a V-shaped conical lens, a third plane mirror, and a third negative conical lens in sequence;

[0009] The optical path of the second semiconductor laser array is provided with a second plano-convex lens, a second negative conical lens, a second positive conical lens, and a second plane mirror in sequence.

[0010] The optical paths of the first semiconductor laser array and the second semiconductor laser array are perpendicular to each other.

[0011] The first plane mirror makes an angle of 45° with the horizontal plane, and the first and second plane mirrors are perpendicular to each other; the negative uniaxial crystal cone is located in the radiated light path of the first plane mirror;

[0012] The first semiconductor laser array emits a pump wavelength of λ. p1 The beam is collimated by the first plano-convex lens and then generated by the first negative conical lens to produce an axisymmetric parallel diverging beam. After being focused by the convex surface of the first positive conical lens, the parallel beams from different directions converge to a point. From the 2π direction, a circular focusing ring is formed on the focal plane of the first positive conical lens. The focusing ring beam is coupled into the laser gain medium by the first and second plane mirrors. When the distance between the first negative conical lens and the first positive conical lens is moved to adjust the size of the pump focal ring, the radius of the output radially polarized frequency-doubled hollow beam is adjusted.

[0013] The second semiconductor laser array emits a pump wavelength of λ. p2The beam is collimated by the second plano-convex lens and then generated into an axisymmetric parallel diverging beam by the second negative conical lens. It is then focused by the convex surface of the second positive conical lens, forming another circular focusing ring on the focal plane of the second positive conical lens. This focusing ring beam is coupled into the laser gain medium by the second plane mirror. By moving the distance between the second negative conical lens and the second positive conical lens to adjust the size of the pump focal ring, the radius of the output tangentially polarized frequency-doubled hollow beam can be adjusted.

[0014] The conical surface of the negative uniaxial crystal cone and the conical surface of the third negative conical mirror constitute a tangentially polarized fundamental frequency (or radially polarized frequency doubling) hollow laser resonator; the conical surface of the positive uniaxial crystal cone and the conical surface of the third negative conical mirror constitute a radially polarized fundamental frequency (or tangentially polarized frequency doubling) hollow laser resonator.

[0015] The gain competition between the tangentially polarized and radially polarized hollow fundamental frequency wavelengths is adjusted by changing the power of the pump wavelength or the distance between pump system components.

[0016] The third plane mirror is a double-ring frequency-doubled laser output coupling mirror.

[0017] The laser gain medium is pumped by two different wavelengths of laser rings, and tangentially and radially polarized hollow fundamental frequency waves are generated by V-shaped conical mirrors. After frequency doubling, orthogonally polarized radially and tangentially polarized hollow double-ring laser outputs are obtained respectively.

[0018] The cone angle of the negative uniaxial crystal cone and the third negative conical mirror. The fundamental frequency laser in the cavity forms a closed loop in the annular cavity. The two bottom surfaces of the V-shaped conical mirror are parallel and perpendicular to the system axis. When the incident angle θ of the laser beam on the outer cone surface of the V-shaped conical mirror is Brewster's angle, the fundamental frequency laser in the cavity is an S-wave. From the 2π direction (rotating one revolution along the system axis), the collection of S-waves forms tangentially polarized light. The negative uniaxial crystal cone is used as a frequency doubling crystal and is cut with a type I critical phase-matching angle. Then, each S-wave ray in the 2π direction becomes a P-wave after frequency doubling. From the 2π direction, the collection of P-waves forms a radially polarized frequency-doubled hollow laser.

[0019] When the cone angle χ = 90° of the positive uniaxial crystal cone, the fundamental frequency laser in the cavity forms a closed loop in the annular cavity, and when the incident θ of the laser beam on the inner cone surface of the V-shaped conical mirror... B When the Brewster angle is 2π, the fundamental frequency laser in the cavity is a P-wave. When viewed from the 2π direction (rotating one revolution along the system axis), the collection of P-waves forms a radially polarized hollow frequency-doubled laser. The radially polarized fundamental frequency light is cut by a positive uniaxial crystal cone using a type I critical phase-matching angle to generate a tangentially polarized frequency-doubled hollow laser.

[0020] The radius r1 of the pump focal ring is determined by the cone angles α and β of the first negative conical mirror and the first positive conical lens, as well as the focal length f1 of the first positive conical lens.

[0021]

[0022] r1=f1tanψ

[0023] ψ is the angle between the refracted ray of the pump beam on the conical surface of the first positive axis conical lens and the horizontal axis of the system, and n is the refractive index of the first negative conical lens and the first positive axis conical lens;

[0024] The radius r1 of the pump focal ring is determined by the cone angles ρ and δ of the second negative conical lens and the second positive conical lens, as well as the focal length f2 of the second positive conical lens.

[0025]

[0026] The light-transmitting surfaces of the first plano-convex lens, the first negative conical lens, and the first positive conical lens have a pump light wavelength λ. p1 Anti-reflective coating;

[0027] The light-transmitting surface of the first plane mirror faces the pump light wavelength λ. p1 Anti-reflective coating is applied, and a high-reflective coating is applied to the right side for the fundamental frequency wavelength;

[0028] The cone face of the negative uniaxial crystal cone is coated with a high-reflection film for the fundamental frequency wavelength and the second-harmonic frequency wavelength, and the bottom face is coated with an anti-reflection film for the fundamental frequency wavelength and the second-harmonic frequency wavelength.

[0029] The cone face of the positive uniaxial crystal cone is coated with a high-reflection film for the fundamental frequency wavelength and the second-harmonic wavelength, and the bottom face is coated with an anti-reflection film for the fundamental frequency wavelength and the second-harmonic wavelength.

[0030] The second plane mirror's optical path faces the pump light wavelength λ. p1 Antireflection coatings are applied to the fundamental and frequency-doubled wavelengths, with the right side corresponding to the pump wavelength λ. p2 High-reflectivity coating;

[0031] The light-transmitting surface of the laser gain medium has a pump light wavelength λ. p1 , λ p2 Antireflective coatings are applied to the wavelengths of fundamental and frequency-doubled light.

[0032] The cone angle γ of the V-shaped conical mirror satisfies γ=π-2arctann (n is the refractive index of the V-shaped conical mirror), and the two bottom surfaces are coated with anti-reflection films for the fundamental frequency wavelength and the second-order frequency wavelength.

[0033] The left end of the third plane mirror is coated with an anti-reflection film for the fundamental frequency wavelength and a high-reflection film for the second-order frequency wavelength, while the right end is coated with an anti-reflection film for the fundamental frequency wavelength.

[0034] The cone surface of the third negative conical mirror is coated with a high-reflectivity film for the fundamental frequency wavelength.

[0035] The light-transmitting surfaces of the second positive cone lens, the second negative cone lens, and the second plano-convex lens face the pump light wavelength λ. p2 Apply an anti-reflective coating.

[0036] The dual-ring vector frequency-doubled laser of the present invention, with inner ring radial polarization and outer ring tangential polarization, can simultaneously capture two different types of particles. Furthermore, it can perform high-resolution imaging while capturing particles. The dual-ring orthogonal rotationally symmetric polarized frequency-doubled hollow laser has significant application value in fields such as communications, biomedicine, optical sensing, spectroscopy, and high-end manufacturing. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the laser structure of the present invention;

[0038] Figure 2 A schematic diagram of a tangentially polarized hollow fundamental frequency laser generated by a V-shaped conical mirror;

[0039] Figure 3 A schematic diagram of radially polarized hollow fundamental frequency laser generated by a V-shaped conical mirror. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0041] A type of double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser, such as Figure 1 As shown, it includes a first semiconductor laser array 1 with fiber-coupled output and a second semiconductor laser array 16 with fiber-coupled output;

[0042] The optical path of the first semiconductor laser array 1 is provided with a first plano-convex lens 2, a first negative conical lens 3, a first positive axial conical lens 4, a first plane mirror 5, a positive uniaxial crystal cone 7, a second plane mirror 8, a laser gain medium 9, a V-shaped conical lens 10, a third plane mirror 11, and a third negative conical lens 12 in sequence.

[0043] The second semiconductor laser array 16 is provided with a second plano-convex lens 15, a second negative conical lens 14, a second positive conical lens 13, and a second plane mirror 8 in sequence along its optical path;

[0044] The optical paths of the first semiconductor laser array 1 and the second semiconductor laser array 16 are perpendicular to each other;

[0045] The first plane mirror 5 is at a 45° angle to the horizontal plane, and the first plane mirror 5 and the second plane mirror 8 are perpendicular to each other; the negative uniaxial crystal cone 6 is located on the light path of the first plane mirror 5.

[0046] The conical surface of the negative uniaxial crystal cone 6 and the conical surface of the third negative conical mirror 12 form a tangentially polarized fundamental frequency or radially polarized frequency-doubled hollow laser resonant cavity; the conical surface of the positive uniaxial crystal cone 7 and the conical surface of the third negative conical mirror 12 form a radially polarized fundamental frequency (or tangentially polarized frequency-doubled) hollow laser resonant cavity; the third plane mirror 11 is the output coupling mirror for the frequency-doubled hollow laser; the laser gain medium 9 is pumped by two different wavelengths of laser rings, and the V-shaped conical mirror 10 generates tangentially and radially polarized hollow fundamental frequency waves respectively. After being frequency-doubled by the negative uniaxial crystal cone 6 and the positive uniaxial crystal cone 7, radially and tangentially polarized hollow double-ring laser outputs are obtained respectively.

[0047] The first semiconductor laser array 1, coupled with fiber optic coupling, emits a pump wavelength of λ. p1 The beam is collimated by the first plano-convex lens 2 and then generated into an axisymmetric parallel diverging beam by the first negative conical lens 3. After being focused by the convex surface of the first positive conical lens 4, the parallel beams from different directions converge to a point, forming a circular focusing ring on the focal plane of the first positive conical lens 4 when viewed from the 2π direction. The focusing ring beam is coupled into the laser gain medium 9 through the first plane mirror 5 and the second plane mirror 8. The size of the pump focal ring can be adjusted by moving the distance between the first negative conical lens 3 and the first positive conical lens 4, which in turn can adjust the radius of the output radially polarized frequency-doubled hollow beam.

[0048] The second semiconductor laser array 16, coupled with fiber optic coupling, emits a pump wavelength of λ. p2 The beam is collimated by the second plano-convex lens 15 and then generated by the second negative conical lens 14 to produce an axisymmetric parallel diverging beam. It is then focused by the convex surface of the second positive conical lens 13, forming another circular focusing ring on the focal plane of the second positive conical lens 13. This focusing ring beam is coupled into the laser gain medium 9 by the second plane mirror 8. The size of the pump focal ring can be adjusted by moving the distance between the second negative conical lens 14 and the second positive conical lens 13, thereby adjusting the radius of the output tangentially polarized frequency-doubled hollow beam.

[0049] When the cone angle ω = σ = 90° of the negative uniaxial crystal cone 6 and the third negative conical mirror 12, the fundamental frequency laser in the cavity forms a closed loop in the annular cavity. The two bottom surfaces of the V-shaped conical mirror 10 are parallel and perpendicular to the system axis. When the laser beam is incident on the outer conical surface of the V-shaped conical mirror 10 at a distance θ... B At Brewster's angle, the fundamental frequency laser within the cavity is an S-wave. Viewed from the 2π direction (rotating one revolution along the system axis), the collection of S-waves forms tangentially polarized light, such as... Figure 2As shown. The negative uniaxial crystal cone 6, used as a frequency-doubling crystal, is cut at a type I critical phase-matching angle. Therefore, each S-wave ray in the 2π direction becomes a P-wave after frequency doubling. Viewed from the 2π direction, the collection of P-waves forms a radially polarized frequency-doubled hollow laser. Similarly, when the cone angle χ of the positive uniaxial crystal cone 7 is 90°, the fundamental frequency laser within the cavity forms a closed loop within the annular cavity. Furthermore, when the incident θ of the laser beam on the inner cone surface of the V-shaped conical mirror 10... B At Brewster's angle, the fundamental frequency laser within the cavity is a P-wave. Viewed from the 2π direction (rotating one revolution along the system axis), the collection of P-waves forms a radially polarized hollow frequency-doubled laser, such as... Figure 3 As shown, radially polarized fundamental frequency light is used to generate tangentially polarized frequency-doubled hollow laser by cutting a positive uniaxial crystal cone 7 with a type I critical phase-matching angle.

[0050] When tangentially and radially polarized hollow fundamental wavelengths utilize the same laser gain medium 9, a gain competition problem exists when the two resonant cavities are operating. Two methods can be used to balance the gain and loss between the two non-uniform polarization states (tangential and radial polarization) between the two resonant cavities:

[0051] The first scenario: By adjusting the pump wavelength and pump power of the first semiconductor laser array 1 or the second semiconductor laser array 16 coupled with the fiber, the gain of the two resonant cavities can be changed. That is, the cavity with higher loss can have its pump power increased, and the cavity with lower loss can have its pump power decreased.

[0052] The second scenario: When the fiber-coupled first semiconductor laser array 1 or the fiber-coupled second semiconductor laser array 16 has the same pump wavelength and pump power, this can be achieved by adjusting the distance between the first negative conical mirror 3 and the first positive axis conical lens 4, or between the second negative conical mirror 14 and the second positive axis conical lens 13. For example, adjusting the distance between the first negative conical mirror 3 and the first positive axis conical lens 4 changes the radius of the tangentially polarized S-wave fundamental frequency wave within the cavity, thereby changing the distance the fundamental frequency wave travels through the negative uniaxial crystal cone 6 in the direction perpendicular to the bottom surface (effective frequency doubling). The longer (smaller) the distance traveled, the higher (lower) the frequency doubling efficiency, and the greater (lower) the energy consumed by the fundamental frequency wave, thus adjusting the loss of the tangentially polarized fundamental frequency hollow laser resonator. Similarly, adjusting the distance between the second negative conical mirror 14 and the second positive axis conical lens 13 adjusts the loss of the radially polarized fundamental frequency hollow laser resonator. Therefore, by adjusting the losses of the two resonators (tangential and radial polarization directions), the gain and loss in the two polarization directions can be balanced.

[0053] Let the cone angles of the first negative conical mirror 3 and the first positive conical lens 4 be α and β, respectively; the focal length of the first positive conical lens 4 be f1; the refractive index of both the first negative conical mirror 3 and the first positive conical lens 4 be n; the angle between the refracted ray of the pump beam at the first positive conical lens 4 and the horizontal axis of the system be ψ; and the pump wavelength λ emitted by the fiber-coupled first semiconductor laser array 1. p1 If the radius of the pump coke ring in the gain medium 9 is r1, then the included angle ψ can be expressed as:

[0054]

[0055] The radius r1 of the pump coke ring can be expressed as:

[0056] r1=f1tanψ (2)

[0057] As can be seen from equations (1) and (2), the radius r1 of the pump focal ring is determined by the cone angles α and β of the first negative conical lens 3 and the first positive conical lens 4, as well as the focal length f1 of the first positive conical lens 4. Similarly, the radius r2 of the pump focal ring is determined by the cone angles ρ and δ of the second negative conical lens 14 and the second positive conical lens 13, as well as the focal length f2 of the second positive conical lens 13.

[0058]

[0059] When ρ≠α, δ≠β, or f1≠f2, the pump wavelength is λ. p1 and λ p2 The beam generates a focal ring in the laser gain medium 9 with a radius r1 ≠ r2, forming a double focal ring pump structure. When ρ = α, δ = β, or f1 = f2, the pump wavelength λ... p1 and λ p2 The beam produces a focal ring overlap in the laser gain medium 9, at which point the wavelength is λ. p1 and λ p2 A single coke ring mixing pump.

[0060] The light-transmitting surfaces of the first plano-convex lens 2, the first negative conical lens 3, and the first positive conical lens 4 have a pump light wavelength λ. p1 Anti-reflective coating; the first plane mirror 5 faces the pump light wavelength λ p1 Antireflection coatings are applied to the surface of the negative uniaxial crystal cone 6, with a high-reflection coating applied to both the fundamental and second-order harmonic wavelengths on the right side; antireflection coatings are applied to the bottom surface of the negative uniaxial crystal cone 6, with the bottom surface of the cone coated with both the fundamental and second-order harmonic wavelengths; high-reflection coatings are applied to the surface of the positive uniaxial crystal cone 7, with the bottom surface of the cone coated with both the fundamental and second-order harmonic wavelengths; the light-transmitting surface of the second plane mirror 8 faces the pump light wavelength λ. p1 Antireflection coatings are applied to the fundamental and frequency-doubled wavelengths, with the right side corresponding to the pump wavelength λ. p2High-reflectivity coating; the light-transmitting surface of laser gain medium 9 is aligned with the pump light wavelength λ. p1 , λ p2 Antireflection coatings are applied to the fundamental and second-order frequency wavelengths. The cone angle γ of the V-shaped conical mirror 10 satisfies γ = π - 2arctann (where n is the refractive index of the V-shaped conical mirror 10), and the two bottom surfaces are coated with antireflection coatings to the fundamental and second-order frequency wavelengths. The left end of the third plane mirror 11 is coated with an antireflection coating to the fundamental wavelength and a high-reflection coating to the second-order frequency wavelength, while the right end is coated with an antireflection coating to the fundamental wavelength. The cone surface of the third negative conical mirror 12 is coated with a high-reflection coating to the fundamental wavelength. The light-transmitting surfaces of the second positive conical lens 13, the second negative conical mirror 14, and the second plano-convex lens 15 are coated with a high-reflection coating to the pump light wavelength λ. p2 Apply an anti-reflective coating.

[0061] Example 1:

[0062] The following unit components can be used to realize a double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser: the specific parameters of the fiber-coupled first semiconductor laser array 1 are an output wavelength of 808nm, a fiber core diameter of 400μm, and a numerical aperture of 0.22; the first plano-convex lens 2, the first negative conical lens 3, the first positive conical lens 4, the first plane mirror 5, the second plane mirror 8, the V-shaped conical lens 10, the third plane mirror 11, the third negative conical lens 12, the second positive conical lens 13, the second negative conical lens 14, and the second plano-convex lens 15 are all made of K9 glass; the focal length of the first plano-convex lens 2 is 200 nm. The first negative conical mirror 3 has a cone angle α = 120°, and its light-transmitting surface is coated with an anti-reflection film at 808nm. The first positive conical lens 4 has a cone angle of 100° and a focal length of 300mm on its convex surface, and its light-transmitting surface is coated with an anti-reflection film at 808nm. The first plane mirror 5 is placed at a 45° angle along the horizontal direction, with its left end coated with an anti-reflection film at 808nm and its right end coated with an anti-reflection film at 808nm and a high-reflection film at 1064nm. The negative uniaxial crystal cone 6 is made of LiNbO3 and uses type I critical phase angle matching (phase matching angle θ = 90°). Its cone angle ω = 90°, the cone surface and the bottom surface are coated with a high-reflection film at 1064nm, and the bottom surface is coated with an anti-reflection film at 1064nm and 532nm; the positive uniaxial crystal cone 7 is made of KDP and adopts Type I critical phase angle matching (phase matching angle θ = 90°, The cone angle χ = 90°, the cone surface and bottom surface are coated with high-reflection films for 1064nm and 532nm, and the bottom surface is coated with anti-reflection films for 1064nm and 532nm; the second plane mirror 8 is placed at a 45° angle to the horizontal direction, the left end is coated with an anti-reflection film for 1064nm, the right end is coated with a high-reflection film for 885nm and an anti-reflection film for 1064nm; the gain medium is made of Nd:YAG crystal, Nd 3+The doping concentration is 1.0%, and the light-transmitting surface is coated with high-reflection films for 1064nm and 532nm; the V-shaped conical mirror 10 has a cone angle γ = 35.2°, and its two bottom surfaces are coated with high-reflection films for 1064nm and 532nm; the third plane mirror 11 is a 532nm output mirror, with an anti-reflection film coated on the left side for 1064nm and a high-reflection film coated on the 532nm side, and an anti-reflection film coated on the right side for 1064nm; the third negative conical mirror 12 has a cone angle σ = 90°, and its cone surface is coated with a high-reflection film for 808nm; the second The positive conical lens 13 has a cone angle of 100° and a focal length of 300mm on its convex surface. Its light-transmitting surface is coated with an anti-reflection coating at 885nm. The second negative conical lens 14 has a cone angle α = 120° and its light-transmitting surface is coated with an anti-reflection coating at 885nm. The second plano-convex lens 15 has a focal length of 200mm and its light-transmitting surface is coated with an anti-reflection coating at 885nm. The specific parameters of the fiber-coupled second semiconductor laser array 16 are: output wavelength of 885nm, fiber core diameter of 400μm, and numerical aperture of 0.22. Nd:YAG, LiNbO3, and KDP crystals are TEC cooled, with the temperature controlled within the range of 15°±0.5°.

[0063] Example 2:

[0064] The following unit components can be used to realize a double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser: the specific parameters of the fiber-coupled first semiconductor laser array 1 are an output wavelength of 479 nm, a fiber core diameter of 200 μm, and a numerical aperture of 0.22; the first plano-convex lens 2, the first negative conical lens 3, the first positive conical lens 4, the first plane mirror 5, the second plane mirror 8, the V-shaped conical lens 10, the third plane mirror 11, the third negative conical lens 12, the second positive conical lens 13, the second negative conical lens 14, and the second plano-convex lens 15 are all made of K9 glass; the focal length of the first plano-convex lens 2 is 200 nm. The first negative conical lens 3 has a cone angle α = 120°, and its light-transmitting surface is coated with an anti-reflection film at 479nm. The first positive conical lens 4 has a cone angle of 100° and a focal length of 100mm on its convex surface, and its light-transmitting surface is coated with an anti-reflection film at 479nm. The first plane mirror 5 is placed at a 45° angle along the horizontal direction, with its left end coated with an anti-reflection film at 808nm and its right end coated with an anti-reflection film at 479nm and a high-reflection film at 607nm. The negative uniaxial crystal cone 6 is made of KD2PO4 and uses Type I critical phase angle matching (phase matching angle θ = 90°). Its cone angle ω = 90°, the cone surface and the bottom surface are coated with a high-reflection film at 607nm, and the bottom surface is coated with an anti-reflection film at 607nm and 304nm; the positive uniaxial crystal cone 7 is made of BBO and adopts type I critical phase angle matching (phase matching angle θ = 90°, The cone angle χ = 90°, the cone surface and bottom surface are coated with high-reflection films for 607nm and 304nm, and the bottom surface is coated with anti-reflection films for 607nm and 304nm; the second plane mirror 8 is placed at a 45° angle to the horizontal direction, the left end is coated with an anti-reflection film for 607nm, the right end is coated with a high-reflection film for 444nm and an anti-reflection film for 607nm; the gain medium is made of Pr:YLF crystal, Pr 3+ The doping concentration is 1.0%, and the light-transmitting surface is coated with high-reflection films for 607nm and 304nm; the V-shaped conical mirror 10 has a cone angle γ = 34.2°, and its two bottom surfaces are coated with high-reflection films for 607nm and 304nm; the third plane mirror 11 is a 304nm output mirror, with an anti-reflection film coated on the left side for 607nm and a high-reflection film coated on the right side for 604nm; the third negative conical mirror 12 has a cone angle σ = 90°, and its cone surface is coated with a high-reflection film for 444nm; the second positive axis The cone lens 13 has a cone angle of 100° and a focal length of 100mm on its convex surface. Its light-transmitting surface is coated with an anti-reflection coating at 444nm. The second negative conical lens 14 has a cone angle α = 120° and its light-transmitting surface is coated with an anti-reflection coating at 444nm. The second plano-convex lens 15 has a focal length of 200mm and its light-transmitting surface is coated with an anti-reflection coating at 444nm. The specific parameters of the fiber-coupled second semiconductor laser array 16 are: output wavelength of 444nm, fiber core diameter of 200μm, and numerical aperture of 0.22. Pr:YLF, KD2PO4, and BBO crystals are TEC cooled, with the temperature controlled within the range of 15°±0.5°.

Claims

1. A double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser, characterized in that, Includes a first semiconductor laser array (1) with fiber-coupled output and a second semiconductor laser array (16) with fiber-coupled output. The first semiconductor laser array (1) is provided with a first plano-convex lens (2), a first negative conical lens (3), a first positive axis conical lens (4), a first plane mirror (5), a positive uniaxial crystal cone (7), a second plane mirror (8), a laser gain medium (9), a V-shaped conical lens (10), a third plane mirror (11), and a third negative conical lens (12) in sequence along its optical path. The second semiconductor laser array (16) is provided with a second plano-convex lens (15), a second negative conical lens (14), a second positive conical lens (13), and a second plane mirror (8) in sequence along its optical path. The optical paths of the first semiconductor laser array (1) and the second semiconductor laser array (16) are perpendicular to each other; The first plane mirror (5) makes an angle of 45° with the horizontal plane. o ， The first plane mirror (5) and the second plane mirror (8) are perpendicular to each other; the negative uniaxial crystal cone (6) is located on the light path of the first plane mirror (5); The first semiconductor laser array (1) emits a pump wavelength of λ. p1 The beam is collimated by the first plano-convex lens (2) and then generated by the first negative conical lens (3) to produce an axisymmetric parallel diverging beam. After being focused by the convex surface of the first positive conical lens (4), the parallel beams in different directions converge to a point. From the 2π direction, a circular focusing ring is formed on the focal plane of the first positive conical lens (4). The focusing ring beam is coupled into the laser gain medium (9) through the first plane mirror (5) and the second plane mirror (8). The laser gain medium (9) is pumped by two different wavelengths of laser rings and generated by the V-shaped conical lens (10) to produce tangential and radially polarized hollow fundamental frequency waves respectively. After frequency doubling, orthogonally polarized radial and tangentially polarized hollow double ring laser outputs are obtained respectively. When the distance between the first negative conical lens (3) and the first positive conical lens (4) is moved to adjust the size of the pump focal ring, the radius of the output radially polarized frequency-doubled hollow beam is adjusted. The second semiconductor laser array (16) emits a pump wavelength of λ. p2 The beam is collimated by the second plano-convex lens (15) and then the second negative conical lens (14) generates an axisymmetric parallel diverging beam. It is then focused by the convex surface of the second positive conical lens (13) and forms another circular focusing ring on the focal plane of the second positive conical lens (13). The focusing ring beam is coupled into the laser gain medium (9) by the second plane mirror (8). When the distance between the second negative conical lens (14) and the second positive conical lens (13) is moved to adjust the size of the pump focal ring, the radius of the output tangentially polarized frequency-doubled hollow beam is adjusted.

2. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The conical surface of the negative uniaxial crystal cone (6) and the conical surface of the third negative conical mirror (12) constitute a tangentially polarized fundamental frequency or radially polarized frequency-doubled hollow laser resonator; the conical surface of the positive uniaxial crystal cone (7) and the conical surface of the third negative conical mirror (12) constitute a radially polarized fundamental frequency or tangentially polarized frequency-doubled hollow laser resonator.

3. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 2, characterized in that, The gain competition between the tangentially polarized and radially polarized hollow fundamental frequency wavelengths is adjusted by changing the power of the pump wavelength or the distance between pump system components.

4. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The third plane mirror (11) is a double-ring frequency-doubling laser output coupling mirror.

5. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The cone angles ω=φ=90° of the negative uniaxial crystal cone (6) and the third negative conical mirror (12) are described. o The fundamental frequency laser in the cavity forms a closed loop in the annular cavity; the two bottom surfaces of the V-shaped conical mirror (10) are parallel and perpendicular to the system axis. When the incident angle θ of the laser beam on the outer cone surface of the V-shaped conical mirror (10) is Brewster angle, the fundamental frequency laser in the cavity is an S-wave. The collection of S-waves in the 2π direction forms tangentially polarized light; the negative uniaxial crystal cone (6) is cut with a type I critical phase matching angle as a frequency doubling crystal. Then, each S-wave ray in the 2π direction becomes a P-wave after frequency doubling. The collection of P-waves in the 2π direction forms a radially polarized frequency doubling hollow laser.

6. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The cone angle χ of the positive uniaxial crystal cone (7) is 90°. o The fundamental frequency laser within the cavity forms a closed loop in the annular cavity, and when the laser beam is incident on the inner conical surface of the V-shaped conical mirror (10) at angle θ... B When the Brewster angle is 2π, the fundamental frequency laser in the cavity is a P-wave. When viewed from the 2π direction (rotating one revolution along the system axis), the collection of P-waves forms a radially polarized hollow frequency-doubled laser. The radially polarized fundamental frequency light is cut by a positive uniaxial crystal cone (7) using a type I critical phase matching angle to generate a tangentially polarized frequency-doubled hollow laser.

7. The double-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The radius r1 of the pump focal ring is determined by the cone angles α and β of the cone surfaces of the first negative conical mirror (3) and the first positive axis conical lens (4) and the focal length f1 of the cone surface of the first positive axis conical lens (4): （1）， （2）， ψ is the angle between the refracted ray of the pump beam on the cone surface of the first positive axis conical lens (4) and the horizontal axis of the system, and n is the refractive index of the first negative conical lens (3) and the first positive axis conical lens (4); The radius r1 of the pump focal ring is determined by the cone angles ρ and δ of the second negative conical lens (14) and the second positive axis conical lens (13), as well as the focal length f2 of the second positive axis conical lens (13): （3）。 8. The dual-ring orthogonal rotationally symmetric polarization frequency-doubled hollow laser according to claim 1, characterized in that, The light-transmitting surfaces of the first plano-convex lens (2), the first negative conical lens (3), and the first positive conical lens (4) are aligned with the pump light wavelength λ. p1 Anti-reflective coating; The first plane mirror (5) faces the pump light wavelength λ. p1 Anti-reflective coating is applied, and a high-reflective coating is applied to the right side for the fundamental frequency wavelength; The cone face of the negative uniaxial crystal cone (6) is coated with a high-reflection film for the fundamental frequency wavelength and the second-order wavelength, and the bottom face is coated with an anti-reflection film for the fundamental frequency wavelength and the second-order wavelength. The cone face of the positive uniaxial crystal cone (7) is coated with a high-reflection film for the fundamental frequency wavelength and the second-order wavelength, and the bottom face is coated with an anti-reflection film for the fundamental frequency wavelength and the second-order wavelength. The second plane mirror (8) faces the pump light wavelength λ. p1 Antireflection coatings are applied to the fundamental and frequency-doubled wavelengths, with the right side corresponding to the pump wavelength λ. p2 High-reflectivity coating; The light-transmitting surface of the laser gain medium (9) has a pump light wavelength λ. p1 , λ p2 Antireflective coatings are applied to the wavelengths of fundamental and frequency-doubled light. The cone angle γ of the V-shaped conical mirror (10) satisfies (n is the refractive index of the V-shaped conical mirror (10), and the two bottom surfaces are coated with antireflective films for the fundamental wavelength and the second-order wavelength; The third plane mirror (11) has an anti-reflection coating on the left side facing the fundamental frequency wavelength and a high-reflection coating on the second-order frequency wavelength, and an anti-reflection coating on the right side facing the fundamental frequency wavelength. The cone surface of the third negative conical mirror (12) is coated with a high-reflectivity film for the fundamental frequency wavelength; The light-transmitting surfaces of the second positive cone lens (13), the second negative cone lens (14), and the second plano-convex lens (15) have a pump light wavelength λ. p2 Apply an anti-reflective coating.

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