A laser for generating cylindrical vector beams

Abstract

The present application discloses a laser for generating a cylindrical vector light beam. The laser for generating a cylindrical vector light beam generates a linearly polarized light-like noise-locked mode pulse based on a nonlinear polarization rotation technology through the mutual cooperation of a pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit, and adjusts the polarization state of the linearly polarized light-like noise-locked mode pulse through the beam forming unit, and finally obtains a cylindrical vector light beam with a preset polarization distribution. The design is simple and easy to implement, and is conducive to simplifying the structure of the laser for generating a cylindrical vector light beam.

Description

[0001] This application claims priority to a Chinese patent application filed with the China Patent Office on August 24, 2020, with application number 202010856655.4 and invention name “A laser for generating a cylindrical vector beam”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of laser technology, and more particularly to a laser for generating a cylindrical vector beam. Background Art

[0003] The physical image of light polarization is the electric field polarization phenomenon of light waves in the direction perpendicular to the propagation of light. The polarization control of light is an important part of light field control.

[0004] Research on beam polarization in the field of optics generally focuses on traditional uniformly polarized beams, that is, the polarization state corresponding to any position in the light field is the same (for example: linear polarization, circular polarization, and random polarization including natural light). The difference between cylindrical vector beams and traditional beams is that their polarization direction presents a non-uniform polarization distribution on the cross section perpendicular to the propagation direction. Because their polarization distribution is symmetrical about the central axis of the light field, they are called axisymmetric vector beams. According to their polarization distribution characteristics, they are generally divided into three types: radially polarized beams, angularly polarized beams, and mixed polarized beams. Because of their unique polarization characteristics and annular spot distribution, cylindrical vector polarized beams have strong application prospects in the fields of particle acceleration, metal particle manipulation, laser processing, and surface plasma excitation under strong focusing conditions.

[0005] In the decades since the concept of cylindrical vector beams was proposed in 1972, many methods have been reported to generate cylindrical vector beams, but the structures of existing cylindrical vector beam laser systems are mostly complex. Summary of the invention

[0006] In order to solve the above technical problems, the present application provides a laser for generating a cylindrical vector light beam, so as to solve the problem that the structure of the laser for generating a cylindrical vector light beam is relatively complex.

[0007] To achieve the above technical objectives, the present application provides the following technical solutions:

[0008] A laser for generating a cylindrical vector beam, comprising: a pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit; wherein:

[0009] The pump light generating unit is used to generate pump light of a first polarization state and transmit the pump light to the space link unit;

[0010] The spatial link unit is used to receive the modulated light or the pump light, perform polarization state conversion and narrowing processing on the pump light and the modulated light, obtain the light to be processed and transmit it to the optical fiber link unit, and couple the modulated light that meets the requirements to obtain the imaging pulse of the second polarization state and transmit it to the beam forming unit; the imaging pulse includes a linearly polarized light noise-like mode-locked pulse;

[0011] The optical fiber link unit is used to amplify, self-phase modulate and cross-phase modulate the light to be processed to obtain the modulated light in the second polarization state and transmit it to the spatial link unit;

[0012] The beam forming unit is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector beam with a preset polarization distribution.

[0013] Optionally, the pump light generating unit comprises: a pump source, a first lens group and a dichroic mirror; wherein,

[0014] The pump source is used to emit pump light in a first polarization state;

[0015] The first lens group is used for collimating and focusing the pump light in the first polarization state and then transmitting it to the dichroic mirror;

[0016] The dichroic mirror is used to couple the collimated and focused pump light into the space link unit.

[0017] Optionally, the first lens group includes: a first lens and a second lens;

[0018] Wherein, the first lens is used to collimate the pump light in the first polarization state;

[0019] The second lens is used to focus the pump light in the first polarization state after the collimation process.

[0020] Optionally, both the first lens and the second lens are plano-convex lenses, and the convex surfaces of the first lens and the second lens are opposite to each other.

[0021] Optionally, the space link unit includes: a third lens, a first quarter wave plate, a half wave plate, a polarization beam splitter prism, a second quarter wave plate and a fourth lens; wherein,

[0022] The third lens, the first quarter wave plate, the half wave plate, the polarization beam splitter prism, the second quarter wave plate and the fourth lens are arranged in sequence along the first direction, and the optical axes of the third lens, the first quarter wave plate, the half wave plate, the polarization beam splitter prism, the second quarter wave plate and the fourth lens are arranged along a straight line parallel to the first direction;

[0023] The third lens is used to collimate the pump light or the modulated light;

[0024] The first quarter wave plate and the half wave plate constitute a polarization control module, and the polarization control module is used to make the polarization state of the peak part of the pump light or the modulated light consistent with a preset polarization state, and the preset polarization state is the polarization state of the polarized light allowed to pass through by the polarization beam splitter prism;

[0025] The polarization beam splitter prism is used to convert the polarization state of the pump light or the modulated light passing through the polarization control module into the second polarization state, and emit the pump light or the modulated light after the polarization state conversion to the second quarter wave plate through the first output surface to narrow the pump light or the modulated light, and to convert the modulated light that meets the requirements into a pulse to be imaged in the second polarization state and couple it to the beam forming unit through the second output surface;

[0026] The second quarter wave plate is used to convert the polarization state of the pump light or the modulated light having the second polarization state into the first polarization state, and transmit it to the fourth lens, so that the fourth lens couples the pump light or the modulated light having the first polarization state into the optical fiber link unit.

[0027] Optionally, the optical fiber link unit comprises: a single-mode optical fiber, a polarization-independent isolator and an erbium-ytterbium co-doped single-mode optical fiber; wherein,

[0028] One end of the single-mode optical fiber is used to receive the pump light or the modulated light emitted from the fourth lens, and the other end of the single-mode optical fiber is connected to one end of the erbium-ytterbium co-doped single-mode optical fiber;

[0029] The polarization-independent isolator is arranged in the single-mode optical fiber, and the isolation direction of the polarization-independent isolator is directed from the single-mode optical fiber to the erbium-ytterbium co-doped single-mode optical fiber;

[0030] One end of the erbium-ytterbium co-doped single-mode optical fiber away from the single-mode optical fiber is directed toward the space link unit;

[0031] The pump light is amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber and the erbium-ytterbium co-doped single-mode optical fiber to form a modulated light of the second polarization state, and then is transmitted to the dichroic mirror;

[0032] The modulated light is transmitted to the dichroic mirror after being amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber and the erbium-ytterbium co-doped single-mode optical fiber.

[0033] Optionally, the beam forming unit comprises: a vortex wave plate;

[0034] The vortex wave plate is arranged on the side of the second output surface of the polarization beam splitter prism, and the vortex wave plate is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector light beam with a preset polarization distribution. The preset polarization distribution is related to the fast axis of the vortex wave plate and the vibration direction of the pulse to be imaged.

[0035] Optionally, the beam forming unit is further used to detect polarization distribution of the cylindrical vector beam.

[0036] Optionally, the beam forming unit further comprises: a Glan prism and a beam quality analyzer;

[0037] The Glan prism is arranged on a side of the vortex wave plate away from the polarization beam splitter prism, and the beam quality analyzer is arranged on a side of the Glan prism away from the vortex wave plate;

[0038] The Glan prism is used to analyze the cylindrical vector light beam;

[0039] The beam quality analyzer is used to perform a light field distribution test on the polarized cylindrical vector beam.

[0040] Optionally, the vortex wave plate is a zero-order vortex wave plate.

[0041] It can be seen from the above technical scheme that the embodiment of the present application provides a laser for generating a cylindrical vector light beam. The laser for generating a cylindrical vector light beam generates a linearly polarized light-like noise-locked mode pulse based on the nonlinear polarization rotation technology through the mutual cooperation of a pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit, and adjusts the polarization state of the linearly polarized light-like noise-locked mode pulse through the beam forming unit, and finally obtains a cylindrical vector light beam with a preset polarization distribution. The design is simple and easy, which is conducive to simplifying the structure of the laser for generating a cylindrical vector light beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0043] Figure 1 A laser for generating a cylindrical vector beam is provided in one embodiment of the present application;

[0044] Figure 2 A schematic diagram of a linearly polarized light noise-like mode-locked pulse output by a polarization beam splitter prism provided in one embodiment of the present application;

[0045] Figure 3 A schematic diagram of the principle of obtaining a cylindrical vector beam with arbitrary polarization distribution by changing the angle between the vibration direction of the pulse to be imaged and the fast axis of the vortex wave plate;

[0046] Figure 4 A schematic diagram of light field distribution of a cylindrical vector light beam in a representative direction provided for an embodiment of the present application. DETAILED DESCRIPTION

[0047] As described in the background technology, most of the methods for generating cylindrical vector beams in the prior art use intracavity mode selection elements or polarization selection elements to force the laser to operate in an axisymmetric polarization mode, including birefringent crystals or anisotropic crystals to suppress the fundamental mode advantage; or use phase diffraction elements or polarization selection cavity mirrors and other elements on micrometer and nanometer scales; or use Sagnac interference devices to generate cylindrical vector beams. In addition, the generation of cylindrical vector beams can be achieved by changing the pump structure to achieve the gain advantage of high-order modes. Passive methods are often used to generate cylindrical vector beams in free space. Generally, such methods convert uniformly polarized beams into spatially non-uniform axisymmetric polarization states, so the elements usually need to have spatial axisymmetric characteristics for polarization states. Common methods can use a combination of radial polarizers and vortex phase compensators; or spatial light modulators; or use spatial axisymmetric sub-wavelength spatial gratings; or a more direct combination of half-wave plates (vortex half-wave plates vortex vortex wave plates). This method can improve polarization purity, but the laser system becomes more complicated. Moreover, when the pump power increases, the difficulty of controlling the beam mode will increase.

[0048] In view of this, an embodiment of the present application provides a laser for generating a cylindrical vector beam, comprising: a pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit; wherein,

[0049] The pump light generating unit is used to generate pump light of a first polarization state and transmit the pump light to the space link unit;

[0050] The spatial link unit is used to receive the modulated light or the pump light, perform polarization state conversion and narrowing processing on the pump light and the modulated light, obtain the light to be processed and transmit it to the optical fiber link unit, and couple the modulated light that meets the requirements to obtain the imaging pulse of the second polarization state and transmit it to the beam forming unit; the imaging pulse includes a linearly polarized light noise-like mode-locked pulse;

[0051] The optical fiber link unit is used to amplify, self-phase modulate and cross-phase modulate the light to be processed to obtain the modulated light in the second polarization state and transmit it to the spatial link unit;

[0052] The beam forming unit is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector beam with a preset polarization distribution.

[0053] The laser for generating a cylindrical vector beam generates a linearly polarized light-like noise-locked mode pulse based on a nonlinear polarization rotation technology through the cooperation of a pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit, and adjusts the polarization state of the linearly polarized light-like noise-locked mode pulse through the beam forming unit, so as to finally obtain a cylindrical vector beam with a preset polarization distribution. The design is simple and easy to implement, and is conducive to simplifying the structure of the laser for generating a cylindrical vector beam.

[0054] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0055] The present application embodiment provides a laser for generating a cylindrical vector beam, such as Figure 1 As shown, it includes: a pump light generating unit 100, a space link unit 300, an optical fiber link unit 400 and a beam forming unit 200; wherein,

[0056] The pump light generating unit 100 is used to generate pump light of a first polarization state and transmit the pump light to the space link unit 300;

[0057] The spatial link unit 300 is used to receive the modulated light or the pump light, convert the polarization state of the pump light and the modulated light, and perform narrowing processing to obtain the light to be processed and transmit it to the optical fiber link unit 400, and to couple and output the modulated light that meets the requirements to obtain the imaging pulse of the second polarization state and transmit it to the beam forming unit 200; the imaging pulse includes a linearly polarized light noise-like mode-locked pulse;

[0058] The optical fiber link unit 400 is used to amplify, self-phase modulate and cross-phase modulate the light to be processed to obtain the modulated light in the second polarization state and transmit it to the space link unit 300;

[0059] The beam forming unit 200 is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector beam with a preset polarization distribution.

[0060] Specifically, in this embodiment, we refer to the light emitted from the space link unit 300 to the optical fiber link unit 400 as the light to be processed, and the light emitted from the optical fiber link unit 400 to the space link unit 300 is usually modulated light.

[0061] The polarization state conversion of the pump light and the modulated light by the space link unit 300 mainly includes conversion from a first polarization state to a second polarization state and conversion from the second polarization state to a first polarization state, wherein the first polarization state may be an elliptical polarization state and the second polarization state may be a linear polarization state. In the polarization state conversion process of the space link unit 300, narrowing processing can be achieved by setting a polarization beam splitter prism 18 in the interval between two polarization state conversions. Specifically, when the polarization state of the pump light or the modulated light is converted from the first polarization state to the second polarization state, the polarization state of the peak part of the pulse (pump light or modulated light) in the second polarization state can be controlled to be consistent with the polarization state allowed to pass by the polarization beam splitter prism 18, so that when the pulse of the second polarization state passes through the polarization beam splitter prism 18, only the peak part can pass through, while the edge part cannot pass through the polarization beam splitter prism 18 completely, thereby achieving the purpose of narrowing.

[0062] The feasible structures of each unit in the embodiments of the present application are described below.

[0063] Still reference Figure 1 Optionally, the pump light generating unit 100 comprises: a pump source 10, a first lens group and a dichroic mirror 13; wherein,

[0064] The pump source 10 is used to emit pump light in a first polarization state;

[0065] The first lens group is used for collimating and focusing the pump light in the first polarization state and then transmitting it to the dichroic mirror 13;

[0066] The dichroic mirror 13 is used to couple the collimated and focused pump light into the space link unit 300 .

[0067] The pump source 10 may be a semiconductor laser, the output wavelength of which may be 975 nm, with a pigtail output having a numerical aperture of 0.22 and a diameter of 105 μm.

[0068] The first lens group may include: a first lens 11 and a second lens 12;

[0069] Wherein, the first lens 11 is used to collimate the pump light in the first polarization state;

[0070] The second lens 12 is used to focus the collimated pump light in the first polarization state.

[0071] The first lens 11 may also be called a pump light collimating lens, and the second lens 12 may also be called a pump light focusing lens. The first lens 11 and the second lens 12 may both be plano-convex lenses, and the convex surfaces of the first lens 11 and the second lens 12 are opposite to each other. The focal length may be selected to be 50 mm, and an anti-reflection film is coated at 650-1050 nm, that is, the anti-reflection film has an anti-reflection effect on light of 650-1050 nm.

[0072] The surface of the dichroic mirror 13 may be coated with a high-transmittance film and a high-reflection film. The high-transmittance film has a high-transmittance property within a wavelength range of 900-1050nm, and the high-reflection film has a high-reflection property within a wavelength range of 1500-1700nm.

[0073] For the space link unit 300, still refer to Figure 1 The space link unit 300 includes: a third lens 15, a first quarter wave plate 16, a half wave plate 17, a polarization beam splitter prism 18, a second quarter wave plate 19 and a fourth lens 25; wherein,

[0074] The third lens 15, the first quarter wave plate 16, the half wave plate 17, the polarization beam splitter prism 18, the second quarter wave plate 19 and the fourth lens 25 are arranged in sequence along the first direction, and the optical axes of the third lens 15, the first quarter wave plate 16, the half wave plate 17, the polarization beam splitter prism 18, the second quarter wave plate 19 and the fourth lens 25 are arranged along a straight line parallel to the first direction;

[0075] The third lens 15 is used to collimate the pump light or the modulated light;

[0076] The first quarter wave plate 16 and the half wave plate 17 constitute a polarization control module, and the polarization control module is used to make the polarization state of the peak part of the pump light or the modulated light consistent with a preset polarization state, and the preset polarization state is the polarization state of the polarized light allowed to pass through by the polarization beam splitter prism 18;

[0077] The polarization beam splitter prism 18 is used to convert the polarization state of the pump light or the modulated light passing through the polarization control module into the second polarization state, and emit the pump light or the modulated light after the polarization state conversion to the second quarter wave plate 19 through the first output surface to narrow the pump light or the modulated light, and to convert the modulated light that meets the requirements into the imaging pulse of the second polarization state and couple it to the beam forming unit 200 through the second output surface;

[0078] The second quarter-wave plate 19 is used to convert the polarization state of the pump light or the modulated light with the second polarization state into the first polarization state, and transmit it to the fourth lens 25, so that the fourth lens 25 couples the pump light or the modulated light with the first polarization state into the optical fiber link unit 400.

[0079] In this embodiment, the combination of the first quarter wave plate 16 and the half wave plate 17 can traverse all polarization states. The polarization control module composed of the first quarter wave plate 16 and the half wave plate 17 is equivalent to a polarization controller, but its volume is much smaller than that of a traditional polarization controller, which is conducive to the miniaturization of the laser used to generate a cylindrical vector light beam.

[0080] In this embodiment, the fast axis directions of the first quarter wave plate 16 and the half wave plate 17 can be adjusted so that the polarization state of the peak part of the optical pulse passing through the polarization control module composed of the first quarter wave plate 16 and the half wave plate 17 is consistent with the preset polarization state. The preset polarization state is the polarization state of the polarized light allowed to pass through by the polarization beam splitter prism 18, and the edge part of the optical pulse cannot pass through the polarization beam splitter prism 18 due to the different phase shift accumulation, thereby narrowing the optical pulse. In such a ring resonant cavity composed of a combination of an optical fiber link unit 400 and a spatial link unit 300, the optical pulse is repeatedly narrowed and amplified again and again under the action of the erbium-ytterbium co-doped single-mode optical fiber 14, and finally a balance between gain and loss is achieved. Then, the polarization beam splitter prism 18 couples and outputs a linearly polarized light noise-like mode-locked pulse. The linearly polarized light noise-like mode-locked pulse output by the polarization beam splitter prism 18 can be as shown in Figure 2 shown.

[0081] The third lens 15 and the fourth lens 25 may both be plano-convex lenses, with a focal length of 20 mm, and may be coated with an anti-reflection film on the surface, which has anti-reflection properties within a wavelength range of 1050-1700 nm.

[0082] The surfaces of the first quarter wave plate 16 and the second quarter wave plate 19 may be coated with an anti-reflection film, and the anti-reflection film has an anti-reflection characteristic within a wavelength range of 1500-1700 nm.

[0083] The surface of the half wave plate 17 may be coated with an anti-reflection film, and the anti-reflection film has anti-reflection properties within a wavelength range of 1500-1700 nm.

[0084] For the optical fiber link unit 400, still refer to Figure 1 The optical fiber link unit 400 includes: a single-mode optical fiber 24, a polarization-independent isolator 23 and an erbium-ytterbium co-doped single-mode optical fiber 14; wherein,

[0085] One end of the single-mode optical fiber 24 is used to receive the pump light or the modulated light emitted from the fourth lens 25, and the other end of the single-mode optical fiber 24 is connected to one end of the erbium-ytterbium co-doped single-mode optical fiber 14;

[0086] The polarization-independent isolator 23 is disposed in the single-mode optical fiber 24, and the isolation direction of the polarization-independent isolator 23 is directed from the single-mode optical fiber 24 to the erbium-ytterbium co-doped single-mode optical fiber 14;

[0087] One end of the erbium-ytterbium co-doped single-mode optical fiber 14 away from the single-mode optical fiber 24 is oriented toward the space link unit 300;

[0088] The pump light is amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber 24 and the erbium-ytterbium co-doped single-mode optical fiber 14 to form a modulated light of the second polarization state, which is transmitted to the dichroic mirror 13;

[0089] The modulated light is transmitted to the dichroic mirror 13 after being amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber 24 and the erbium-ytterbium co-doped single-mode optical fiber 14 .

[0090] The length of the Er-Yb co-doped single-mode optical fiber 14 can be selected to be about 1 m, the dispersion at a wavelength of 1560 nm can be selected to be -48 ps / nm / km, the core numerical aperture is 0.18, the cladding diameter can be 125 μm, and the surface can be coated with a low refractive index polymer material.

[0091] The polarization-independent isolator 23 may be a fiber isolator, and the maximum damage threshold may be 500 mW.

[0092] For the beam forming unit 200, optionally, still refer to Figure 1 , the beam forming unit 200 comprises: a vortex wave plate 20;

[0093] The vortex wave plate 20 is arranged on the side of the second output surface of the polarization beam splitter prism 18. The vortex wave plate 20 is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector beam with a preset polarization distribution. The preset polarization distribution is related to the fast axis of the vortex wave plate 20 and the vibration direction of the pulse to be imaged.

[0094] Specifically, a cylindrical vector beam with arbitrary polarization distribution can be obtained by changing the angle between the vibration direction of the pulse to be imaged and the fast axis of the vortex wave plate 20. The specific principle is as follows: Figure 3 As shown, Figure 3VMP represents the vortex wave plate 20, the arrow in the circular figure on the left side of the vortex wave plate 20 represents the vibration direction of the pulse to be imaged, and the arrow in the prototype figure on the right side of the vortex wave plate 20 represents the vibration direction of the cylindrical vector beam. The vortex wave plate 20 has a constant delay over the entire transparent aperture, but the direction of its fast axis is continuously selected over the entire area of ​​the optical element, which can be expressed as:

[0095]

[0096] in is the azimuth, When . is the direction of the fast axis. m is the order of the vortex wave plate 20, which defines the polarization order of the cylindrical vector beam. It has a 2mπ polarization rotation along the clockwise circumferential direction. The Jones matrix of the vortex wave plate 20 can be expressed as:

[0097]

[0098] When we use linearly polarized light (Jones matrix is , represents the direction of the incident linearly polarized light relative to the x-axis), then the output electric field should satisfy:

[0099]

[0100] The above formula indicates that each point on the cross section of the output beam after passing through the vortex wave plate 20 with any polarization direction is linearly polarized, but the polarization direction depends on the azimuth angle. .

[0101] According to the above principle, we will use Glan prism 21 as an analyzer to change the azimuth angle of the vortex half-wave plate (where is the angle between the fast axis of the vortex wave plate and the linear polarized light coming out of the PBS) and then the cylindrical vector beam with any polarization direction can be observed through the CCD. Figure 4 is the light field distribution of a cylindrical vector beam in a representative direction, Figure 4 middle, RadialPolarization Mode represents the light field distribution of the radial cylindrical vector beam. Radial PolarizationMode represents the light field distribution of a clockwise cylindrical vector beam. Radial Polarization Mode represents the light field distribution of the angular cylindrical vector beam. Radial Polarization Mode represents the light field distribution of a counterclockwise cylindrical vector beam.

[0102] The vortex wave plate 20 can be selected as a zero-order vortex wave plate 20, with m=1 and a wavelength of 1550nm.

[0103] Optionally, the beam forming unit 200 is further used to detect polarization distribution of the cylindrical vector beam.

[0104] That is, optionally, the beam forming unit 200 further includes: a Glan prism 21 and a beam quality analyzer 22;

[0105] The Glan prism 21 is disposed on a side of the vortex wave plate 20 away from the polarization beam splitter prism 18, and the beam quality analyzer 22 is disposed on a side of the Glan prism 21 away from the vortex wave plate 20;

[0106] The Glan prism 21 is used to analyze the cylindrical vector light beam;

[0107] The beam quality analyzer 22 is used to perform a light field distribution test on the polarized cylindrical vector beam.

[0108] exist Figure 1 In the overall structure shown, the space link unit 300 and the optical fiber link unit 400 form a ring cavity structure along the direction of the polarization-independent isolator 23 (counterclockwise), and a combination of erbium-ytterbium co-doped gain fiber and single-mode fiber 24 is used to achieve a balance between dispersion and nonlinearity to realize mode locking.

[0109] After a large number of experimental verifications, the design scheme of the present invention is feasible. The noise-like Er-Yb co-doped mode-locked fiber laser device for generating cylindrical vector beams provided by the present invention has a simple design, low insertion loss, high efficiency, and is also suitable for high-energy operation.

[0110] In summary, the embodiment of the present application provides a laser for generating a cylindrical vector beam. The laser for generating a cylindrical vector beam generates a linearly polarized light-like noise-locked mode pulse based on the nonlinear polarization rotation technology through the cooperation of a pump light generating unit 100, a spatial link unit 300, an optical fiber link unit 400 and a beam forming unit 200, and adjusts the polarization state of the linearly polarized light-like noise-locked mode pulse through the beam forming unit 200, and finally obtains a cylindrical vector beam with a preset polarization distribution. The design is simple and easy to implement, which is conducive to simplifying the structure of the laser for generating a cylindrical vector beam.

[0111] The features described in the embodiments of the present specification may be replaced or combined with each other. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments may be referenced to each other.

[0112] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A laser for generating a cylindrical vector beam, characterized in that: include: A pump light generating unit, a space link unit, an optical fiber link unit and a beam forming unit; wherein, The pump light generating unit is used to generate pump light in a first polarization state and transmit the pump light to the space link unit; The spatial link unit is used to receive the modulated light or the pump light, perform polarization state conversion and narrowing processing on the pump light and the modulated light, obtain the light to be processed and transmit it to the optical fiber link unit, and couple the modulated light that meets the requirements to obtain the imaging pulse of the second polarization state and transmit it to the beam forming unit; the imaging pulse includes a linearly polarized light noise-like mode-locked pulse; The optical fiber link unit is used to amplify, self-phase modulate and cross-phase modulate the light to be processed to obtain the modulated light in the second polarization state and transmit it to the spatial link unit; The beam forming unit is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector beam with a preset polarization distribution; the pump light generating unit includes: a pump source, a first lens group and a dichroic mirror; wherein, The pump source is used to emit pump light in a first polarization state; The first lens group is used for collimating and focusing the pump light in the first polarization state and then transmitting it to the dichroic mirror; The dichroic mirror is used to couple the collimated and focused pump light into the space link unit; The space link unit comprises: a third lens, a first quarter wave plate, a half wave plate, a polarization beam splitter prism, a second quarter wave plate and a fourth lens; wherein, The third lens, the first quarter wave plate, the half wave plate, the polarization beam splitter prism, the second quarter wave plate and the fourth lens are arranged in sequence along the first direction, and the optical axes of the third lens, the first quarter wave plate, the half wave plate, the polarization beam splitter prism, the second quarter wave plate and the fourth lens are arranged along a straight line parallel to the first direction; The third lens is used to collimate the pump light or the modulated light; The first quarter wave plate and the half wave plate constitute a polarization control module, and the polarization control module is used to make the polarization state of the peak part of the pump light or the modulated light consistent with a preset polarization state, and the preset polarization state is the polarization state of the polarized light allowed to pass through by the polarization beam splitter prism; The polarization beam splitter prism is used to convert the polarization state of the pump light or the modulated light passing through the polarization control module into the second polarization state, and emit the pump light or the modulated light after the polarization state conversion to the second quarter wave plate through the first output surface to narrow the pump light or the modulated light, and to convert the modulated light that meets the requirements into a pulse to be imaged in the second polarization state and couple it to the beam forming unit through the second output surface; The second quarter wave plate is used to convert the polarization state of the pump light or the modulated light having the second polarization state into the first polarization state, and transmit the polarization state to the fourth lens, so that the fourth lens couples the pump light or the modulated light having the first polarization state into the optical fiber link unit; The optical fiber link unit comprises: a single-mode optical fiber, a polarization-independent isolator and an erbium-ytterbium co-doped single-mode optical fiber; wherein, One end of the single-mode optical fiber is used to receive the pump light or the modulated light emitted from the fourth lens, and the other end of the single-mode optical fiber is connected to one end of the erbium-ytterbium co-doped single-mode optical fiber; The polarization-independent isolator is arranged in the single-mode optical fiber, and the isolation direction of the polarization-independent isolator is directed from the single-mode optical fiber to the erbium-ytterbium co-doped single-mode optical fiber; the polarization-independent isolator is a fiber isolator; One end of the erbium-ytterbium co-doped single-mode optical fiber away from the single-mode optical fiber is directed toward the space link unit; The pump light is amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber and the erbium-ytterbium co-doped single-mode optical fiber to form a modulated light of the second polarization state, and then is transmitted to the dichroic mirror; The modulated light is transmitted to the dichroic mirror after being amplified, self-phase modulated and cross-phase modulated by the single-mode optical fiber and the erbium-ytterbium co-doped single-mode optical fiber.

2. The laser for generating a cylindrical vector beam according to claim 1, characterized in that: The first lens group includes: a first lens and a second lens; Wherein, the first lens is used to collimate the pump light in the first polarization state; The second lens is used to focus the pump light in the first polarization state after the collimation process.

3. The laser for generating a cylindrical vector beam according to claim 2, characterized in that: The first lens and the second lens are both plano-convex lenses, and the convex surfaces of the first lens and the second lens are opposite to each other.

4. The laser for generating a cylindrical vector beam according to claim 1, characterized in that: The beam forming unit comprises: a vortex wave plate; The vortex wave plate is arranged on the side of the second output surface of the polarization beam splitter prism, and the vortex wave plate is used to adjust the polarization state of the pulse to be imaged to obtain a cylindrical vector light beam with a preset polarization distribution. The preset polarization distribution is related to the fast axis of the vortex wave plate and the vibration direction of the pulse to be imaged.

5. The laser for generating a cylindrical vector beam according to claim 4, characterized in that: The beam forming unit is also used to detect the polarization distribution of the cylindrical vector beam.

6. The laser for generating a cylindrical vector beam according to claim 5, characterized in that: The beam forming unit further comprises: a Glan prism and a beam quality analyzer; The Glan prism is arranged on a side of the vortex wave plate away from the polarization beam splitter prism, and the beam quality analyzer is arranged on a side of the Glan prism away from the vortex wave plate; The Glan prism is used to analyze the cylindrical vector light beam; The beam quality analyzer is used to perform a light field distribution test on the polarized cylindrical vector beam.

7. The laser for generating a cylindrical vector beam according to claim 5, characterized in that: The vortex wave plate is a zero-order vortex wave plate.

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