CN114784606A - Laguerre Gaussian beam generating device and method - Google Patents

Laguerre Gaussian beam generating device and method Download PDF

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CN114784606A
CN114784606A CN202210291199.2A CN202210291199A CN114784606A CN 114784606 A CN114784606 A CN 114784606A CN 202210291199 A CN202210291199 A CN 202210291199A CN 114784606 A CN114784606 A CN 114784606A
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laser
light
concave
polarized light
vortex
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赵永光
贾代文
周晶晶
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Jiangsu Normal University
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/164—Solid materials characterised by a crystal matrix garnet
    • H01S3/1643—YAG
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/10—Controlling the intensity, frequency, phase, polarisation or direction of the emitted radiation, e.g. switching, gating, modulating or demodulating
    • H01S3/10061—Polarization control
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
    • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
    • H01S3/14—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range characterised by the material used as the active medium
    • H01S3/16—Solid materials
    • H01S3/163—Solid materials characterised by a crystal matrix
    • H01S3/1671—Solid materials characterised by a crystal matrix vanadate, niobate, tantalate
    • H01S3/1673—YVO4 [YVO]

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Abstract

The invention relates to a Laguerre Gaussian beam generating device and method, and belongs to the field of lasers. The laser polarization beam splitter comprises a pumping laser, a collimating lens, a focusing lens, a concave dichroic mirror, a concave reflecting mirror highly reflecting laser, a plane laser reflecting mirror, a polarizing plate, an 1/4 wave plate, a laser crystal and a polarization beam splitter; the laser crystal is a uniaxial crystal, the laser crystal is used as a gain medium to generate laser, the spin angular momentum of partial circularly polarized light is converted into orbital angular momentum, the 1/4 wave plate is used for converting the polarization state of the light between circularly polarized light and linearly polarized light, and the polarization beam splitter mirror is used for outputting vortex rotation with the topological kernel number of 2; the partial laser passes through another 1/4 wave plate and a polarization beam splitter, and the output forms vortex laser. Another portion of the laser continues to oscillate within the laser cavity providing energy for conversion to eddy rotation. The vortex laser has no interference of other modes, has high power and high efficiency, is not limited by wavelength, and can generate high-purity vortex laser.

Description

Laguerre Gaussian beam generation device and method
Technical Field
The invention relates to a Laguerre Gaussian beam generating device and method, and belongs to the field of laser.
Background
The generation and application of the laguerre gaussian beam are one of the research hotspots in the world in recent years, the wavefront of the light beam is spiral, and a phase singularity exists in the center of the light beam, so that the central light intensity of the laguerre gaussian beam is 0, and the laguerre gaussian beam is also called an OAM (orbital angular momentum) light beam because the laguerre gaussian beam carries orbital angular momentum. The Laguerre Gaussian beam plays an important role in various fields, can realize non-contact capture of particles in the biological field, can directly measure the angular velocity of a rotating body in the measurement field, and can realize a new information coding mode in the optical communication field.
At present, the modes of directly generating the Laguerre Gaussian beam in the cavity comprise an extra-cavity method and an intra-cavity direct generation method. The mode of the external cavity conversion method is simple, but is easily influenced by an optical device, so that the conversion efficiency, the power and the purity of the Laguerre Gaussian beam are low;
the mode generation in cavity is to use laser crystal to generate Laguerre Gauss beam in cavity directly, the mode mainly includes the method of inserting phase element into resonant cavity directly and the non-planar rotating light path technology, the former is limited by inserted optical device, the latter is only for single wavelength and has low damage threshold. The first one is an annular pumping method, which modulates the light spot of the pump light into an annular shape, realizes the direct oscillation output of the vortex laser through the mode matching of the pump light and the oscillation laser, inevitably causes the complexity of the whole laser device in the modulation process of the pump light, and makes the ring of the pump light too troublesome and has poor mode control, for example, the mode matching is carried out through the annular pump light spot, and the problem that the pump light leaked from the laser cavity cannot be recycled is serious. The second is ring doping, which changes the conventional fiber core doping into a ring doping layer, such as a ring doping layer-based optical fiber and a laser including the same proposed by the university of science and technology in china, although laser oscillation is actually performed in a ring waveguide, the position arrangement and refractive index control of each cladding are still cumbersome. The third method is to recover the pump light leaked from the laser cavity, such as the ring pump laser proposed by the institute of optoelectronics of the chinese academy of sciences, although the pump light recovery device is attached, the requirements for the size and placement position of the pump focusing mirror are high, the efficiency is still not high enough, and the pump laser is susceptible to other modes.
Disclosure of Invention
Aiming at the defects of the prior art, the Laguerre Gaussian beam generating device and method for converting the spin angular momentum into the orbit angular momentum based on the intracavity direct oscillation method by using the uniaxial laser crystal as the gain medium are provided, the structure is simple, the use is convenient, and the laser is continuously converted between the linear polarized light and the circular polarized light.
In order to achieve the technical purpose, the laguerre gaussian beam generating device comprises a pump laser a, a collimating lens a, a focusing lens a, a concave dichroic mirror a and a concave reflecting mirror a which are arranged on a horizontal axis, wherein a laser crystal a is arranged between the concave dichroic mirror a and the concave reflecting mirror a, and the concave surfaces of the concave dichroic mirror a and the concave reflecting mirror a and the laser crystal a horizontally form an inclination angle of 3-10 degrees; a resonant cavity is arranged on the ray path of the concave dichroic mirror a, the resonant cavity comprises 1/4 wave plates b, a polarizing film and a plane mirror b which are sequentially arranged, and a 1/4 wave plate a, a polarization beam splitter mirror a and a plane mirror a are sequentially arranged on the pipeline path of the concave mirror a; the laser crystal a is excited by pump laser generated by a pump laser device a to generate laser with the wavelength of 790nm-808nm through resonant cavity oscillation, so that circularly polarized light and linearly polarized light are converted ceaselessly, then a polarization beam splitter mirror a is used for screening to enable the circularly polarized light and the linearly polarized light to become vortex-generated optical rotation periodically, and the laser which is emitted into the laser crystal a is levorotatory circularly polarized laser under the screening of a vertical polarizing film.
The focusing lens a is a plano-convex lens with two surfaces plated with high-transmittance films corresponding to the central wavelength of the pump light and a focal length of 7.5cm and a transmittance of more than 95%, and the collimating lens a is a plano-convex lens with two surfaces plated with high-transmittance films corresponding to the central wavelength of the pump light and a focal length of 15cm and a transmittance of more than 95%; the front of the concave dichroic mirror a facing the pumping source is plated with a film highly transmitting the pumping light, and the back is plated with a film highly reflecting the laser.
The laser crystal a can generate laser and is a uniaxial crystal, crystals including a tetragonal system, a trigonal system and a hexagonal system are all optical uniaxial crystals, and the uniaxial laser crystal is used as a gain medium, so that the spin angular momentum is converted into the orbital angular momentum; the doping ion of the laser crystal a is Nd3+、Yb3+、Er3+、Tm3+、Ho3+One of the rare earth ions is plated with antireflection films corresponding to the central wavelength of the pump light and the central wavelength of the laser light on the left end face and the right end face; the laser crystal a is Nd, YVO4, and the left and right end faces are both plated with antireflection films with transmittance greater than 95% corresponding to the central wavelength of the pump light and the central wavelength of the laser light.
The pump laser a is a semiconductor laser or a fiber laser with the generation wavelength of 800nm, and the central wavelength of the pump laser a is lambda0800nm, the tail fiber core diameter of the fiber laser is 100um, and the numerical aperture NA of the semiconductor laser is 0.22.
A working method of a Laguerre Gaussian beam generating device comprises the following steps: the pump laser emitted by a pump laser a is collimated through a collimating lens a, then the pump laser is focused through a focusing lens a, the focused pump laser enters a laser crystal a through a concave dichroic mirror a, the pump laser entering the laser crystal a enables the laser crystal a to generate laser which is emitted to a concave reflecting mirror a, the generated laser comprises two parts, one part is levorotatory circularly polarized light, the other part is a dextrorotatory vortex rotation with the topological kernel number of 2, after being reflected to 1/4 wave plate a through a left concave reflecting mirror a, the levorotatory circularly polarized light of the laser injected into 1/4 wave plate a is converted into a vertically polarized linearly polarized light, and the dextrorotatory vortex rotation is converted into a horizontally polarized vortex light; vortex light polarized in the horizontal direction and linearly polarized light polarized in the vertical direction pass through a polarization beam splitter mirror and are completely divided into two beams of light, the vortex light is separated by the polarization beam splitter mirror a and then output, the vertically polarized light beam continues to and fro through a plane reflector mirror a and is converted into relatively right circularly polarized light through an 1/4 wave plate a, the circularly polarized light is reflected by a concave reflector mirror a and then enters a laser crystal a again to generate the same right circularly polarized light and left circularly polarized light, a pump laser beam which is generated by a collimating lens a and a focusing lens a along with the pump laser a is converted into linearly polarized light polarized in the vertical direction and horizontally polarized circularly polarized light through a 1/4 wave plate b of a resonant cavity respectively, then the two parts of light are eliminated after continuously passing through a polarizing plate, the horizontally polarized vortex light is left, and the linearly polarized light in the vertical direction is reflected to a concave dichroic mirror a by the plane reflector mirror b, after being reflected by the concave dichroic mirror a4, the light is still linearly polarized in the vertical direction, and the previous steps are continuously repeated.
A Laguerre Gaussian beam generating device comprises a pump laser b, a collimating lens b, a focusing lens, a concave dichroic mirror b, a laser crystal b and a concave reflecting mirror b which are arranged on a horizontal axis, wherein the horizontal angles between the concave dichroic mirror b and the laser crystal b are 3-10 degrees, a linear polarizer and a plane reflecting mirror d which are arranged on the same axis and have an included angle of 5 degrees in the horizontal direction are sequentially arranged on a reflecting light path of the concave dichroic mirror b, 1/4 wave plates c and concave reflecting mirrors c are sequentially arranged on the reflecting light path of the concave reflecting mirror b, 1/4 wave plates c and concave reflecting mirrors c are inclined at an angle of 5 degrees with the incident direction of pump light, a polarized light crystal and a concave reflecting mirror d are sequentially arranged on a reflecting pipeline of the concave reflecting mirror c, 1/4 wave plates d which are arranged on the same axis and have an included angle of 5 degrees with the horizontal direction are sequentially arranged on the reflecting light path of the concave reflecting mirror d, a polarizing beam splitter mirror b, and a plane mirror c.
A light beam generating method of a Laguerre Gaussian light beam generating device comprises the following steps:
after the pump laser b generates pump light, the pump light can be output by the optical fiber coupling unit, and then the pump light is collimated and focused by the collimating lens b and the focusing lens b in sequence;
after collimation and focusing are finished, pumping light is sent to the laser crystal b through the concave dichroic mirror b in sequence and generates up-conversion fluorescence under the excitation of the pumping light, the up-conversion fluorescence is reflected to the polarizing plate through the concave dichroic mirror b, under the selection of the polarizing plate, the central wavelength of the laser passing through the laser crystal b is 1532nm, the laser passes through the plane reflecting mirror d and is reflected to the concave dichroic mirror b, the laser passes through the concave dichroic mirror b and enters the laser crystal b, and at the moment, the laser of the laser crystal b only contains the laser polarized in the vertical direction;
the laser polarized in the vertical direction of the laser crystal b is reflected by the concave reflecting mirror b and enters the 1/4 wave plate c to generate left-handed circularly polarized light, and the laser generated after the circularly polarized light enters the polarized light crystal comprises two parts, wherein one part is the same left-handed circularly polarized light, and the other part is the right-handed vortex rotation with the topological nucleus number of 2;
two parts of laser generated by two crystals with different polarized lights are reflected by a left concave mirror d and then enter 1/4 wave plates d, wherein, left-handed circularly polarized light is converted into linearly polarized light with vertical direction polarization, and right-handed vortex optical rotation is converted into vortex light with horizontal direction polarization;
vortex light polarized in the horizontal direction and linearly polarized light polarized in the vertical direction are completely divided into vortex light beams and vertically polarized light beams after passing through a polarization beam splitter mirror b, the vortex light beams are output after being separated by the polarization beam splitter mirror b, the vertically polarized light beams continue to reciprocate after being reflected by a sending plane reflector, are converted into circularly polarized light which is viewed rightwards in a reverse direction through an 1/4 wave plate d, and are reflected by a concave surface reflector d and then enter a single-axis crystal again to generate circularly polarized light which is viewed rightwards in the reverse direction and vortex rotation which is viewed leftwards in the same direction;
after the same right-handed circularly polarized light and the same left-handed vortex light are reflected by the concave reflecting mirror c in a reverse view, the same right-handed circularly polarized light and the same left-handed vortex light are respectively converted into linearly polarized light in the vertical direction and vortex light in the horizontal direction through the 1/4 wave plate c, after the linearly polarized light in the vertical direction and the vortex light in the horizontal direction continue to generate laser through the laser crystal b, the horizontally polarized vortex light is eliminated through the polarizing plate, the linearly polarized light in the vertical direction is remained, the linearly polarized light in the vertical direction is still reflected by the concave dichroic mirror b, and the previous steps are continuously repeated.
The pump laser b is a semiconductor laser for generating pump light with wavelength of 1532nm and central wavelength of λ0The core diameter of the optical fiber is 1532nm and the NA is 0.1 um.
The focusing lens is a plano-convex lens with two sides plated with 1532nm high-transmittance films and a focal length of 2.5cm, and the collimating lens b is a plano-convex lens with two sides plated with 1532nm high-transmittance films and a focal length of 10 cm.
Has the advantages that: the polarization plate and the 1/4 wave plate are arranged, so that the pump laser continuously converts circularly polarized light and linearly polarized light, and the vertical polarization plate is used for screening to form a resonant cavity capable of periodically generating vortex rotation. The method realizes the generation of the Laguerre Gaussian beam with higher purity by the intracavity direct oscillation method, and solves the problems of difficult manufacturing process, high manufacturing cost, difficult generation of the beam and the like of an optical device when the Laguerre Gaussian beam is generated. The vortex laser has the advantages of simple structure, low implementation cost, no interference of other modes, high power and efficiency, no limitation of wavelength and capability of generating high-purity vortex laser.
Drawings
FIG. 1 is a schematic structural diagram of an embodiment of a Laguerre Gaussian beam generating device according to the present invention;
FIG. 2 is a schematic diagram of the intensity distribution of right-handed vortex light in accordance with the present invention;
FIG. 3 is a schematic diagram showing the intensity distribution density of left-handed circularly polarized light in the present invention;
FIG. 4 is a schematic structural diagram of a Laguerre Gaussian beam generating device according to a second embodiment of the present invention;
in the figure: 1-pump laser a, 2-collimating lens a, 3-focusing lens a, 4-concave dichroic mirror a, 5-laser crystal a, 6-concave mirror a, 7-1/4 wave plate a, 8-polarizing beam splitter mirror a, 9-plane mirror a, 10-1/4 wave plate b, 11-polarizing plate, 12-plane mirror b, 13-pump laser b, 14-collimating lens b, 15-focusing lens b, 16-concave dichroic mirror b, 17-laser crystal b, 18-concave mirror b, 19-1/4 wave plate c, 20-concave mirror c, 21-polarizing crystal, 22-concave mirror d, 23-1/4 wave plate d, 24-polarizing beam splitter mirror b, 25-plane mirror c, 26-linear polarizer, 27-plane mirror d.
Detailed Description
Embodiments of the invention are further described below with reference to the accompanying drawings:
example 1: generating a Laguerre Gaussian beam by using a crystal;
as shown in fig. 1, a new laguerre gaussian beam generating apparatus is characterized in that it comprises the following steps:
the laser device comprises a pump laser a1, a collimating lens a2, a focusing lens a3, a concave dichroic mirror a4, a laser crystal a5, a concave reflecting mirror a6 and a polarization beam splitter mirror a8 which are sequentially arranged; the resonator includes a linearly polarizing plate 11 for generating linearly polarized light, 1/4 wave plates c7 and 1/4 wave plate 10, a plane mirror c12, and a concave mirror a6 for reflecting laser light and changing the direction of the optical path.
The concave reflector a6 is obliquely arranged at an angle of 5 degrees with the incident direction of the pump light, one surface of the concave dichroic mirror a (4) facing the pump source is plated with a film highly transmitting the pump light, and the reverse surface is plated with a film highly reflecting the laser light.
The optical fiber coupling unit is used for coupling and outputting pump light generated by a pump source, and the pump laser is a semiconductor laser or an optical fiber laser which generates the wavelength of 800 nm.
The pump laser has a central wavelength of λ0800nm, the tail fiber core diameter of the semiconductor laser is 100um, and the numerical aperture NA of the semiconductor laser is 0.22.
The collimating lens is used for collimating the pump light, and the focusing lens is used for focusing the pump light. The concave reflector is a concave reflector. The focusing lens is a plano-convex lens with two surfaces plated with high-transmittance films of 800nm and transmittance of more than 95% and a focal length of 7.5cm, and the collimating lens is a plano-convex lens with two surfaces plated with high-transmittance films of 800nm and transmittance of more than 95% and a focal length of 15 cm; the reflecting lens is plated with a film which is highly reflective to the pump light. The laser crystal is Nd, YVO4 with the doping concentration of 1.22 at.%, and the left end face and the right end face are both plated with antireflection films with the transmittances of more than 95% for 800nm and 1064 nm;
the new laguerre gaussian beam generation apparatus is further illustrated by the examples: firstly, a pump laser a1, a collimating lens a2, a focusing lens a3, a concave dichroic mirror a4, a laser crystal a5 and a concave reflecting mirror a6 are arranged on a horizontal axis; 1/4 wave plate 7, polarization beam splitter a8 and plane mirror 9 are arranged on the same axis, and the included angle between the plane mirror and the horizontal direction is 5 degrees; 1/4 wave plate 10, vertical polarizer 11, and plane mirror 12 are arranged on the same axis, and the angle with the horizontal direction is also 5 °. The pump laser a1 can be selected from semiconductor laser for generating pump light with wavelength of 800nm, preferably, the pump laser a1 is adopted with central wavelength of lambda0A semiconductor laser with 800nm optical fiber core diameter of 100um and NA of 0.22;
after the pump light is generated, the pump light can be output through the optical fiber coupling unit, and then the pump light is collimated and focused respectively through the collimating lens a2 and the focusing lens a3 in sequence, in order to enable the collimating and focusing effects to be better, the focusing lens a3 is a plano-convex mirror with two surfaces coated with a high-transmittance film with the transmittance of 800nm and more than 95% and the focal length of 7.5cm, and the collimating lens a2 is a plano-convex mirror with two surfaces coated with a high-transmittance film with the transmittance of 800nm and more than 95% and the focal length of 15 cm;
after collimation and focusing are finished, the pump light passes through the concave dichroic mirror a4, the laser crystal a5 is excited by the pump light to generate laser with the wavelength of 790nm-808nm through a resonant cavity in an oscillating way, the laser which is emitted into the laser crystal a5 is left-handed circularly polarized laser under screening of the vertical polarizing plate 11, furthermore, the laser which is emitted into the crystal comprises two parts, one part is the same left-handed circularly polarized light as shown in fig. 3, while the other part is right-handed vortex optical rotation with the topological nucleus number of 2, the laser is emitted into the 1/4 wave plate 7 after being reflected by the left concave reflecting mirror a6, further, the left-handed circularly polarized light is converted into vertically polarized linearly polarized light, the right-handed vortex optical rotation is converted into horizontally polarized vortex optical rotation, and the right-handed vortex optical rotation is shown in fig. 2;
vortex light polarized in the horizontal direction and linearly polarized light polarized in the vertical direction are completely divided into two beams of light after passing through a polarization beam splitter mirror 7, the vortex light is output, the vertically polarized light beam is reflected by a plane reflector 8 and then continuously returns, is converted into right-handed circularly polarized light after passing through an 1/4 wave plate 7, is reflected by a concave reflector a6, and is reflected into a laser crystal a5 again to generate the same right-handed circularly polarized light and left-handed vortex rotation in the opposite direction;
further, after being reflected by the concave dichroic mirror a4, the two portions of light are respectively converted into linearly polarized light in the vertical direction and vortex polarized light in the horizontal direction through the 1/4 wave plate 10, after passing through the polarizing plate 11, the horizontally polarized vortex light is eliminated, the linearly polarized light in the vertical direction is left, after being reflected by the concave dichroic mirror a4, the linearly polarized light in the vertical direction is still obtained, and the previous steps are continuously repeated.
The optical fiber coupling unit is used for coupling and outputting pump light generated by a pump source, and the pump laser is a semiconductor laser or an optical fiber laser which generates a semiconductor laser or an optical fiber laser with the central wavelength corresponding to the absorption peak of the crystal. The crystal must satisfy not only the laser light generation but also the uniaxial crystal. Crystals of tetragonal system, trigonal system and hexagonal system are all optical uniaxial crystals, and a uniaxial laser crystal is used as a gain medium, so that the spin angular momentum is converted to the orbital angular momentum. The formula used in principle is as follows:
Figure BDA0003560260960000061
wherein:
Figure BDA0003560260960000062
Figure BDA0003560260960000063
where λ is the wavelength, w0Is the beam radius, n0And neThe refractive indexes of the o light and the e light of the crystal are shown.
Wherein E is an electric field constant, Ein is an input electric field, and Eout is an output electric field;
example 2: generation of a laguerre beam using two crystals
The invention is further described below with reference to the accompanying drawings.
As shown in fig. 4, a cavity type is generated for the second laguerre gaussian beam, the apparatus comprising the steps of:
the laser comprises a pump laser a13, a collimating lens 14, a focusing lens 15, a concave dichroic mirror 16, a laser crystal b17, a concave reflecting mirror b18, a polarization beam splitter mirror b24, a linear polarizer 26, a 1/4 wave plate c19, a 1/4 wave plate d23, a plane reflecting mirror c25, a plane reflecting mirror d27, a polarized light crystal 21, a concave reflecting mirror c20 and a concave reflecting mirror d22 in sequence.
The concave reflector b18 is obliquely arranged at an angle of 5 degrees with the incident direction of the pump light, one surface of the concave dichroic mirror a (4) facing the pump source is plated with a film highly transmitting the pump light, and the reverse surface is plated with a film highly reflecting the laser light.
The optical fiber coupling unit is used for coupling out pump light generated by a pump source, and the pump laser is a semiconductor laser or an optical fiber laser which generates light with the wavelength of 1532 nm.
The pump laser has a central wavelength of λ01532nm, the tail fiber core diameter of the semiconductor laser is 200um, and the numerical aperture of the semiconductor laser is NA 0.1.
The collimating lens is used for collimating the pump light, and the focusing lens is used for focusing the pump light. The concave reflector is a concave reflector. The focusing lens is a plano-convex lens with two surfaces plated with high-transmittance films of 1532nm and transmittance greater than 95% and a focal length of 2.5cm, and the collimating lens is a plano-convex lens with two surfaces plated with high-transmittance films of 1532nm and transmittance greater than 95% and a focal length of 10 cm; the reflecting lens is plated with a film which is highly reflective to the pump light. The laser crystal is doped with Er with the concentration of 0.5 at.%: YAG, and the end faces are plated with anti-reflection films with the transmittance of more than 95% for 1532nm and 1064 nm;
the new laguerre gaussian beam generation apparatus is further illustrated by the examples: firstly, a pump laser a13, a collimating lens 14, a focusing lens 15, a concave dichroic mirror 16, a laser crystal 17 and a concave reflecting mirror b18 are arranged on a horizontal axis; 1/4 wave plate c19 and concave reflector c20 incline at 5 degrees with the incident direction of the pump light, and the polarization beam splitter mirror b24, the plane reflector 25 and the 1/4 wave plate d23 are arranged on the same axis and form an angle of 5 degrees with the horizontal direction; the concave mirror c20, the concave mirror d22, and the uniaxial crystal 21 are arranged on the same axis, and the polarizing plate 26 and the plane mirror 27 are arranged on the same axis, and the angle with the horizontal direction is also 5 °. The pump laser a13 can be selected from semiconductor laser for generating pump light with wavelength of 1532nm, and preferably the pump laser a13 is adopted with central wavelength of λ0A 1532nm semiconductor laser with 200um optical fiber core diameter and 0.1 NA;
after pump light is generated, the pump light can be coupled out through the optical fiber coupling unit, then the pump light is collimated and focused through the collimating lens 14 and the focusing lens 15 in sequence, and in order to achieve better collimating and focusing effects, the focusing lens 15 is a plano-convex lens with two surfaces plated with 1532nm high-transmittance films and a focal length of 2.5cm, and the collimating lens 14 is a plano-convex lens with two surfaces plated with 1532nm high-transmittance films and a focal length of 10 cm;
after the collimation and the focusing are finished, the pump light passes through the concave dichroic mirror 16, the laser crystal 17 generates up-conversion fluorescence under the excitation of the pump light, and generates laser with a center wavelength of 1532nm by the oscillation of the resonant cavity, and further, with the selection of the polarizing plate 26, the laser light incident on the laser crystal 17 contains only vertically polarized laser light, further, the incident 1/4 wave plate c19 generates left-handed circularly polarized light, and further, the laser light generated after the left-handed circularly polarized light is incident on the uniaxial crystal 21 contains two parts, one of which is the same left-handed circularly polarized light, and the other part is the vortex rotation with the topological kernel number of 2 of right-handed rotation, and after the vortex rotation is reflected by the left concave mirror d22, the light enters 1/4 wave plate d23, the left-handed circularly polarized light is converted into linearly polarized light polarized in the vertical direction, and the right-handed vortex rotation is converted into vortex light polarized in the horizontal direction;
the vortex light polarized in the horizontal direction and the linearly polarized light polarized in the vertical direction are completely divided into two beams of light after passing through the polarization beam splitter b24, the vortex light is output, the vertically polarized light beam continues to reciprocate after being reflected by the plane reflector 25, is converted into the circularly polarized light which is viewed rightwards in the reverse direction through the 1/4 wave plate d23, is reflected by the concave reflector d22, and is incident into the uniaxial crystal 21 again to generate the circularly polarized light which is viewed rightwards in the reverse direction and the vortex rotation which is viewed leftwards in the reverse direction;
after being reflected by the concave reflector c20, the two parts of light are respectively converted into linearly polarized light in the vertical direction and vortex light polarized in the horizontal direction through the 1/4 wave plate c19, after the two parts of light continuously generate laser through the crystal 17, the vortex light polarized in the horizontal direction is eliminated through the polaroid 26, the linearly polarized light in the vertical direction is remained, after being reflected by the concave dichroic mirror 16, the linearly polarized light in the vertical direction is still obtained, and the previous steps are continuously repeated.

Claims (9)

1. A Laguerre Gaussian beam generating device is characterized in that: the laser device comprises a pump laser a (1), a collimating lens a (2), a focusing lens a (3), a concave dichroic mirror a (4) and a concave reflecting mirror a (6) which are arranged on a horizontal axis, wherein a laser crystal a (5) is arranged between the concave dichroic mirror a (4) and the concave reflecting mirror a (6), and the concave surfaces of the concave dichroic mirror a (4) and the concave reflecting mirror a (6) and the laser crystal a (5) form an inclination angle of 3-10 degrees horizontally; a resonant cavity is arranged on the light path of the concave dichroic mirror a (4), the resonant cavity comprises 1/4 wave plate b (10), a polarizing plate (11) and a plane mirror b (12) which are sequentially arranged, and a 1/4 wave plate a (7), a polarization beam splitter mirror a (8) and a plane mirror a (9) are sequentially arranged on the pipeline path of the concave mirror a (6); the laser crystal a (5) is excited by pump laser generated by a pump laser a (1) to generate laser with the wavelength of 790nm-808nm through resonant cavity oscillation, so that circularly polarized light and linearly polarized light are converted continuously, then a polarization beam splitter a (8) is used for screening to enable the circularly polarized light and the linearly polarized light to become vortex-generated optical rotation periodically, and the laser entering the laser crystal a (5) is levorotatory circularly polarized laser under the screening of a vertical polarizing plate (11).
2. The apparatus for generating a laguerre gaussian beam according to claim 1, wherein: the focusing lens a (3) is a plano-convex lens with two surfaces plated with high-transmittance films corresponding to the central wavelength of the pump light and a focal length of 7.5cm and a transmittance of more than 95%, and the collimating lens a (2) is a plano-convex lens with two surfaces plated with high-transmittance films corresponding to the central wavelength of the pump light and a focal length of 15cm and a transmittance of more than 95%; the front surface of the concave dichroic mirror a (4) facing the pumping source is plated with a film which is highly transparent to pumping light, and the back surface is plated with a film which is highly reflective to laser.
3. The laguerre gaussian beam generation apparatus according to claim 1, wherein: the laser crystal a (5) can generate laser and is a uniaxial crystal, crystals including a tetragonal system, a trigonal system and a hexagonal system are all optical uniaxial crystals, and the uniaxial laser crystal is used as a gain medium, so that the spin angular momentum is converted to the orbital angular momentum; the doping ion of the laser crystal a (5) is Nd3+、Yb3+、Er3+、Tm3+、Ho3+One of the rare earth ions is plated with antireflection films corresponding to the central wavelength of the pump light and the central wavelength of the laser light on the left end face and the right end face; the laser crystal a (5) is Nd, YVO4, and the left and right end faces are both plated with antireflection films with transmittance of more than 95% corresponding to the central wavelength of the pump light and the central wavelength of the laser light.
4. The laguerre gaussian beam generation apparatus according to claim 1, wherein: the pump laser a (1) is a semiconductor laser or a fiber laser which generates a laser with the wavelength of 800nm, and the central wavelength of the pump laser a (1) is lambda0800nm, the tail fiber core diameter of the fiber laser is 100um, and the numerical aperture NA of the semiconductor laser is 0.22.
5. A method of operating the laguerre gaussian beam generating apparatus of claim 1, comprising the steps of: the pump laser emitted by a pump laser a (1) is collimated by a collimating lens a (2), then the pump light is focused by a focusing lens a (3), the focused pump light enters a laser crystal a (5) through a concave dichroic mirror a (4), the pump laser entering the laser crystal a (5) enables the laser crystal a (5) to generate laser light to emit to a concave reflector a (6), the generated laser light comprises two parts, one part is left-handed circularly polarized light, the other part is right-handed vortex optical rotation with the topological kernel number of 2, after the generated laser light is reflected to 1/4 wave plate a (7) by a left concave reflector a (6), the left-handed circularly polarized light of the laser entering 1/4 wave plate a (7) is converted into linearly polarized light in the vertical direction, and the right-handed vortex optical rotation is converted into vortex light polarized in the horizontal direction; vortex light polarized in the horizontal direction and linearly polarized light polarized in the vertical direction are completely divided into two beams of light after passing through a polarization beam splitter mirror (7), the vortex light is separated by a polarization beam splitter mirror a (8) and then output, the vertically polarized light beam continues to reciprocate in the original path through a plane reflector a (9), the vertically polarized light beam is converted into circularly polarized light which is relatively right-handed through a 1/4 wave plate a (7), the circularly polarized light is reflected by a concave reflector a (6) and then enters a laser crystal a (5) again to generate vortex optical rotation which is the same as the circularly polarized light on the right hand and the vortex optical rotation on the left hand and is reversely seen, a pumping laser beam which is newly generated by a following pump laser a (1) through a collimating lens a (2) and a focusing lens a (3) is converted into linearly polarized light polarized in the vertical direction and vortex optical rotation polarized in the horizontal direction through a 1/4 wave plate b (10) of a resonant cavity respectively, and then the vortex optical rotation on the two parts of light continues to eliminate the vortex light polarized in the horizontal direction after passing through a polarizing plate (11), the linearly polarized light polarized in the vertical direction is left to be reflected to the concave dichroic mirror a (4) by the plane reflecting mirror b (12), and is still the linearly polarized light polarized in the vertical direction after being reflected by the concave dichroic mirror a4, and the previous steps are repeated.
6. A Laguerre Gaussian beam generating device is characterized in that: comprises a pump laser b (13), a collimating lens b (14), a focusing lens (15), a concave dichroic mirror b (16), a laser crystal b (17) and a concave reflecting mirror b (18) which are arranged on a horizontal axis, wherein the concave dichroic mirror b (16), the concave reflecting mirror b (18) and the laser crystal b (17) are horizontally inclined at an angle of 3-10 degrees, a linear polarizer (26) and a plane reflecting mirror d (27) which are arranged on the same axis and have an included angle of 5 degrees in the horizontal direction are sequentially arranged on a reflecting light path of the concave dichroic mirror b (16), 1/4 wave plate c (19) and a concave reflecting mirror c (20) are sequentially arranged on the reflecting light path of the concave reflecting mirror b (18), the 1/4 wave plate c (19) and the concave reflecting mirror c (20) are inclined at an angle of 5 degrees with the incident direction of pump light, a polarizing crystal (21) and a concave reflecting mirror d (22) are sequentially arranged on the reflecting light path of the concave reflecting mirror c (20), 1/4 wave plate d (23), polarization beam splitter mirror b (24) and plane reflector c (25) which are arranged on the same axis and have an included angle of 5 degrees with the horizontal direction are sequentially arranged on the reflection light path of the concave reflector d (22).
7. A light beam generating method using the laguerre gaussian light beam generating apparatus of claim 6, comprising the steps of:
after the pump laser b (13) generates pump light, the pump light can be coupled out through the optical fiber coupling unit, and then the pump light is respectively collimated and focused through the collimating lens b (14) and the focusing lens b (15) in sequence;
after collimation and focusing are finished, pumping light is sent to a laser crystal b (17) through a concave surface dichroic mirror b (16) in sequence and generates up-conversion fluorescence under the excitation of the pumping light, the up-conversion fluorescence is reflected to a polarizing plate (26) through the concave surface dichroic mirror b (16), under the selection of the polarizing plate (26), the central wavelength of the laser passing through the laser crystal b (17) is 1532nm, the laser is reflected to the concave surface dichroic mirror b (16) through a plane reflecting mirror d (27), the laser enters the laser crystal b (17) after being reflected by the concave surface dichroic mirror b (16), and at the moment, the laser of the laser crystal b (17) only contains the laser polarized in the vertical direction;
the laser polarized in the vertical direction of the laser crystal b (17) is reflected by a concave reflector b (18) and enters 1/4 wave plate c (19) to generate left-handed circularly polarized light, and the laser generated after the circular circularly polarized light enters a polarized light crystal (21) comprises two parts, wherein one part is the same left-handed circularly polarized light, and the other part is right-handed vortex rotation with the topological nucleus number of 2;
two parts of laser generated by crystals (21) of two different polarized lights are reflected by a left concave reflecting mirror d (22) and then enter 1/4 wave plate d (23), wherein, left-handed circularly polarized light is converted into linearly polarized light polarized in the vertical direction, and right-handed vortex optical rotation is converted into vortex light polarized in the horizontal direction;
vortex light polarized in the horizontal direction and linearly polarized light polarized in the vertical direction are completely divided into vortex light beams and vertically polarized light beams after passing through a polarization beam splitter mirror b (24), the vortex light beams are separated by the polarization beam splitter mirror b (24) and then output, the vertically polarized light beams continue to reciprocate after being reflected by a sending plane reflector (25), are converted into circularly polarized light which is viewed rightwards in the reverse direction through an 1/4 wave plate d (23), and are reflected by a concave surface reflector d (22) and then enter a uniaxial crystal (21) again to generate circularly polarized light which is viewed rightwards in the reverse direction and vortex optical rotation which is viewed leftwards in the reverse direction;
after the same right-handed circularly polarized light and the same left-handed vortex light are reflected by the concave reflecting mirror c (20) in the opposite view, the same right-handed circularly polarized light and the same left-handed vortex light are respectively converted into linearly polarized light in the vertical direction and vortex light in the horizontal direction through the 1/4 wave plate c (19), after the linearly polarized light in the vertical direction and the vortex light in the horizontal direction continuously generate laser through the laser crystal b (17), the linearly polarized light in the horizontal direction is eliminated through the polarizing plate (26), the linearly polarized light in the vertical direction is remained, the linearly polarized light in the vertical direction is still obtained after the linearly polarized light in the vertical direction is reflected by the concave dichroic mirror b (16), and the previous steps are continuously repeated.
8. The method for generating a light beam by using a laguerre gaussian light beam generating apparatus according to claim 7, wherein: the pump laser b (13) is a semiconductor laser for generating pump light with wavelength of 1532nm and center wavelength of λ0The core diameter of the optical fiber is 1532nm and the NA is 0.1 um.
9. The beam generating method of the laguerre gaussian beam generating apparatus as claimed in claim 7, wherein: the focusing lens (15) is a plano-convex lens with two sides coated with 1532nm high-transmittance films and a focal length of 2.5cm, and the collimating lens b (14) is a plano-convex lens with two sides coated with 1532nm high-transmittance films and a focal length of 10 cm.
CN202210291199.2A 2022-03-23 2022-03-23 Laguerre Gaussian beam generating device and method Pending CN114784606A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117047307A (en) * 2023-08-31 2023-11-14 广东宏石激光技术股份有限公司 Dynamic light spot cutting adjusting device and cutting method based on vortex light beams

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117047307A (en) * 2023-08-31 2023-11-14 广东宏石激光技术股份有限公司 Dynamic light spot cutting adjusting device and cutting method based on vortex light beams
CN117047307B (en) * 2023-08-31 2024-05-24 广东宏石激光技术股份有限公司 Dynamic light spot cutting adjusting device and cutting method based on vortex light beams

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