CN112540457B - Vortex light beam generation device, system and method with adjustable topological number - Google Patents
Vortex light beam generation device, system and method with adjustable topological number Download PDFInfo
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- CN112540457B CN112540457B CN202011436316.7A CN202011436316A CN112540457B CN 112540457 B CN112540457 B CN 112540457B CN 202011436316 A CN202011436316 A CN 202011436316A CN 112540457 B CN112540457 B CN 112540457B
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Abstract
The invention discloses a vortex light beam generating device, a system and a method with adjustable topological number2and-A θ2Two spiral phase mirrors are sequentially arranged on the light path, and the angle difference of the two spiral phase mirrors is increased
The topological number of the resulting vortex beam is increased by 1. After the laser beam is positioned in the device, a spiral phase factor can be added to realize phase modulation, so that the energy distribution of the laser beam is changed into annular distribution, and the topological number of the obtained vortex beam is adjusted by rotating one or two spiral phase mirrors to control the angle difference of the two spiral phase mirrors, thereby realizing the annular light spot with adjustable size. According to the invention, a group of spiral phase mirrors with second-order nonlinear spiral structures are designed and superposed to generate vortex beams with adjustable topological numbers, so that annular light spots with energy distribution concentrated on the edge, larger diameter, longer focal depth and adjustable size are formed.
Description
Technical Field
The invention belongs to the field of laser application, and particularly relates to a vortex light beam generating device, a system and a method with adjustable topological numbers.
Background
The general gaussian beam energy distribution decreases from the center to the edge, with most of the energy concentrated in the center region. In the field of laser processing, particularly in the fields of laser welding, cutting, cladding and the like, ablation and other phenomena may occur due to overhigh central energy, and due to insufficient energy of the edge, the deeper the processing depth is, the more insufficient the energy of the edge is, so that the cutting section is not flat, and the processing quality, the processing precision and the like are obviously limited.
In order to solve the above problems, a commonly used processing method at present is to change a gaussian-distributed light spot into an annular light spot, the most typical annular light is vortex rotation, and the radius of the vortex rotation increases with the increase of the topological number, so that the spot size can be adjusted by adjusting the topological number of the vortex rotation for flexible processing, and the vortex rotation has polarization characteristics in various directions, so that the influence of the polarization direction of light on the action of laser and a substance can be ignored during processing. Compared with the light spots distributed in the common Gaussian mode, the energy of the annular light spots is concentrated on the edge ring band, the energy distribution is more uniform, the problem that the section is not flat due to insufficient edge energy when a thick laser plate is cut and the problems that the section is not flat, the splashing is excessive and the like when laser cutting, welding and cladding are carried out can be effectively avoided, and the yield of laser processing products is remarkably improved.
In the prior art, the main methods for outputting the annular light spot include the following methods: 1. vortex phase plate superposition is used for generating vortex rotation with adjustable topological charge number, each phase plate generates vortex rotation with fixed topological number, and the topological number of the vortex rotation generated by different phase plate superposition is the sum of the topological numbers of the used phase plates. Because the phase plate is expensive, more phase plates are needed to realize the flexible and adjustable vortex optical rotation topological number, and the method has high cost and is not flexible enough. 2. The combined annular light spot is generated based on the axicon, but due to the limitation of the material and the processing technology of the axicon, the range of the taper which can be processed and realized at present is limited, a larger error can be generated when the taper is too small, and the processing difficulty of the mirror surface formed by combining various conical surfaces with different tapers is very large for a crystal material, so that the adjustable range of the annular light spot output by adopting the transmission type axicon is relatively small on parameters such as the radius of the ring and the like, and the difficulty of outputting a plurality of annular combined light spots is larger, so that different processing requirements cannot be flexibly met, and in addition, the material of the axicon also influences the size of the bearable light power; 3. the method is characterized in that a combined annular light spot is generated based on a computer generated hologram method, any light spot containing the combined annular light spot can be designed and generated in principle, but the computer generated hologram method is completed by a spatial light modulator, the spatial light modulator generally uses off-axis first-order diffraction light, and factors such as loss and the like are added, so that the light energy utilization rate is low, and kilowatt-level laser cannot be borne, so that the use amount is relatively small; 4. the method has the advantages that the combined annular light spot is generated by adopting the laser with the adjustable light spot mode based on the optical fiber, the difficulty and the cost for realizing the adjustment of the light spot distribution mode in the optical fiber are high, and due to the fact that no adjustable external light path exists, the flexibility and the convenience in use are all deficient.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a vortex light beam generation device, a system and a method with adjustable topological number, wherein annular light spots with energy distribution concentrated at the edge, larger diameter and longer focal depth can be obtained by improving components of an optical system and the matching action mode among the components; and the rotation angle of the spiral phase mirror is further controlled and the phase change characteristic of the spiral phase mirror is set, so that the adjustment of the topological number of the vortex light beam and the adjustment of the change range of the spot size can be realized, and the laser processing device is suitable for various laser processing fields such as laser cutting and the like.
The technical scheme of the invention is realized as follows: the invention discloses a vortex light beam generating device with adjustable topological number, which comprises two spiral phase mirrors, wherein the phases of the two spiral phase mirrors are respectively set to be A theta2and-A θ2A is a constant and is used for controlling the change range of the topological number of the obtained vortex light beam, the obtained vortex optical rotation topological number is all integers from 0 to 4A pi, theta is an azimuth angle taking the circle center of the spiral phase mirror as an origin, the two spiral phase mirrors are sequentially arranged on the light path, the laser beam sequentially passes through the two spiral phase mirrors and is attached with a spiral phase factor with the set topological number to be changed into an annular vortex light beam, the topological number of the obtained vortex light beam is adjusted by rotating one or two spiral phase mirrors to control the angle difference of the two spiral phase mirrors, and the angle difference of the two spiral phase mirrors is
Integer multiples of.
Furthermore, the spiral phase mirror comprises two end faces, wherein one end face is a plane end face, the other end face is a step end face which takes the center as an origin and has a spiral shape with the height changing along with the azimuth, and the surface shape of the end face is only related to the refractive index of a material, the phase setting and the laser wavelength; and for any spiral phase mirror, the central axis of the spiral phase mirror is overlapped with the light beam of the collimation laser beam, the laser beam can be incident from the plane end face of the corresponding spiral phase mirror or can be incident from the step end face of the corresponding spiral phase mirror, and the light beam passes through the two spiral phase mirrors to carry out phase modulation.
Further, as the angular difference between the two helical phase mirrors increases
The topological number of the resulting vortex beam is increased by 1. The angular difference between the two helical phase mirrors must be
The obtained light beam is vortex-rotated only by integral multiple, and the topological number is the multiple.
Further, the central axes of the two helical phase mirrors are located on the same line. The distance between the two helical phase mirrors is set as required, and theoretically, the closer the distance between the two helical phase mirrors is, the better the distance between the two helical phase mirrors is.
Further, a first spiral phase mirror of the two spiral phase mirrors is connected with a first driving device, and the first spiral phase mirror is driven to rotate around the central axis of the first spiral phase mirror through the first driving device, or/and a second spiral phase mirror of the two spiral phase mirrors is connected with a second driving device, and the second spiral phase mirror is driven to rotate around the central axis of the second spiral phase mirror through the second driving device.
The central axis of the reflection type spiral phase mirror is coincided with the normal line of the center of the over-reflection type spiral phase mirror and is coincided with the optical axis.
The invention discloses a vortex light beam generation system with an adjustable topological number, which comprises a collimation unit, a focusing unit and a vortex light beam generation device, wherein the vortex light beam generation device is arranged on a light path between the collimation unit and the focusing unit;
the collimation unit is used for collimating the input laser to obtain a collimated laser beam;
the vortex beam generating device is used for adding spiral phase factors corresponding to the topological charge number to the collimated laser beams emitted by the collimating unit to form annular beams, and the topological charge number of the annular beams is determined by the angle difference of the two spiral phase mirrors;
the focusing unit is used for focusing the annular light beam emitted by the vortex light beam generating device to obtain light spots with annular energy distribution.
The vortex light beam generating system also comprises two scanning galvanometers, wherein the two scanning galvanometers are arranged on a light path between the vortex light beam generating device and the focusing unit, and the light path is switched through the two scanning galvanometers to change the focus position of a focusing surface.
Furthermore, a laser is arranged in front of the collimation unit, laser emitted by the laser is used as input laser of the collimation unit, and the laser emitted by the laser is laser with the light intensity in Gaussian distribution.
The invention also discloses a vortex light beam generation method with adjustable topological number, which comprises the following steps:
the laser emits laser with Gaussian light intensity, and the light beam is collimated by the collimating unit to obtain a collimated laser beam which is superposed with the central optical axes of the two spiral phase mirrors of the vortex light beam generating device;
the initial positions of two spiral phase mirrors of the vortex light beam generating device are aligned, at the moment, the vortex light beam generating device has no phase modulation effect on the passing laser beam, one of the spiral phase mirrors is rotated, and when the rotated angle is equal to
Integer multiple of N, i.e. the angular difference between the two helical phase mirrors is
Then, the vortex beam generating device adds a spiral phase factor exp (iNtheta) to the passing light beam, wherein i represents a complex symbol;
the focusing unit focuses the annular light beam emitted by the vortex light beam generating device, and the annular vortex light beam with the vortex topological number N is obtained on a focusing surface.
The invention has at least the following beneficial effects:
(1) the laser beam is collimated by the collimating unit, enters from one end of a first spiral phase mirror in the vortex beam generating device, is added with spiral phase factors with corresponding topological charge numbers to form an annular beam, and finally passes through the focusing unit to obtain an annular light spot with annular energy distribution. Under the same condition, the light beam is added with a spiral phase factor, and the focused annular light spot has the characteristics of larger radius, longer focal depth and high edge energy compared with the common focused light spot, so that the adverse effects of ablation and the like in laser processing can be effectively avoided, the material is heated more uniformly, and the processing quality is better;
(2) annular light spots are generated through the spiral phase mirror and can be regarded as pure phase modulation, the change of the amplitude can be ignored, the energy conversion rate is high, the loss is reduced, and the laser high-power processing device is suitable for laser high-power processing;
(3) the annular light spot generated by the spiral phase mirror has higher purity and stronger stability, and is not easily influenced by optical effects such as diffraction and the like;
(4) when the angle difference of the two spiral phase mirrors is a certain specific value, the spiral phase factor corresponding to the topological charge number is added to the phase of the light beam, so that the energy distribution of the laser beam is changed into annular distribution; the vortex light beam generating device can modulate the phase of the collimated laser beam through the action of the spiral phase mirror, so that the laser beam with the changed phase is emitted; according to the requirement of actual work, the rotation angle of the spiral phase mirror can be automatically adjusted, so that vortex rotation with different topological charge numbers can be obtained, the size of an annular focusing light spot can be changed, the size of the annular light spot can be continuously adjusted, and the cutting requirements of different plate thicknesses can be met;
(5) the system has good anti-maladjustment characteristic, and the change of the size of a light spot, the light beam offset and the focus offset can not influence the light field of annular energy distribution;
(6) when the method is used for laser additive manufacturing or laser surface treatment, the topological charge number of vortex rotation is changed, the adjustability of the width of a light spot is realized, the uniformity of the light field distribution is not influenced, and the action effect with consistent uniformity effect can be obtained.
In summary, with the optical system of the present invention, the laser beam is collimated into parallel light after passing through the collimating unit, then an annular beam is obtained through phase modulation, and finally the annular beam is focused into a high-energy annular spot through the focusing unit, which can be used in a plurality of fields such as laser cutting, marking, cladding, micro-machining, information processing, atomic manipulation, etc. The invention can generate the annular light spot with adjustable light spot size through the two spiral phase mirrors, has great significance in the laser processing technology, can further change the phase change characteristic of the spiral phase mirrors, realize the variable topological charge number of vortex rotation, further expand the topological charge number change range of vortex beams, can be flexibly adjusted according to the requirements of the user under different processing environments, can effectively solve the negative problems of uneven cutting section of a thick laser plate, ablation and the like caused by overhigh central energy and insufficient edge energy of the Gaussian beams at present, has adjustable light spot size, flexible use method and high energy utilization rate, and is suitable for high-power laser processing.
Drawings
FIG. 1 is a schematic diagram of a vortex beam generation system with adjustable topological number in embodiment 2 of the present invention;
FIG. 2 is a schematic diagram of the construction of the spiral phase mirror of the present invention;
FIG. 3 shows a vortex beam generating apparatus of embodiment 2 of the present invention in which a modulation constant A is 1 and a phase is set to θ2The phase diagram of the helical phase mirror of (1);
FIG. 4 is a schematic diagram of a collimated Gaussian beam of embodiment 2 of the present invention;
FIG. 5 is a focused light spot obtained by collimating the light beam only by the focusing unit in embodiment 2 of the present invention;
FIG. 6 shows the angle difference between two spiral phase mirrors in example 2 of the present invention
Generating a vortex rotation with a topological number of 1, and passing the vortex rotation through a focusing unit to form a light field distribution diagram at the position of a focusing surface, wherein (a) is a cross-section light field distribution diagram, and (b) is an axial-section light field distribution diagram;
FIG. 7 shows the angle difference between two spiral phase mirrors in example 2 of the present invention
Generating an axial section light field distribution diagram of the position of a focusing surface through a focusing unit, wherein the vortex rotation number is 3;
FIG. 8 is a schematic diagram of a vortex beam generation system with adjustable topological number in embodiment 3 of the present invention.
In the drawings: the device comprises a laser 1, a collimation unit 2, a first spiral phase lens 3, a second spiral phase lens 4, a focusing unit 5, a focusing surface 6, a first scanning galvanometer 7, a motor connected with the first scanning galvanometer 8, a second scanning galvanometer 9 and a motor connected with the second scanning galvanometer 10.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.
Example 1
Referring to fig. 1 and 2, the embodiment discloses a vortex light beam generation device with adjustable topological number, which comprises two spiral specific spiral phase mirrors, wherein the phases of the two spiral phase mirrors are respectively set to be a θ2and-A θ2A is constant and is used for controlling the change range of the topological number of the obtained vortex light beam, the obtained vortex optical rotation topological number is all integers from 0 to 4A pi, theta is an azimuth angle taking the circle center of the spiral phase mirror as the origin, the two spiral phase mirrors are sequentially arranged on the light path, the laser beam is emitted from the laser beam, and the laser beam is emitted from the laser beamThe annular vortex light beam is formed by attaching spiral phase factors with set topological numbers to the two spiral phase mirrors in sequence and then is changed into an annular vortex light beam, the topological numbers of the obtained vortex light beam are adjusted by rotating one or two spiral phase mirrors to control the angle difference between the two spiral phase mirrors, and the annular light spot with adjustable size is realized
I.e. the angular difference between the two helical phase mirrors increases
The topological number of the resulting vortex beam is increased by 1.
The invention utilizes two spiral phase mirrors to construct a vortex light beam generating device, referring to fig. 2, the spiral phase mirrors are consistent with the prior art and are transparent plates with fixed refractive indexes, each spiral phase mirror comprises two end faces, one of the end faces is of a plane structure, the other end face is a step face (similar to a rotary step) which takes a center as an origin and has a spiral shape, the height of the step face changes along with an azimuth angle, and the surface shape of the step face is only related to the refractive index of a material, the phase setting and the laser wavelength; the thickness increased by the steps of the spiral phase plate can be calculated by directly referring to the prior art according to the phase distribution and the material refractive index of the spiral phase mirror; the thickness of the spiral phase mirror is generally in the micron order and can be ignored, so the influence of the phase mirror on the light intensity can be ignored. And for any spiral phase mirror, the central axis of the spiral phase mirror is overlapped with the light beam of the collimation laser beam, the laser beam can be incident from the plane end face of the corresponding spiral phase mirror or can be incident from the step end face of the corresponding spiral phase mirror, and the light beam passes through the two spiral phase mirrors to carry out phase modulation. The spiral phase mirror specific to the spiral of the present invention is essentially a circular diffractive optical element.
The variable annular light spot optical system can further enlarge the variation range of the vortex optical topological number by setting the phase variation characteristic of the spiral phase mirror, such as increasing the constant A.
After the laser beam passes through the spiral phase plate, the phases of the emergent beams are correspondingly changed due to different optical paths of the laser beam passing through different azimuth angles. The angle difference between the spiral phase mirrors is rotated to be a certain fixed value, so that the emergent light beam is added with a spiral phase factor exp (il theta), wherein l is the topological charge of the spiral phase plate, the topological charge can be changed along with the angle difference between the two spiral phase mirrors, and i represents a complex number sign, and therefore the light beam becomes a circular vortex light beam with the adjustable topological number. The size of the annular light spot obtained by the optical system is influenced by the topological charge number, and the larger the topological charge number is, the larger the energy depression area of the obtained annular light spot is, and the larger the diameter of the light spot is.
Further, the helical phase mirror rotates by an angle of
Integral multiple of (i.e. the angular difference between the two helical phase mirrors must be)
The obtained light beam is vortex-rotated only by integral multiple, and the topological number is the multiple.
Further, the central axes of the two helical phase mirrors are located on the same line.
Further, a first spiral phase mirror of the two spiral phase mirrors is connected with a first driving device, and the first spiral phase mirror is driven to rotate around the central axis of the first spiral phase mirror through the first driving device, or/and a second spiral phase mirror of the two spiral phase mirrors is connected with a second driving device, and the second spiral phase mirror is driven to rotate around the central axis of the second spiral phase mirror through the second driving device.
The invention can fix one of the spiral phase mirrors and only control the other spiral phase mirror to rotate, and certainly, can also control the two spiral phase mirrors to rotate simultaneously.
According to the topological number of the required vortex light beams, the required angle difference of the two spiral phase mirrors is calculated, so that one or two spiral phase mirrors are controlled to rotate to reach the required angle difference. The invention can calculate the required angle difference of the two spiral phase mirrors through the controller according to the topological number of the required vortex light beam, and automatically drive one or two spiral phase mirrors to rotate to reach the required angle difference, so that the vortex optical rotation with the required topological charge number is obtained after the light beam is emitted from the vortex light beam generating device.
Example 2
Referring to fig. 1 to 7, the present embodiment discloses a vortex light beam generating system with an adjustable topological number, which includes a collimating unit 2, a focusing unit 5, and a vortex light beam generating device described in embodiment 1, where the vortex light beam generating device is disposed on an optical path between the collimating unit 2 and the focusing unit 5;
the collimation unit 2 is used for collimating the input laser to obtain a collimated laser beam;
the vortex beam generating device is used for adding spiral phase factors corresponding to the topological charge number to the collimated laser beams emitted by the collimating unit to form annular beams, and the topological charge number of the annular beams is determined by the angle difference of the two spiral phase mirrors;
the focusing unit 5 is used for focusing the annular light beam emitted by the vortex light beam generating device to obtain light spots with annular energy distribution.
Further, before the collimation unit, a laser 1 is further arranged, laser emitted by the laser 1 is used as input laser of the collimation unit, and the laser emitted by the laser 1 is laser with light intensity in gaussian distribution.
The vortex beam generating means is constituted by a first spiral phase mirror 3 and a second spiral phase mirror 4. The positions of the two spiral phase mirrors can be exchanged, namely the phase can be A theta2The helical phase mirror is placed at-A theta2The phase may be-A theta2The helical phase mirror is placed at A theta2And (3) before.
The light beam emitted by the laser 1 is collimated into parallel light by the lens group of the collimating unit 2, then enters from the plane end face of the first spiral phase mirror 3 in the vortex light beam generating device, and is emitted from the second spiral phase mirror 4 to be changed into an annular light beam, and the topological charge number of the annular light beam is determined by the angle difference of the two spiral phase mirrors after the two spiral phase mirrors rotate. Finally, focusing is carried out through a lens group in the focusing unit 5, and a light spot with annular energy distribution is obtained at the focal plane 6.
Fig. 3 is a schematic phase diagram of the first spiral phase mirror 3 in the vortex beam generating device of the present system when the modulation multiple is 1, and the phase of the second spiral phase mirror 4 is the opposite number thereof, and the positions of the two spiral phase mirrors can be switched. The phases of the two spiral phase mirrors are respectively set to be A theta2and-A θ2Wherein A is a constant and is used for controlling the change range of the topological number of the obtained vortex light beam, and theta is an azimuth angle taking the circle center of the spiral phase mirror as an origin. Starting from the initial angle alignment position of the two spiral phase mirrors, rotating the spiral phase mirrors around the optical axis, when the angle difference between the spiral phase mirrors 3 and 4 is alpha, alpha belongs to (0,2 pi), the action result of the vortex light beam generation device on the light beam is the product of the light field functions of the two spiral phase mirrors, namely exp (iA theta)2)* exp[-iA(θ-α)2]＝exp(iA2αθ-iAα2) Wherein exp (-iA alpha)2) Is a constant that has no effect on the light field. Therefore, the vortex beam generating device adds a spiral phase factor exp (i2A α θ) to the passing beam, and the topological number of the vortex is 2A α. When the angle difference between the two spiral phase mirrors is
Then, the obtained vortex topological number is 1, and each time a spiral phase mirror rotates
(radian), i.e. each increase in the angular difference between two helical phase mirrors
The topological number of the obtained vortex light beam is increased by 1, and the topological number of the vortex light beam generated by the system is continuously adjustable from an integer ranging from 0 to 4n pi. The normal line passing through the center of the helical phase mirror coincides with the optical axis.
Fig. 4 is a schematic diagram of a collimated gaussian beam according to a first embodiment of the present invention, in which the axis of the gaussian beam is aligned with the axes of the collimating mirror, the helical phase mirror and the focusing mirror.
As shown in fig. 5, when the light beam does not pass through any spiral phase plate, the light field distribution of the axial cross section of the focused light spot is obtained by only collimating the focusing unit, and the light field distribution of the focused light spot is gaussian, and the radius of the light spot is about 0.25 mm.
As shown in fig. 6, the angle difference between the two spiral phase mirrors 3 and 4 of the present invention is
In the meantime, the spiral phase factor added to the light beam by the vortex light beam generating device is exp (i θ), that is, a vortex rotation with a topological number of 1 is generated, and a light field distribution diagram of the position of the focusing unit 5 on the focusing plane 6 is shown, fig. 6 (a) is a cross-sectional light field distribution diagram, and fig. 6 (b) is an axial-sectional light field distribution diagram. Therefore, through the phase modulation of the spiral phase plate, the focusing light spot with low central energy and high edge energy and annular energy distribution is obtained, the topological charge number is 1, the phase change amount is 2 pi, and the radius of the light spot is about 0.5 mm.
FIG. 7 shows the angle difference between the two spiral phase mirrors 3, 4 of the present invention
In the meantime, the spiral phase factor added to the light beam by the vortex light beam generating device is exp (3i θ), that is, a vortex rotation with a topological number of 3 is generated, and the optical field distribution diagram of the axial section at the position of the focusing plane 6 is generated through the focusing unit 5. Therefore, through the phase modulation of the spiral phase plate, the focusing light spot with low central energy and high edge energy and annular energy distribution is obtained, the topological charge number is 3, the phase change amount is 6 pi, and the radius of the light spot is about 1 mm. The angular difference between the helical phase mirror 3 and the helical phase mirror 4 is set to a constant value by rotating the helical phase mirror
The integral multiple N of the number of the vortex rotation is obtained, the vortex rotation with the topological number of N is obtained, and the corresponding relation between the rotation angle of the spiral phase mirror and the topological charge number in the device follows the rule.
Example 3
Referring to fig. 8, the vortex light beam generating system of this embodiment further includes two scanning galvanometers, which are disposed on the light path between the vortex light beam generating device and the focusing unit 5, and the light path is switched by the two scanning galvanometers to change the focal position of the focusing plane. Other technical features of this embodiment are the same as those of embodiment 2.
After passing through the collimating unit 2 and the vortex beam generating device, the laser beam passes through the first scanning galvanometer 7, the second scanning galvanometer 9 and finally passes through the focusing objective lens, the principle of the laser beam is the same as that of the laser beam in the embodiment 1, and the focal position of the focal plane can be changed by scanning through the two galvanometers, so that fine laser processing such as marking, welding, cutting and the like can be performed.
The light path and the light field energy distribution on the focal plane of the embodiment 3 are consistent with those of the embodiment 1, and the annular light spot generated by the spiral phase mirror has the characteristic of high stability and can still maintain annular distribution at a position deviated from the focal point, so that the annular energy output can be well maintained in the process of marking by scanning the vibrating mirror through high-speed movement, and compared with the application of the embodiment 2 in a vertical space, the embodiment 3 is mainly applied in a horizontal space.
Example 4
Referring to fig. 1, the present embodiment discloses a vortex light beam generating method with an adjustable topological number, which adopts the vortex light beam generating system described in embodiment 2, and the method includes the following steps:
the laser emits laser with Gaussian light intensity, and the light beam is collimated by the collimating unit to obtain a collimated laser beam which is superposed with the central optical axes of the two spiral phase mirrors of the vortex light beam generating device;
the initial positions of two spiral phase mirrors of the vortex light beam generating device are aligned, at the moment, the vortex light beam generating device has no phase modulation effect on the passing laser beam, one of the spiral phase mirrors is rotated, and when the rotated angle is equal to
Integer multiple of N, i.e. the angular difference between the two helical phase mirrors is
Then, the vortex beam generating device adds a spiral phase factor exp (iNtheta) to the passing light beam, wherein i represents a complex symbol;
the focusing unit focuses the annular light beam emitted by the vortex light beam generating device, and the annular vortex light beam with the vortex topological number N is obtained on a focusing surface.
Example 5
Referring to fig. 8, the present embodiment discloses a vortex light beam generating method with an adjustable topological number, which adopts the vortex light beam generating system described in embodiment 3, and the method includes the following steps:
the laser emits laser with Gaussian light intensity, and the light beam is collimated by the collimating unit to obtain a collimated laser beam which is superposed with the central optical axes of the two spiral phase mirrors of the vortex light beam generating device;
the initial positions of two spiral phase mirrors of the vortex light beam generating device are aligned, at the moment, the vortex light beam generating device has no phase modulation effect on the passing laser beam, one of the spiral phase mirrors is rotated, and when the rotated angle is equal to
Integer multiple of N, i.e. the angular difference between the two helical phase mirrors is
Then, the vortex beam generating device adds a spiral phase factor exp (iNtheta) to the passing light beam, wherein i represents a complex symbol;
the annular light beam emitted by the vortex light beam generating device passes through the first scanning galvanometer 7, the second scanning galvanometer 9 and finally the focusing unit, and the two galvanometers scan to change the focal position of the focal plane and perform fine laser processing such as marking, welding, cutting and the like; the first scanning galvanometer 7 is driven by a motor 8 connected with the first scanning galvanometer, and the second scanning galvanometer 9 is driven by a motor 10 connected with the second scanning galvanometer.
The focusing unit focuses the annular light beam emitted by the vortex light beam generating device, and the annular vortex light beam with the vortex topological number N is obtained on a focusing surface.
The collimating unit and the focusing unit in the optical system of the invention use the optical elements of the combined lens group and the spiral phase lens group contained in the vortex light beam generating device, and the optical axis is ensured to be coincident with the incident light beam, and the optical element also rotates around the shaft when the spiral phase lens rotates. The phases of two spiral phase mirrors included in the vortex light beam generating device are respectively A theta2and-A θ2The positions can be interchanged, wherein A is a constant and needs to be preset, different A correspond to different spiral phase mirror structures, and the larger A corresponds to the larger variation range of the number of the topologies which can be modulated by the system. According to the spiral phase mirror, with reference to the prior art, the thickness of the spiral phase mirror can be calculated according to the material refractive index and the phase distribution of the spiral phase mirror, the height of each step is calculated when the thickness of each step reaches each step on average, corresponding manufacturing and processing are carried out, the spiral phase mirror is prepared by self, the higher the processing precision is, the better the processing precision is, and the height of each step is generally in the micrometer order; of course, they may also be purchased. The collimating unit and the focusing unit in the optical system of the present invention may be a generally conventional collimating focusing lens.
Compared with the prior art, the technical scheme provided by the invention has the advantages that two spiral phase mirrors are combined to generate the vortex rotation with adjustable topological numbers for the first time, aiming at the problem that the energy of the focused light spots with Gaussian energy distribution is concentrated and the edge energy is insufficient in laser processing. The invention utilizes the relation that the phase of two spiral phase mirrors changes along with the angle, obtains vortex light with different topological numbers in a rotating mode, and the mode is flexible, easy to realize and low in cost, the step height of the spiral phase mirrors is usually in micron magnitude, and the initial light beams are expanded by a beam expanding system and basically not dispersed, so that the spiral phase mirrors basically do not attenuate the light beam intensity, but only change the phase of the light beams, and the purity of the generated annular light beams is higher for a light source with good monochromaticity.
In general, the invention designs a group of spinning spiral phase mirrors with a second-order nonlinear spiral structure, generates vortex beams with adjustable topological numbers in a superposition manner, and forms annular light spots with energy distribution concentrated on the edge, larger diameter, longer focal depth and adjustable size. The optical system for generating the vortex rotation with adjustable topological number can obtain the annular energy distribution light spot with low light intensity loss, adjustable light spot size, low central energy and high edge energy, and can be used in a plurality of laser processing fields such as laser cutting, marking, cladding and the like. The laser thick plate cutting device effectively solves the negative problems of uneven cutting section, ablation and the like of a laser thick plate caused by overhigh central energy and insufficient edge energy of a Gaussian beam in the prior art, and is adjustable in spot size, flexible in use method, high in energy utilization rate and suitable for high-power laser processing.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (6)
1. The utility model provides a topological number adjustable vortex beam generation device which characterized in that: comprises two spiral phase mirrors, the phases of the two spiral phase mirrors are respectively set to be A theta2and-A θ2A is a constant and is used for controlling the change range of the topological number of the obtained vortex light beam, the obtained vortex optical rotation topological number is all integers from 0 to 4A pi, theta is an azimuth angle taking the circle center of the spiral phase mirror as an origin, the two spiral phase mirrors are sequentially arranged on the light path, the laser beam sequentially passes through the two spiral phase mirrors and is attached with a spiral phase factor with the set topological number to be changed into an annular vortex light beam, the topological number of the obtained vortex light beam is adjusted by rotating one or two spiral phase mirrors to control the angle difference of the two spiral phase mirrors, and the angle difference of the two spiral phase mirrors is
Integer multiples of; starting from the initial angle alignment position of the two spiral phase mirrors, rotating the spiral phase mirrors around the optical axis, when the angle difference of the two spiral phase mirrors is alpha, alpha belongs to (0,2 pi), the action result of the vortex light beam generation device on the light beam is the product of the light field functions of the two spiral phase mirrors, namely exp (iA theta2)*exp[-iA(θ-α)2]＝exp(iA2αθ-iAα2) Wherein exp (-iA alpha)2) Is a constant which has no influence on the light field, therefore, the vortex light beam generating device adds a spiral phase factor exp (i2A alpha theta) to the passing light beam, and the vortex topological number is 2A alpha; when the angle difference between the two spiral phase mirrors is increased
The topological number of the obtained vortex light beam is increased by 1;
the spiral phase mirror comprises two end faces, wherein one end face is a plane end face, the other end face is a step end face which takes the center as an origin and has a spiral shape with the height changing along with an azimuth angle, and the surface shape of the step end face is only related to the refractive index of a material, the phase setting and the laser wavelength; moreover, for any spiral phase mirror, the central axis of the spiral phase mirror is coincident with the light beam of the collimation laser beam, the laser beam can be incident from the plane end face of the corresponding spiral phase mirror or can be incident from the step end face of the corresponding spiral phase mirror, and the light beam passes through the two spiral phase mirrors to carry out phase modulation;
a first spiral phase mirror of the two spiral phase mirrors is connected with a first driving device and is driven to rotate around the central axis of the first spiral phase mirror through the first driving device, or/and a second spiral phase mirror of the two spiral phase mirrors is connected with a second driving device and is driven to rotate around the central axis of the second spiral phase mirror through the second driving device;
the central axes of the two spiral phase mirrors are positioned on the same straight line.
2. A vortex light beam generation system with adjustable topological number is characterized in that: comprising a collimating unit, a focusing unit and a vortex beam generating device according to claim 1, said vortex beam generating device being arranged on the optical path between the collimating unit and the focusing unit;
the collimation unit is used for collimating the input laser to obtain a collimated laser beam;
the vortex beam generating device is used for adding spiral phase factors corresponding to the topological charge number to the collimated laser beams emitted by the collimating unit to form annular beams, and the topological charge number of the annular beams is determined by the angle difference of the two spiral phase mirrors;
the focusing unit is used for focusing the annular light beam emitted by the vortex light beam generating device to obtain light spots with annular energy distribution.
3. A vortex beam generating system according to claim 2, wherein: the two scanning galvanometers are arranged on a light path between the vortex light beam generating device and the focusing unit, and the light path is switched through the two scanning galvanometers to change the focus position of a focusing surface.
4. A vortex beam generating system according to claim 2, wherein: and a laser is arranged in front of the collimation unit, the laser emitted by the laser is used as the input laser of the collimation unit, and the laser emitted by the laser is laser with the light intensity in Gaussian distribution.
5. A vortex beam generating method with adjustable topological number, which is characterized in that the vortex beam generating device of claim 1 is adopted, and the method comprises the following steps:
the laser emits laser with Gaussian light intensity, and the light beam is collimated by the collimating unit to obtain a collimated laser beam which is superposed with the central optical axes of the two spiral phase mirrors of the vortex light beam generating device;
the initial positions of two spiral phase mirrors of the vortex light beam generating device are aligned, at the moment, the vortex light beam generating device has no phase modulation effect on the passing laser beam, one of the spiral phase mirrors is rotated, and when the rotated angle is equal to
Integer multiple of N, i.e. the angular difference between the two helical phase mirrors is
While, the vortex beam generating device adds a spiral phase factor exp (iNtheta) to the passing beam;
the focusing unit focuses the annular light beam emitted by the vortex light beam generating device, and the annular vortex light beam with the vortex topological number N is obtained on a focusing surface.
6. The method of claim 5, wherein: two scanning galvanometers are arranged on a light path between the vortex light beam generating device and the focusing unit, and the light path is switched through the two scanning galvanometers to change the focus position of a focusing surface.
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107024768A (en) * | 2017-05-31 | 2017-08-08 | 华侨大学 | A kind of light spot shape modulating system and method based on vortex beams |
| CN107976815A (en) * | 2018-01-11 | 2018-05-01 | 苏州大学 | The forming method of rotating vortex light beam |
| CN211956009U (en) * | 2020-01-16 | 2020-11-17 | 华中科技大学 | Optical system with annular light spots |
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- 2020-12-10 CN CN202011436316.7A patent/CN112540457B/en active Active
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN107024768A (en) * | 2017-05-31 | 2017-08-08 | 华侨大学 | A kind of light spot shape modulating system and method based on vortex beams |
| CN107976815A (en) * | 2018-01-11 | 2018-05-01 | 苏州大学 | The forming method of rotating vortex light beam |
| CN211956009U (en) * | 2020-01-16 | 2020-11-17 | 华中科技大学 | Optical system with annular light spots |
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