Laser beam spatial dynamic shaping device and method

Abstract

The present invention discloses a device and method for dynamic spatial shaping of a laser beam. The device comprises: a laser pre-splitting unit, a laser spatial modulation unit, and an optical path conversion unit, which are arranged in sequence; the laser pre-splitting unit pre-splits the incident laser beam; the laser spatial modulation unit further splits the two pre-splitted laser beams to obtain two 0th-order diffraction laser beams, one 1st-order diffraction laser beam, and one +1st-order diffraction laser beam; the driving power and driving frequency of the laser spatial modulation unit are adjustable, the driving power modulating the intensity of the four diffraction laser beams, and the driving frequency modulating the angles of the 1st-order diffraction laser beam and the +1st-order diffraction laser beam; the optical path conversion unit changes the direction of the modulated four diffraction laser beams to form a combined laser beam, forming a shaped light spot on the working surface. High-speed dynamic shaping of a Gaussian beam is achieved by two sets of beam-forming devices.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronics and laser technology, and more specifically, relates to a device and method for dynamic spatial shaping of a laser beam. Background Art

[0002] Traditional laser processing often uses a Gaussian laser beam. This beam pattern has high energy at the center and low energy at the periphery. This pattern leads to uneven thermal ablation during processing, resulting in poor processing quality and severe thermal effects. With the rapid development of laser processing toward precision manufacturing, laser processing has placed greater demands on the spatial distribution of laser spot intensity. For example, the use of flat-top homogenized spots, hollow spots, and strip-shaped spots is required. This requires shaping traditional Gaussian beams into laser beams with other spot characteristics. Therefore, laser beam spatial shapers have become a core component for light field control in laser precision processing.

[0003] The main function of a dynamic spatial laser beam shaper is to redistribute the energy of a high-energy / power Gaussian laser beam in spatial shape to achieve different spatial beam shapes to suit different processing requirements. Based on the principle of beam transformation, laser shapers can be divided into refractive laser shapers and diffractive laser shapers. Traditional refractive shapers, such as lens arrays and prism arrays, refract the input laser. Diffractive laser shapers use the diffraction properties of light to control the phase and intensity of the laser wavefront at different locations on the device surface. The light beams at each location are diffracted, transmitted, and interfered with each other to achieve spatial shaping of the laser beam. Currently, there are a variety of optical devices that can be used to make diffraction shapers, including DOE elements, diffraction microlens arrays, and liquid crystal-based spatial light modulators.

[0004] However, traditional refractive shaping has a single transformation method and low modulation accuracy; the DOE elements in the diffraction laser shaper are complex to manufacture and have high requirements for the beam characteristics of the incident light. Various beam transformation effects require the coordinated use of different DOE elements, which increases system costs. The diffraction microlens array has high requirements for the beam characteristics of the incident light and has low spatial resolution. The liquid crystal-based spatial light modulator can dynamically adjust the spatial phase, intensity and polarization state of the light beam, but it is expensive and has a low optical threshold power, making it unsuitable for shaping high average power, high peak power, and large single pulse energy lasers. Summary of the Invention

[0005] In view of the defects of the related art, the purpose of the present invention is to provide a laser beam spatial dynamic shaping device and method, aiming to solve the problems of complex structure, high device cost and large size of high-power laser beam shaping system.

[0006] To achieve the above-mentioned object, in a first aspect, the present invention provides a laser beam spatial dynamic shaping device, comprising: a laser pre-splitting unit, a laser spatial modulation unit and an optical path conversion unit arranged in sequence;

[0007] The laser pre-splitting unit is used to pre-split the incident laser beam into two laser beams with an included angle of twice the Bragg diffraction angle;

[0008] The laser spatial modulation unit is used to split the two pre-split laser beams again to obtain two 0th order diffraction laser beams, one -1st order diffraction laser beam and one +1st order diffraction laser beam;

[0009] The driving power and driving frequency of the laser spatial modulation unit are adjustable, the driving power is used to modulate the intensity of the four diffracted laser beams, and the driving frequency is used to modulate the angles of a -1st order diffracted laser beam and a +1st order diffracted laser beam;

[0010] The optical path conversion unit is used to change the directions of the modulated four diffracted laser beams to form a combined laser beam, thereby forming a shaped light spot on the working surface.

[0011] Optionally, the laser spatial modulation unit includes: an ultrasonic field generation module and an acousto-optic deflection module;

[0012] The ultrasonic field generating module is arranged at the bottom of the acousto-optic deflection module, and is used to generate an ultrasonic field to cover the acousto-optic deflection module;

[0013] The acousto-optic deflection module is arranged behind the laser pre-splitting unit along the optical path direction, and is used to make the two pre-splitting laser beams diffract under the action of the ultrasonic field to form a -1 order diffraction laser beam and a +1 order diffraction laser beam.

[0014] Optionally, the ultrasonic field generating module includes a radio frequency driving power supply, a piezoelectric transducer and an acousto-optic interaction medium;

[0015] The acousto-optic interaction medium is arranged in the acousto-optic deflection module;

[0016] The piezoelectric transducer is a thin sheet with piezoelectric properties attached to the surface of the acousto-optic interaction medium, and the electrode layers at both ends of the piezoelectric layer in the piezoelectric transducer are connected to the radio frequency driving power supply;

[0017] The RF driving power supply is used to act on the piezoelectric transducer under the drive of the RF signal, so that the piezoelectric transducer vibrates at a high frequency and forms an energy-adjustable ultrasonic field with volume grating properties with the acousto-optic interaction medium.

[0018] Optionally, the acousto-optic interaction medium is any one of fused quartz, quartz crystal, single crystal germanium, tellurium oxide or lead molybdate.

[0019] Optionally, the optical path transformation unit adopts a lens or a lens group.

[0020] In a second aspect, the present invention further provides a method for dynamic spatial shaping of a laser beam, applicable to a device for dynamic spatial shaping of a laser beam as described in any one of the first aspects, comprising:

[0021] S1, based on the wavelength of the incident laser beam, the parameters of the laser spatial modulation unit and the angle θ between the two laser beams after pre-splitting B0 , calculate the position and intensity distribution of the shaped light spot;

[0022] S2. Calculating target driving power parameters and target driving frequency parameters of the laser spatial modulation unit according to the position and intensity distribution of the shaped light spot and the position and intensity distribution of the target light spot;

[0023] S3. Adjust the laser spatial modulation unit according to the target driving power parameter and the target driving frequency parameter to dynamically modulate and shape the incident laser beam.

[0024] Optionally, S1 includes:

[0025] S11. Calculate the angles 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser in the four diffraction laser beams generated after the two pre-splitting laser beams are split and modulated in the laser spatial modulation unit. B ;

[0026] S12, according to the angle 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser B , the angle 2θ between the two laser beams after pre-splitting B0 As well as the parameters of the laser spatial modulation unit, the intersection positions y1 and y2 of the reverse extension lines of the -1st and +1st order diffracted lasers and the laser pre-beam splitting unit are determined respectively; the calculation formula is as follows:

[0027]

[0028] Wherein, l3 is the length of the acousto-optic interaction medium;

[0029] S13, calculating the positions y1′ and y2′ of the light spots after -1st and +1st order diffraction laser shaping using the lens formula;

[0030]

[0031] Wherein, l1 is the distance between the optical path conversion unit and the incident laser beam waist position, l2 is the distance between the optical path conversion unit and the working surface of the device;

[0032] S14. Obtain the light intensity distribution of the Gaussian light spots at y1′, y2′, and o′ after laser beam shaping, wherein o′ is the position of the light spots after the two beams of 0th-order diffraction laser beams are shaped.

[0033] Optionally, the distance relationship between the optical path conversion unit, the laser spatial modulation unit and the working surface of the device satisfies the object-image relationship formula of the lens:

[0034]

[0035] Wherein, F is the focal length of the laser spatial modulation unit.

[0036] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0037] (1) Only two beam splitters are used to split and shape the incident laser beam, and output the corresponding shaped laser beam, making the entire system more flexible and controllable. Compared with traditional shaping systems, the optical path is simpler and easier to debug.

[0038] (2) For the spatial modulation unit, its diffraction efficiency and diffraction angle are related to the driving power and driving frequency. By changing the driving power, the energy of the diffracted light can be controlled; by changing the driving frequency, the direction of the diffracted beam can be controlled, thereby dynamically splitting and modulating the laser beam, and finally the optical path conversion unit converges it into a shaped light spot. The spatial modulation unit does not need to switch multiple sets of shaping mirrors or diffraction optical devices. On the basis of reducing the size of the device, the driving intensity and driving frequency can be switched within 10us, thereby achieving high-speed dynamic beam modulation and shaping. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram showing the principle of a laser beam spatial dynamic shaping device provided in the first embodiment of the present invention;

[0040] Figure 2 A schematic diagram of the optical path of a laser beam in a laser beam spatial dynamic shaping device provided in Example 1 of the present invention;

[0041] Figure 3A A schematic diagram of a light spot intensity distribution generated by a laser beam spatial dynamic shaping device provided in the second embodiment of the present invention;

[0042] Figure 3B A schematic diagram of another light spot intensity distribution generated by a laser beam spatial dynamic shaping device provided in the second embodiment of the present invention;

[0043] Figure 3C This is a schematic diagram of another light spot intensity distribution generated by a laser beam spatial dynamic shaping device provided in the second embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0045] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0046] Example 1

[0047] like Figure 1 As shown, a laser beam spatial dynamic shaping device comprises: a laser pre-splitting unit 1, a laser spatial modulation unit 2 and an optical path transformation unit 3 arranged in sequence;

[0048] The laser pre-splitting unit 1 is used to pre-split the incident laser beam into two laser beams with an angle equal to twice the Bragg diffraction angle;

[0049] The laser spatial modulation unit 2 is used to split the two pre-split laser beams again to obtain two 0th order diffraction laser beams, one -1st order diffraction laser beam and one +1st order diffraction laser beam;

[0050] The driving power and driving frequency of the laser spatial modulation unit 2 are adjustable. The driving power is used to modulate the intensity of the four diffracted laser beams, and the driving frequency is used to modulate the angles of a -1st order diffracted laser beam and a +1st order diffracted laser beam.

[0051] The optical path conversion unit 3 is used to change the directions of the modulated four diffracted laser beams to form a combined laser beam, thereby forming a shaped light spot on the working surface.

[0052] The laser pre-splitting unit 1 pre-splits the incident laser beam based on a diffraction optical element or an acousto-optic element, and splits it into two laser beams with an angle of twice the Bragg diffraction angle, so that the laser spatial modulation unit 2 can split the two pre-split laser beams again based on the principle of acousto-optic Bragg diffraction to perform modulation and shaping. In this embodiment, the laser pre-splitting unit 1 uses a diffraction optical element. In order to simplify the calculation formula and make the device more compact, in this embodiment, the pre-splitting unit 1 is set to be closely attached to the laser spatial modulation unit 2, such as Figure 1 、 Figure 2 As shown in . Further, the waist position of the incident laser beam is preferably located at the joint surface of the pre-beam splitting unit 1 and the laser spatial modulation unit 2 to achieve the best beam splitting effect. Figure 1As shown, the laser spatial modulation unit 2 uses the acousto-optic Bragg diffraction principle to split the pre-split laser again to obtain two 0-order laser beams, one -1-order diffraction laser beam and one +1-order diffraction laser beam, a total of 4 laser beams. Figure 2 As shown, by adjusting the driving power of the laser spatial modulation unit 2, the intensity of the four laser beams can be changed; by adjusting the driving frequency of the laser spatial modulation unit 2, the Bragg angle can be changed, that is, the angle of a beam of -1 order diffraction laser and a beam of +1 order diffraction laser can be changed to achieve modulation of the intensity and angle of the laser beam in space. The optical path conversion unit 3 uses a lens or a lens group to combine the modulated four laser beams. In this embodiment, the lens of the optical path conversion unit 3 is a focusing lens. Figure 1 , after beam combining, the four laser beams converge on a plane, that is, the four laser beams converge on the working surface of the device. The centers of the four laser beams do not completely overlap, and the centers of the two 0-level laser beams split by the laser spatial modulation unit 2 overlap at one point, and the +1-level and -1-level laser beams have a certain separation distance. Since the laser beam has a width, if the separation distance between the four laser beams is less than or equal to the laser beam width, the combined laser beam at the final position can be regarded as a laser beam. For example, Figure 1 As shown, the width of the four laser beams is 2w, the two 0-level laser beams overlap, the +1-level laser beam is located above the 0-level laser, and the -1-level laser beam is located below the 0-level laser beam. When the distance between the center of the +1-level laser beam and the center of the 0-level laser beam is less than or equal to 2w, and the distance between the center of the 0-level laser beam and the center of the -1-level laser beam is less than or equal to 2w, the four laser beams can be considered as one laser beam. The intensity and center position of the 0-level, +1-level and -1-level laser beams can be modulated by the laser spatial modulation unit 2, so that the shape of the final combined laser beam can be changed, realizing the laser shaping effect. Furthermore, a photodetector can be set at the working surface of the device to observe the light spot after the combined laser beam is shaped and measure the energy distribution of the light spot.

[0053] Optional, such as Figure 1 As shown, the laser spatial modulation unit 2 includes: an ultrasonic field generating module 2.1 and an acousto-optic deflection module 2.2;

[0054] The ultrasonic field generating module 2.1 is arranged at the bottom of the acousto-optic deflection module 2.2, and is used to generate an ultrasonic field to cover the acousto-optic deflection module 2.2;

[0055] The acousto-optic deflection module 2.2 is arranged behind the laser pre-splitting unit 1 along the optical path direction, and is used to make the two pre-splitting laser beams diffract under the action of the ultrasonic field to form a -1 order diffraction laser beam and a +1 order diffraction laser beam.

[0056] like Figure 1As shown in the figure, the incident light I0 is incident vertically on the laser pre-beam splitting unit 1. Since the beam waist position of the incident light I0 is at the joint plane of the laser pre-beam splitting unit 1 and the laser spatial modulation unit 2, the best beam splitting effect can be achieved, and this position is recorded as o. Therefore, when designing a laser beam spatial dynamic shaping device, the Bragg diffraction angle θ can be calculated by the formula B0 :

[0057]

[0058] Wherein, λ is the wavelength of the incident light, f0 is the driving center frequency of the laser spatial modulation unit 2, n is the refractive index of the acousto-optic interaction medium of the laser spatial modulation unit 2, and v is the acoustic wave velocity in the acousto-optic interaction medium of the laser spatial modulation unit 2.

[0059] like Figure 2 As shown, the laser pre-splitting unit 1 splits I0 into two beams with an angle of twice the Bragg diffraction angle 2θ. B0 There are two horizontally symmetrical laser beams I1 and I2, and the angle between each laser beam and the horizontal is θ B0 .

[0060] refer to Figure 1 and Figure 2 The ultrasonic field generating module 2.1 is used to generate an ultrasonic field on the acousto-optic deflection module 2.2, and the acousto-optic deflection module 2.2 is used to receive the Bragg diffraction angle θ B0 The incident light I1 and I2 are deflected along the plane of the ultrasonic field after passing through the ultrasonic field and diffracted at the Bragg diffraction angle θ B The +1st order diffraction light I5 and -1st order diffraction light I4 are emitted, and the angles between I5 and I4 and the undeflected 0th order diffraction light I3 and I6 are 2θ. B Specifically, the angle between I4 and I3 is 2θ B , the angle between I5 and I6 is 2θ B .like Figure 2 As shown, the undeflected outgoing light forms zero-order diffracted light I3 and I6. The laser spatial modulation unit 2 splits the incident light I1 and I2 into four laser beams I3 to I6.

[0061] Laser beams I3-I6 change their deflection directions under the action of optical path transformation unit 3, forming a combined laser beam, which forms a shaped light spot on the working surface of the device. The photodetector observes the shaped light spot of the combined laser beam and measures the energy distribution of the light spot.

[0062] Before the laser beam spatial dynamic shaping device is used for shaping, the angle θ at which the incident light is deflected under the action of the ultrasonic field is calculated based on the preset spot position. B, thereby determining the initial drive power and frequency of the laser spatial modulation unit, and calculating the distance between each unit based on the positional relationship. Because the incident light is deflected in the direction under the action of the ultrasonic field, when the formed light spot needs to be quickly shaped, the target drive power parameters and target drive frequency parameters of the laser spatial modulation unit can be calculated based on the position of the shaped light spot and the target light spot. By changing the drive power and drive frequency of the ultrasonic field generation module 2.1, the direction and light intensity of laser beams I3-I6 are modulated, thereby achieving high-speed dynamic laser shaping.

[0063] Optionally, the ultrasonic field generating module 2.1 includes a radio frequency driving power supply, a piezoelectric transducer and an acousto-optic interaction medium;

[0064] The acousto-optic interaction medium is arranged in the acousto-optic deflection module 2.2;

[0065] The piezoelectric transducer is a thin sheet with piezoelectric properties attached to the surface of the acousto-optic interaction medium, and the electrode layers at both ends of the piezoelectric layer in the piezoelectric transducer are connected to the radio frequency driving power supply;

[0066] The RF driving power supply is used to act on the piezoelectric transducer under the drive of the RF signal, so that the piezoelectric transducer vibrates at a high frequency and forms an energy-adjustable ultrasonic field with volume grating properties with the acousto-optic interaction medium.

[0067] During operation, the RF driver operates under the influence of an RF signal, converting electrical motion into mechanical motion at the piezoelectric transducer. When this mechanical motion acts on the acousto-optic interaction medium, an energy-adjustable ultrasonic field with volume grating properties is generated. The piezoelectric transducer comprises an LN crystal, and the acousto-optic interaction medium can be fused quartz, quartz crystal, single crystal germanium, tellurium oxide, or lead molybdate.

[0068] The technical solution of this embodiment utilizes two sequentially arranged beam-splitting devices: a laser pre-splitting unit and a laser spatial modulation unit. These split, modulate, and shape the incident laser beam, outputting a corresponding shaped laser beam, making the entire system more flexible and controllable. Furthermore, by varying the driving power and frequency of the laser spatial modulation unit, the energy and deflection direction of the diffracted light can be controlled, thereby dynamically splitting and modulating the laser beam. This addresses the technical issues of complex, costly, and bulky high-power laser beam shaping systems, simplifying the system's design while reducing the device's size while achieving the beneficial effect of high-speed dynamic beam modulation and shaping.

[0069] Example 2

[0070] A laser beam spatial dynamic shaping method, applicable to a laser beam spatial dynamic shaping device as described in any one of the above embodiments, comprising:

[0071] S1, based on the wavelength of the incident laser beam, the parameters of the laser spatial modulation unit and the angle θ between the two laser beams after pre-splitting B0 , calculate the position and intensity distribution of the shaped light spot;

[0072] S2. Calculating target driving power parameters and target driving frequency parameters of the laser spatial modulation unit according to the position and intensity distribution of the shaped light spot and the position and intensity distribution of the target light spot;

[0073] S3. Adjust the laser spatial modulation unit according to the target driving power parameter and the target driving frequency parameter to dynamically modulate and shape the incident laser beam.

[0074] Optionally, S1 includes:

[0075] S11. Calculate the angles 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser in the four diffraction laser beams generated after the two pre-splitting laser beams are split and modulated in the laser spatial modulation unit. B .

[0076] refer to Figure 1 and Figure 2 The laser pre-splitting unit 1 splits I0 into two beams with an angle of twice the Bragg diffraction angle 2θ. B0 Two horizontally symmetrical laser beams I1 and I2, θ B0 It can be calculated by the formula:

[0077]

[0078] Wherein λ is the wavelength of the incident light, f0 is the driving center frequency of the laser spatial modulation unit 2, n is the refractive index of the interaction medium of the laser spatial modulation unit 2, and v is the acoustic wave velocity in the acousto-optic interaction medium of the laser spatial modulation unit 2.

[0079] The incident light beams I1 and I2 are diffracted at the Bragg angle θ B0 The incident laser spatial modulation unit 2 splits the incident light beam I1 into 0th-order diffraction laser I3 and -1st-order diffraction laser I4, and the incident light beam I2 into 0th-order diffraction laser I6 and +1st-order diffraction laser I5. Assume that the refractive index of the acousto-optic interaction medium is n, the speed of sound in the medium is v, and the sound frequency is f; the wavelength of the incident light in air is λ. The Bragg diffraction angle θ B It can be expressed as:

[0080]

[0081] The angle between the split laser beams I4 and I5 and the 0th order diffraction laser is twice the Bragg diffraction angle 2θ. B, then the angle between I3 and I4 and the angle between I5 and I6 are 2θ B .

[0082] S12, according to the angle 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser B , the angle 2θ between the two laser beams after pre-splitting B0 As well as the parameters of the laser spatial modulation unit, the intersection positions y1 and y2 of the reverse extension lines of the -1st and +1st order diffracted lasers and the laser pre-beam splitting unit are determined respectively; the calculation formula is as follows:

[0083]

[0084] Where l3 is the length of the acousto-optic interaction medium.

[0085] Make reverse extension lines for I4 and I5, the reverse extension line of I4 intersects the bonding surface of the laser pre-beam splitting unit 1 and the laser spatial modulation unit 2 at y1, and the reverse extension line of I5 intersects the bonding surface of the laser pre-beam splitting unit 1 and the laser spatial modulation unit 2 at y2.

[0086] Based on the principle of acousto-optic deflection, the beam waist positions of 0th-order diffracted beams I3 and I6 are consistent with those of I1 and I2, both located at o. The beam waist positions of ±1st-order diffracted beams I4 and I5 are located at y1 and y2, respectively. Optical path transformation unit 3 transforms laser beams I3-I6, which is equivalent to performing a lens transformation on the beam waists of I3-I6. Therefore, the position of the working surface can be determined using the lens transformation formula.

[0087] The distance relationship between the optical path conversion unit, the laser spatial modulation unit and the working surface of the device satisfies the object-image relationship formula of the lens:

[0088]

[0089] Wherein, F is the focal length of the laser spatial modulation unit, l1 is the distance between the optical path conversion unit and the incident laser beam waist position, and l2 is the distance between the optical path conversion unit and the working surface of the device.

[0090] S13, calculating the positions y1′ and y2′ of the light spots after -1st and +1st order diffraction laser shaping using the lens formula;

[0091]

[0092] Wherein, l1 is the distance between the optical path transformation unit and the incident laser beam waist position, and l2 is the distance between the optical path transformation unit and the working surface of the device.

[0093] like Figure 1 、 Figure 2As shown, after passing through the laser pre-splitting unit 1, the laser spatial modulation unit 2 and the optical path transformation unit 3, the laser beams I3 to I6 have Gaussian spots at three positions y1′, y2′ and o′ on the working surface 4, I3 and I6 form I8 at o′, I5 forms I7 at y1′, and I4 forms I9 at y2′.

[0094] S14. Obtain the light intensity distribution of the Gaussian light spots at y1′, y2′, and o′ after laser beam shaping, wherein o′ is the position of the light spots after the two beams of 0th-order diffraction laser beams are shaped.

[0095] The diffraction efficiency η is defined as the ratio of the +1st or -1st order diffracted light intensity to the incident light intensity. In this example, the reference Figure 1 The intensity of each beam is indicated by the formula based on the principle of acousto-optic Bragg diffraction:

[0096]

[0097] Among them, the acoustic and optical figure of merit is M2, and the sound power is P s ; The width of the piezoelectric transducer is H and the length is L; the wavelength of the incident light in air is λ.

[0098] According to the law of conservation of energy, the intensity of the 0th order diffraction light I3 and I6 can be obtained:

[0099] I3=I3=I1(1-η)=I2(1-η)

[0100] Assume that the incident Gaussian beam waist is ω. Based on the Gaussian beam waist intensity distribution formula, the intensity distribution at the beam waist position can be expressed as:

[0101]

[0102] The intensity distribution of the three Gaussian spots can be expressed as

[0103]

[0104] When y1′ and y2′ are less than or equal to the Gaussian beam waist ω, I7 to I9 can be considered as a beam of light I out , and its spot distribution is

[0105] I out (x′,y′)=I7(x′,y′)+I8(x′,y′)+I9(x′,y′)

[0106] Furthermore, the laser pre-splitting unit 1 splits I0 into equal power beams, i.e., I1=I2=0.5I0, and the symmetrically distributed output spot distribution can be obtained as follows:

[0107]

[0108] In practical applications, a photodetector can be set at the working surface 4 to assist in detecting the distribution of the observed light spot and facilitate adjustment. The light spot distribution can be adjusted by adjusting the driving frequency and driving power of the laser spatial modulation unit 2. Specifically, by adjusting the driving power of the laser spatial modulation unit 2, the size of η can be controlled, thereby controlling the energy distribution of the light beam. By adjusting the driving frequency of the laser spatial modulation unit 2, the acousto-optic Bragg diffraction angle θ can be controlled. B , thereby controlling the center positions y1′ and y2′ of the Gaussian spot.

[0109] Therefore, in this embodiment, the spatial distribution of the output light intensity can be dynamically modulated and beam shaped simply by controlling the driving power and frequency of the laser spatial modulation unit 2. The switching time between different shaping modes depends on the driving method of the laser spatial modulation unit 2. Currently, DDS-based driving methods can switch between different driving frequencies and powers within 10 μs, achieving high-speed dynamic shaping of the laser beam.

[0110] For example, the piezoelectric transducer has a width of H = 3 mm, a length of L = 18 mm, an acousto-optic interaction medium is a quartz crystal, a crystal length l3 = 20 mm, a refractive index n = 1.55, and an acousto-optic figure of merit M2 = 3.5 × 10 -15 s 3 / kg, sound center frequency f0 = 68MHz, sound speed in the medium v ​​= 5750m / s, incident light wavelength λ = 1064nm, incident laser beam waist ω = 2.0mm, Bragg diffraction angle θ B0 for:

[0111]

[0112] Under the initial condition of the laser spatial modulation unit driving frequency f=f0=68MHz, there is θ B =θ B0 With the goal of ultimately falling on the working surface, y1′=ω, y2′=-ω, the equations can be listed:

[0113]

[0114] The equation is solved to get l2=25l1, and the positional relationship between the optical path conversion unit and other units is adjusted.

[0115] When the laser spot is required to be shaped into a flat-top distribution spot, η is preferably 70%. At this time, the distribution of light intensity on the y' axis is as follows: Figure 3A As shown, an approximately flat-top laser spot distribution is obtained; when the laser spot is required to be shaped into a double spot distribution, η is preferably higher than 90%. At this time, the distribution of light intensity on the y′ axis is as follows Figure 3BAs shown, two light spots with separated centers are obtained. The interval 2y1′ between the two light spots is controlled by adjusting the driving frequency f of the laser spatial modulation unit. When the laser spot is required to maintain a Gaussian distribution, η is preferably 0%. At this time, the distribution of light intensity on the y′ axis is as follows: Figure 3C shown.

[0116] The technical solution of the embodiment of the present invention controls the diffraction efficiency and diffraction angle of the laser beam in the laser spatial modulation unit by controlling the driving efficiency and driving frequency of the laser spatial modulation unit, without switching multiple sets of shaping mirror groups or diffraction optical devices. On the basis of reducing the volume of the device, high-speed dynamic shaping of the Gaussian beam based on the principle of acousto-optic deflection is achieved.

[0117] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A laser beam spatial dynamic shaping device, characterized in that: include: A laser pre-splitting unit, a laser spatial modulation unit and an optical path conversion unit are arranged in sequence; The laser pre-splitting unit is used to pre-split the incident laser beam into two laser beams with an included angle of twice the Bragg diffraction angle; The laser spatial modulation unit is used to split the two pre-split laser beams again to obtain two 0th order diffraction laser beams, one -1st order diffraction laser beam and one +1st order diffraction laser beam; The driving power and driving frequency of the laser spatial modulation unit are adjustable, the driving power is used to modulate the intensity of the four diffracted laser beams, and the driving frequency is used to modulate the angles of a -1st order diffracted laser beam and a +1st order diffracted laser beam; The optical path conversion unit is used to change the directions of the modulated four diffracted laser beams to form a combined laser beam, thereby forming a shaped light spot on the working surface.

2. The device according to claim 1, wherein The laser spatial modulation unit includes: an ultrasonic field generation module and an acousto-optic deflection module; The ultrasonic field generating module is arranged at the bottom of the acousto-optic deflection module, and is used to generate an ultrasonic field to cover the acousto-optic deflection module; The acousto-optic deflection module is arranged behind the laser pre-splitting unit along the optical path direction, and is used to make the two pre-splitting laser beams diffract under the action of the ultrasonic field to form a -1 order diffraction laser beam and a +1 order diffraction laser beam.

3. The device according to claim 2, wherein The ultrasonic field generating module includes a radio frequency driving power supply, a piezoelectric transducer and an acousto-optic interaction medium; The acousto-optic interaction medium is arranged in the acousto-optic deflection module; The piezoelectric transducer is a thin sheet with piezoelectric properties attached to the surface of the acousto-optic interaction medium, and the electrode layers at both ends of the piezoelectric layer in the piezoelectric transducer are connected to the radio frequency driving power supply; The RF driving power supply is used to act on the piezoelectric transducer under the drive of the RF signal, so that the piezoelectric transducer vibrates at a high frequency and forms an energy-adjustable ultrasonic field with volume grating properties with the acousto-optic interaction medium.

4. The device according to claim 3, characterized in that The acousto-optic interaction medium is any one of fused quartz, quartz crystal, single crystal germanium, tellurium oxide or lead molybdate.

5. The device according to claim 1, wherein The optical path conversion unit adopts a lens or a lens group.

6. A method for dynamic spatial shaping of a laser beam, applicable to a device for dynamic spatial shaping of a laser beam as claimed in any one of claims 1 to 5, characterized in that: include: S1, based on the wavelength of the incident laser beam, the parameters of the laser spatial modulation unit and the angle θ between the two laser beams after pre-splitting B0 , calculate the position and intensity distribution of the shaped light spot; S2. Calculating target driving power parameters and target driving frequency parameters of the laser spatial modulation unit according to the position and intensity distribution of the shaped light spot and the position and intensity distribution of the target light spot; S3, adjusting the laser spatial modulation unit according to the target driving power parameter and the target driving frequency parameter to dynamically modulate and shape the incident laser beam; Among them, S1 includes: S11. Calculate the angles 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser in the four diffraction laser beams generated after the two pre-splitting laser beams are split and modulated in the laser spatial modulation unit. B ; S12, according to the angle 2θ between the -1st and +1st order diffraction lasers and the 0th order diffraction laser B , the angle 2θ between the two laser beams after pre-splitting B0 As well as the parameters of the laser spatial modulation unit, the intersection positions y1 and y2 of the reverse extension lines of the -1st and +1st order diffracted lasers and the laser pre-beam splitting unit are determined respectively; the calculation formula is as follows: Wherein, l3 is the length of the acousto-optic interaction medium; S13, calculating the positions y1′ and y2′ of the light spots after -1st and +1st order diffraction laser shaping using the lens formula; Wherein, l1 is the distance between the optical path conversion unit and the incident laser beam waist position, l2 is the distance between the optical path conversion unit and the working surface of the device; S14. Obtain the light intensity distribution of the Gaussian light spots at y1′, y2′, and o′ after laser beam shaping, wherein o′ is the position of the light spots after the two beams of 0th-order diffraction laser beams are shaped.

7. The dynamic shaping method according to claim 6, wherein: The distance relationship between the optical path conversion unit, the laser spatial modulation unit and the working surface of the device satisfies the object-image relationship formula of the lens: Wherein, F is the focal length of the laser spatial modulation unit.

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