CN117724278A - Phased array acousto-optic deflector using KYW crystal - Google Patents
Phased array acousto-optic deflector using KYW crystal Download PDFInfo
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- CN117724278A CN117724278A CN202311476194.8A CN202311476194A CN117724278A CN 117724278 A CN117724278 A CN 117724278A CN 202311476194 A CN202311476194 A CN 202311476194A CN 117724278 A CN117724278 A CN 117724278A
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- 239000013078 crystal Substances 0.000 title claims abstract description 93
- 230000017525 heat dissipation Effects 0.000 claims description 12
- 238000000034 method Methods 0.000 claims description 7
- GQYHUHYESMUTHG-UHFFFAOYSA-N lithium niobate Chemical compound [Li+].[O-][Nb](=O)=O GQYHUHYESMUTHG-UHFFFAOYSA-N 0.000 claims description 6
- 238000010521 absorption reaction Methods 0.000 claims description 3
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical group [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 claims description 3
- 239000010931 gold Substances 0.000 claims description 3
- 229910052737 gold Inorganic materials 0.000 claims description 3
- 229910052738 indium Inorganic materials 0.000 claims description 3
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical group [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 claims description 3
- 238000007788 roughening Methods 0.000 claims description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 abstract description 21
- 239000010453 quartz Substances 0.000 abstract description 19
- 239000000463 material Substances 0.000 abstract description 16
- 230000003287 optical effect Effects 0.000 description 8
- 230000010287 polarization Effects 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 229910052714 tellurium Inorganic materials 0.000 description 4
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 4
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 238000003466 welding Methods 0.000 description 3
- 238000004458 analytical method Methods 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000001902 propagating effect Effects 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 238000004364 calculation method Methods 0.000 description 1
- 239000003990 capacitor Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 239000005350 fused silica glass Substances 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000000382 optic material Substances 0.000 description 1
- 230000005693 optoelectronics Effects 0.000 description 1
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 description 1
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- LXRWZZFNYNSWPB-UHFFFAOYSA-N potassium yttrium Chemical compound [K].[Y] LXRWZZFNYNSWPB-UHFFFAOYSA-N 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012887 quadratic function Methods 0.000 description 1
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- 229910052814 silicon oxide Inorganic materials 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 229910001936 tantalum oxide Inorganic materials 0.000 description 1
- PBYZMCDFOULPGH-UHFFFAOYSA-N tungstate Chemical compound [O-][W]([O-])(=O)=O PBYZMCDFOULPGH-UHFFFAOYSA-N 0.000 description 1
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- Optical Modulation, Optical Deflection, Nonlinear Optics, Optical Demodulation, Optical Logic Elements (AREA)
Abstract
A phased array acousto-optic deflector using KWY crystals, comprising a KYW crystal and a plurality of planar phased array units, each planar phased array unit comprising a piezoelectric transducer, a matching network and a digital frequency synthesizer DDS matched to each other, the phase difference between the plurality of digital frequency synthesizers DDS being adjustable. In the KYW crystal, the acoustic wave is along N g Direction propagation and acoustic wave propagation along N g -30 ° directional propagation. The invention uses KYW crystal as the acousto-optic medium of the acousto-optic deflector, and the damage threshold can reach 2GW/cm 2 Compared with quartz material, the sound-light figure of merit is 7 times that of quartz material, M 2 ＝15×10 ‑15 S 3 Per Kg, the acousto-optic performance is far better than that of quartz material; the length of the electrode is increased, the radio frequency power can be effectively reduced, the scanning angle is increased, and the device is more suitable for infrared and far infrared high-power long-wave excitationLight modulation field.
Description
Technical Field
The invention relates to the field of laser modulation, in particular to a phased array acousto-optic deflector using KYW crystals
Background
The acousto-optic device can modulate the frequency, amplitude, phase and other characteristics of laser by using an electronic driving signal, and is widely applied to the fields of light beam control, optical communication, optical calculation, optical signal processing and the like along with development of optoelectronic technology.
An acousto-optic deflector is a device developed based on the principle that the incidence of a light beam into a medium injected with acoustic waves will be deflected. When the refractive index of the incident light changes periodically due to the medium under the influence of ultrasonic waves, the incident light will be deflected in one or more directions. The deflection angle can be precisely controlled by controlling the frequency of the rf driver. Compared with the traditional galvanometer scanning beam, the acousto-optic deflector has the advantages of ultrahigh scanning speed, wide spectrum range, high scanning resolution, high luminous flux and the like.
However, when the frequency bandwidth of the traditional monolithic acousto-optic deflector is increased, the electrode length can only be reduced to increase the acoustic divergence angle, the ultrasonic main direction of the acoustic wave is fixed, along the normal direction of the crystal face of the transducer, the ultrasonic main direction can not be ensured to be consistent with the direction of the acoustic wave vector meeting the momentum matching in the working frequency band range, the ultrasonic main direction can be consistent only at a certain frequency, the ultrasonic utilization rate is extremely low, the contradiction between the Bragg diffraction area and the Bragg bandwidth can occur in the selection of the transducer size in practical application, the scanning range of the device is small, the use of radio frequency power is large, and the performance and stability of the product are reduced;
meanwhile, in the field of modulation of high-power laser radiation, quartz is the only acousto-optic modulation material, the acousto-optic figure of merit is low, the acousto-optic quality is poor, the acousto-optic modulation is carried out by using extremely high radio frequency power, and the whole device needs a water cooling heat dissipation structure, so that the application is greatly complicated; compared with tellurium oxide acousto-optic medium with good acousto-optic performance, the tellurium oxide acousto-optic medium has low laser damage threshold in the use process, the light-transmitting surface is extremely easy to damage, and high laser power cannot be born.
How to develop high-efficiency acousto-optic materials with large laser damage threshold and high acousto-optic quality, and be applicable to the field of acousto-optic deflectors, bandwidth and scanning range are improved, so as to meet the development requirements of higher laser power, higher efficiency and higher beam quality, and the method is a technical problem to be solved in the prior art.
Disclosure of Invention
The invention aims to provide a phased array acousto-optic deflector using KYW crystals, which generates a larger laser scanning range and more uniform laser intensity at low radio frequency power; meanwhile, the KYW crystal has a large acousto-optic figure of merit, can reach 6-7 times of that of a quartz crystal under the same condition, has smaller device size, does not need a water cooling heat dissipation device, and has a higher damage threshold compared with tellurium oxide crystals and quartz crystals.
To achieve the purpose, the invention adopts the following technical scheme:
a phased array acousto-optic deflector using KWY crystal, comprising KYW crystal and a plurality of planar phased array units, each comprising piezoelectric transducer, matching network and digital frequency synthesizer DDS matched with each other,
the method comprises the steps that a plurality of piezoelectric transducers are arranged on a KYW crystal, the piezoelectric transducers are connected with the KYW crystal through bonding layers, and each piezoelectric transducer is connected with a matching network through an electrode layer in sequence and driven through a digital frequency synthesizer DDS;
the phase difference between the plurality of digital frequency synthesizers DDS is adjustable.
Optionally, in the KYW crystal, the acoustic wave is along N g -30 DEG direction propagation, the acousto-optic optimum value is M 2 ＝15×10 -15 S 3 /Kg。
Alternatively, the piezoelectric transducer uses a lithium x-cut niobate crystal with an acoustic velocity in the crystal of 2500m/s.
Alternatively, the piezoelectric transducers are 4, the center distance s between adjacent transducers is about 3mm, the length of each electrode layer is 2.7mm, and the total electrode length is 10.8mm.
Optionally, in the KYW crystal, the acoustic wave is along N g Direction propagation, sound-light optimum value at M 2 ＝11×10 -15 S 3 /Kg。
Alternatively, the piezoelectric transducer uses 36-Y tangential lithium niobate crystals with acoustic velocity in the crystal of 4560m/s.
Alternatively, the piezoelectric transducers are 4, the center distance s between adjacent transducers is about 3.5mm, the length of each electrode layer is 2mm, and the total electrode length is 12.8mm.
Optionally, the piezoelectric crystal is an LN crystal, and the standing wave ratio in the LC impedance matching network is less than 1.2.
Optionally, the electrode layer is a gold film with a thickness of 100-500nm, and the bonding layer is an indium film with a thickness of 200-600nm.
Optionally, a wedge angle of 30 degrees for controlling sound absorption is arranged at the bottom of the KYW acousto-optic crystal, and roughening treatment is carried out;
the bottom of the KYW acousto-optic crystal adopts a wedge-shaped heat dissipation block corresponding to the corresponding wedge angle, and the side surface adopts a main heat dissipation block to conduct heat dissipation;
the transparent surface of the KYW crystal is also provided with an antireflection film.
In summary, the invention has the following advantages:
1. the invention uses KYW crystal as acousto-optic medium of acousto-optic deflector, the damage threshold can reach 2GW/cm 2 (10 ns,10MHz,1064nm pulse laser), which is equivalent to quartz material, the acousto-optic figure of merit is 7 times that of quartz material, M 2 ＝15×10 -15 S 3 The sound and light performance of the material is far better than that of quartz materials.
2. The invention increases the length of the used electrode, can effectively reduce the radio frequency power, increases the scanning angle, and is more suitable for the field of infrared and far infrared high-power long-wave laser modulation.
3. The multi-array unit phase-shifting transducer and the DDS signal source are used, so that phase-shifting ultrasonic wave coherent superposition is performed, ultrasonic tracking is completed, bragg loss is reduced, ultrasonic energy utilization rate is improved, and compared with a traditional single-chip acousto-optic deflector, bandwidth and dynamic scanning range are effectively enlarged; the frequency, the phase and the amplitude of each array unit can be precisely controlled by a computer system, so that the ultrasonic direction meeting the phase matching is tracked, and the tracking error is reduced.
Drawings
FIG. 1 is a schematic diagram of a phased array acousto-optic deflector in accordance with an embodiment of the present invention;
FIG. 2 is a schematic diagram of the structure and optical axis of a KYW crystal according to one embodiment of the invention;
FIG. 3 is a schematic view of the structure and optical axis of a KYW crystal according to another embodiment of the present invention;
FIG. 4 is a schematic diagram of ultrasonic tracking of a phased array acousto-optic deflector in accordance with a particular embodiment of the invention;
fig. 5 is a schematic diagram of the forward structure of an acousto-optic modulator of a phased array acousto-optic deflector in accordance with a specific embodiment of the present invention.
The technical features indicated by the reference numerals in the drawings are as follows:
1. KYW crystals; 2. a piezoelectric transducer; 3. a matching network; 4. a digital frequency synthesizer; 5. a heat sink; 6. and (3) a bracket.
Detailed Description
The invention is described in further detail below with reference to the drawings and examples. It is to be understood that the specific embodiments described herein are merely illustrative of the invention and are not limiting thereof. It should be further noted that, for convenience of description, only some, but not all of the structures related to the present invention are shown in the drawings.
The invention mainly comprises the following steps: in order to overcome the defect that the traditional single-piece acousto-optic deflector can only reduce the electrode length to improve the acoustic divergence angle and the ultrasonic utilization rate when improving the frequency bandwidth, the DDS digital frequency synthesizer is utilized to prepare the phased array acousto-optic deflector, so that the improvement is realized; by using the KYW crystal as the acousto-optic crystal, two different sound wave directions of the KYW crystal when the KYW crystal is used as the acousto-optic crystal and products and effects prepared correspondingly are researched, and under the condition that the damage threshold is basically unchanged, the acousto-optic figure of merit is improved, the using range of polarized light is widened, the radio frequency power is reduced, and the scanning angle is improved.
Referring specifically to fig. 1, 5, there is shown a phased array acousto-optic deflector using KWY crystals according to the present invention, comprising a KYW crystal 1 and a plurality of planar phased array units, each comprising a piezoelectric transducer 2, a matching network 3 and a digital frequency synthesizer DDS4 matched to each other,
wherein the crystal is formed in a KYW crystal (potassium yttrium tungstate, KY (WO) 4 ) 2 ) The piezoelectric transducers 2 are connected with the KYW crystal 1 through a bonding layer 9, and each piezoelectric transducer 2 is connected with a matching network 3 through an electrode layer 8 in sequence and driven by a digital frequency synthesizer DDS 4;
the phase difference between the plurality of digital frequency synthesizers DDS4 is adjustable.
Wherein the electrode layer 8 is a high-purity gold film with the thickness of 100-500nm, and the bonding layer 9 is a high-purity indium film with the thickness of 200-600nm.
The matching network 3 is composed of capacitors, inductors, radio frequency cables, connectors, etc.
Referring to fig. 4, the phased array acousto-optic deflector achieves accurate ultrasonic tracking through phase shifting between planar phased array units. Wherein the transducer elements have a center-to-center spacing s and are driven by constant amplitude RF signals, the phase of each element increasingThe transducer converts the radio frequency signal into an acoustic signal, the acoustic wave generated by each element being +.>Radian is different, phase->May be altered by an electrical signal. This variation causes the equiphase plane of the ultrasonic waves emitted by the array to be tilted at an angle θ relative to the plane of the transducer c Can be represented by formula->Determining, wherein K a Is the number of sound waves, V c Is the sound velocity, f c Is the frequency.
Setting θ i For the angle of the incident light to the plane of the transducer,the included angle between the incident light and the effective sound wave plane is defined, wherein k is the light wave number and Ka is the sound wave number; the angle error of perfect phase matching of ultrasonic tracking is:when matching exactly, the required error condition is ζ=0; phase->The method meets the following conditions:the phase shift required for each array element is a quadratic function of the radio frequency and each transducer requires precise phase control of the frequency according to a phase formula.
Therefore, the phased array transducer can be used for expanding the wide frequency band and reducing the driving power, the transducer can emit ultrasonic waves with the same frequency and different single phases, and the phase-shifted multiple sound fields are overlapped by interference to deflect an ultrasonic main lobe, so that the ultrasonic energy utilization rate is improved, and the Bragg phase matching is ensured in a wider frequency band.
Wherein the center distance between adjacent metal surface electrodes is represented by the formulaDetermining V c The sound velocity, f is the sound field frequency, and delta gamma is the ultrasonic tracking direction variation range in the bandwidth.
The design from the RF signal source to the piezoelectric transducer is centered at a fixed frequency f, and the transducer thickness is calculated by the formulaAnd (5) determining.
Referring to fig. 1 and 5, the piezoelectric crystal is an LN crystal, and the standing wave ratio in the LC impedance matching network is less than 1.2. The bottom of the KYW acousto-optic crystal is provided with a wedge angle for controlling sound absorption, for example, a wedge angle of 30 degrees, and roughening treatment is carried out, so that ultrasonic reflection deviates from an original path, and interference on an original effective sound field is avoided.
Further preferably, the wedge angles are double wedge angles respectively positioned on two mutually perpendicular surfaces of the acousto-optic crystal, so as to improve the anti-interference effect.
In order to further dissipate heat, a wedge-shaped heat dissipation block corresponding to the corresponding wedge angle can be adopted at the bottom of the acousto-optic crystal, and a heat dissipation block 5 is adopted at the side face to conduct heat dissipation.
The transparent glass is characterized in that an antireflection film 7 is further arranged on the transparent surface of the KYW crystal, and the antireflection film 7 is prepared from aluminum oxide, tantalum oxide and silicon oxide.
A bracket 6 is also arranged on the outer surface of the heat dissipation block 5 and the acousto-optic crystal 1 and is used for fixing the acousto-optic deflector.
Further, for the KYW acousto-optic crystal, as shown in fig. 2 and 3, the two acousto-optic directions have good quality. KYW crystal is monoclinic system of 2/m point group [100 ] of KYW]And [001]The monoclinic angle between the axes is equal to 94 deg., has a significant anisotropy, at the principal axis N of the optical permittivity tensor m 、N g And N p Analysis of acoustic characteristics on the associated coordinate axes, N p The axis is parallel to the second order symmetry axis of the crystal [010 ]]，N m Shaft and [100 ]]The axes forming an angle of 13.5 °, N g Shaft and [001 ]]The axes form an angle of 17.5 °.
The acoustic-optical characteristics of the KYW crystal are characterized by the elastic constant and the photoelastic constant related to the acoustic wave propagation, and the elastic constant can influence parameters such as the speed, the polarization direction, the attenuation and the like of the acoustic wave in the crystal; the photoelastic coefficient can represent the corresponding change of mechanical stress such as the change of the refractive index of the crystal on the optical characteristic; the elastic constants of KYW crystals are shown in table 1, and generally expressed as 6×6 tensor matrices for different propagation directions of acoustic waves in the crystals.
Table 1: KYW elastic constant
The photoelastic coefficients shown in table 2 were obtained from the optical characteristic changes.
Table 2: KYW crystal photoelastic coefficient
The analysis results in two effective directions for the KYW crystals.
I.e. acoustic wave edge N g Direction propagation and acoustic wave propagation along N g -30 ° directional propagation. When the sound wave is along N g The sound longitudinal wave is selected for directional propagation, and the sound-light figure of merit is M 2 ＝11×10 -15 S 3 Kg; based on similar elastic light coefficient P 13 And P 33 So that the use of the acousto-optic modulator is not affected by the polarization state of the light. When the sound wave is along N g -30 DEG direction propagation, selecting acoustic shear wave, obtaining maximum acousto-optic figure of merit M 2 ＝15×10 -15 S 3 /Kg。
Longitudinal acoustic wave along N g When the axis propagates, the diffraction efficiency of the horizontally polarized light is equivalent to that of the vertically polarized light; shear wave edge N g When propagating in the direction of 30 degrees, the incident light is horizontally polarized light.
The following examples illustrate the invention in its details:
embodiment one:
in this embodiment, KYW crystals are selected along N g The piezoelectric transducer uses an x-cut lithium niobate crystal, has a large electromechanical coupling coefficient, is used for generating shear waves, and is connected with the KYW crystal by a bonding layer vacuum cold pressure welding mode.
The central frequency of the acousto-optic deflector is 100MHz, the 3dB bandwidth is 50M-150Mhz, the wavelength of light is 1064nm, and compared with the traditional single-piece KYW acousto-optic deflector, the bandwidth performance is improved by about 60%. The sound velocity in the crystal is 2500M/s, and the sound-light optimal value is M 2 ＝15×10 -15 S 3 Kg; the characteristic length is 0.9mm, the center distance s of the adjacent transducers is calculated to be about 3mm according to the center distance formula of the adjacent metal surface electrodes, and the electrode distance of the adjacent transducers are calculatedThe ratio of the center distance is about 1:20-3:10, the ratio of the length of the single-chip electrode to the center distance is about 7:10-19:20, and the size of the single-chip electrode is 2.7mm.
Taking the influence of factors such as power and aperture of actual use of the product into consideration, the method is characterized by the formulaThe total electrode length and the number of transducer sheets are determined, the radio frequency power is used at about 7W, the aperture is 2mm, the number of transducers is 4 sheets, the total electrode length is 10.8mm, and the total electrode length is 12 times of the characteristic length.
In the embodiment, 4 transducers with the length of 2.7mm are used, and only 7W of radio frequency power is used under the caliber of 2mm, so that the acousto-optic deflector of the KYW crystal reaches the 3dB bandwidth of 100Mhz, the scanning angle can reach 42.6mrad, the scanning angle is equivalent to the damage threshold of the traditional quartz and fused quartz high-power laser crystal, and the scanning angle reaches 2GW/cm under the pulse laser of 1064nm of 10ns and 10MHz 2 。
Embodiment two:
in the embodiment, the KYW crystal adopts acoustic longitudinal wave propagating along the Ng direction, and the piezoelectric transducer is connected with the KYW crystal by a bonding layer vacuum cold-welding mode by using 36-Y tangential lithium niobate crystal to generate quasi-longitudinal acoustic wave.
The central frequency of the acousto-optic deflector is 200MHz, the 3dB bandwidth is 100Mhz, the wavelength of light is 1064nm, and compared with the traditional single-piece KYW acousto-optic deflector, the bandwidth performance is improved by about 60%; the sound velocity in the crystal is 4560M/s, and the sound-light figure of merit is M 2 ＝11×10 -15 S 3 Kg; the characteristic length is 0.9mm, the center distance s of the adjacent transducer is calculated to be about 3.5mm according to the center distance formula of the adjacent metal surface electrode, the ratio of the distance between the adjacent transducer electrodes to the center distance is about 1:20-3:10, the ratio of the length of the single-chip electrode to the center distance is about 7:10-19:20, and the size of the single-chip electrode is 3.2mm.
Taking the influence of factors such as power and aperture of actual use of the product into consideration, the method is characterized by the formulaDetermining total electrode length and transducer countWhen the radio frequency power is about 8W and the aperture is 2mm, the number of the transducers is 4, and the total electrode length is 12.8mm, which is 14.2 times of the characteristic length.
In the embodiment, 4 transducers with the length of 3.2mm are used, and only 8W of radio frequency power is used under the caliber of 2mm, so that the acousto-optic deflector of the KYW crystal reaches the 3dB bandwidth of 100Mhz, the scanning angle can reach 24.4mrad, and the problem that the polarization state of the thermoluminescent light is limited by the conventional acousto-optic crystal can be solved.
Compared with the traditional quartz material, tellurium oxide material and other acousto-optic media, the polarization state of the incident light required by the traditional material is fixed horizontal linear polarized light or vertical linear polarized light, and the acousto-optic crystal of the embodiment is not influenced by the polarization state of the incident light, so that the use scene is effectively enlarged; and the acousto-optic figure of merit of the KYW crystal in the longitudinal acoustic wave mode can reach 5 times of that of quartz material.
Comparative examples:
in the embodiment, the acousto-optic medium is quartz crystal, the sound field propagates along the x axis, and the acoustic wave mode is longitudinal acoustic wave; the piezoelectric transducer is connected with the quartz crystal by using 36-Y tangential lithium niobate crystal through a bonding layer vacuum cold pressure welding mode; the piezoelectric transducer does not use four-piece array unit transducers, but a conventional single-piece transducer structure; the same design is applicable to a 1064nm laser source with a 2mm light spot size.
The comparative examples have the following four disadvantages with respect to the examples of the present invention:
(1) The sound and light figure of merit is small: acousto-optic figure of merit M for quartz products 2 ＝11×10 -15 S 3 and/Kg, lower than KYW crystal.
(2) Polarization state limited: the polarization state of the incident light of the comparative example can be only linearly polarized light perpendicular to the product base, and the second example can be incident light of any linear polarization state.
(3) The scanning angle is small: an acousto-optic deflector with a 3dB bandwidth of 100MHz is also realized, the scanning angle of the first example can reach 42.6mrad, the scanning angle of the second example can reach 24.4mrad, and the quartz product of the comparative example only has 18.5mrad.
(4) The power is high: the characteristic length of the comparison example under the center frequency of 200MHz is 1.2mm, if the 3dB bandwidth of 100Mhz of the monolithic transducer structure is to be achieved, the transducer length can only be 4.3mm, compared with the invention, the length of the used electrode is greatly shortened, the radio frequency power of more than 50W is needed to be used, the same bandwidth is achieved, and the radio frequency power of less than 10W is needed for the first embodiment and the second embodiment of the embodiment.
In summary, the invention has the following advantages:
1. the invention uses KYW crystal as acousto-optic medium of acousto-optic deflector, the damage threshold can reach 2GW/cm 2 (10 ns,10MHz,1064nm pulse laser), which is equivalent to quartz material, the acousto-optic figure of merit is 7 times that of quartz material, M 2 ＝15×10 -15 S 3 The sound and light performance of the material is far better than that of quartz materials.
2. The invention increases the length of the used electrode, can effectively reduce the radio frequency power, increases the scanning angle, and is more suitable for the field of infrared and far infrared high-power long-wave laser modulation.
3. The multi-array unit phase-shifting transducer and the DDS signal source are used, so that phase-shifting ultrasonic wave coherent superposition is performed, ultrasonic tracking is completed, bragg loss is reduced, ultrasonic energy utilization rate is improved, and compared with a traditional single-chip acousto-optic deflector, bandwidth and dynamic scanning range are effectively enlarged; the frequency, the phase and the amplitude of each array unit can be precisely controlled by a computer system, so that the ultrasonic direction meeting the phase matching is tracked, and the tracking error is reduced.
While the invention has been described in detail in connection with specific preferred embodiments thereof, it is not to be construed as limited thereto, but rather as a result of a simple deduction or substitution by a person having ordinary skill in the art without departing from the spirit of the invention, which is to be construed as falling within the scope of the invention defined by the appended claims.
Claims (10)
1. A phased array acousto-optic deflector using KWY crystals, characterized by:
comprising a KYW crystal and a plurality of planar phased array units, each planar phased array unit comprises a piezoelectric transducer, a matching network and a digital frequency synthesizer DDS which are matched with each other,
the method comprises the steps that a plurality of piezoelectric transducers are arranged on a KYW crystal, the piezoelectric transducers are connected with the KYW crystal through bonding layers, and each piezoelectric transducer is connected with a matching network through an electrode layer in sequence and driven through a digital frequency synthesizer DDS;
the phase difference between the plurality of digital frequency synthesizers DDS is adjustable.
2. The phased array acousto-optic deflector of claim 1, wherein:
in the KYW crystal, the acoustic wave is along N g -30 DEG direction propagation, the acousto-optic optimum value is M 2 ＝15×10 -15 S 3 /Kg。
3. The phased array acousto-optic deflector of claim 1, wherein:
the piezoelectric transducer uses an x-cut lithium niobate crystal, and the sound velocity in the crystal is 2500m/s.
4. The phased array acousto-optic deflector of claim 1, wherein:
the number of the piezoelectric transducers is 4, the center distance s between adjacent transducers is about 3mm, the length of each electrode layer is 2.7mm, and the total electrode length is 10.8mm.
5. The phased array acousto-optic deflector of claim 1, wherein:
in the KYW crystal, the acoustic wave is along N g Direction propagation, sound-light optimum value at M 2 ＝11×10 -15 S 3 /Kg。
6. The phased array acousto-optic deflector of claim 5, wherein:
the piezoelectric transducer uses 36-Y tangential lithium niobate crystal, and sound velocity in the crystal is 4560m/s.
7. The phased array acousto-optic deflector of claim 6, wherein:
the number of the piezoelectric transducers is 4, the center distance s between adjacent transducers is about 3.5mm, the length of each electrode layer is 2mm, and the total electrode length is 12.8mm.
8. The phased array acousto-optic deflector of any one of claims 2-7, wherein:
the piezoelectric crystal is LN crystal, and standing wave ratio in the LC impedance matching network is less than 1.2.
9. The phased array acousto-optic deflector of claim 8, wherein:
the electrode layer is a gold film with the thickness of 100-500nm, the bonding layer is an indium film with the thickness of 200-600nm.
10. The phased array acousto-optic deflector of claim 1, wherein:
the bottom of the KYW acousto-optic crystal is provided with a wedge angle of 30 degrees for controlling acoustic absorption, and roughening treatment is carried out;
the bottom of the KYW acousto-optic crystal adopts a wedge-shaped heat dissipation block corresponding to the corresponding wedge angle, and the side surface adopts a main heat dissipation block to conduct heat dissipation; the transparent surface of the KYW crystal is also provided with an antireflection film.
Priority Applications (1)
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| CN202311476194.8A CN117724278A (en) | 2023-11-07 | 2023-11-07 | Phased array acousto-optic deflector using KYW crystal |
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