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Photonics Handbook

Acousto-Optic Devices

Charts showing the characteristics of acousto-optic scanning devices, acousto-optic figures of merit, and solutions for common problems with acousto-optic processor devices.


ACOUSTO-OPTIC SCANNING DEVICES: CHARACTERISTICS

MODULATORS

              
Material      
Bandwidth     
   (MHz)
  Rise Time     
    (ns)
       Acousto
Input Power (W)     
   (Saturation)
     Material
Wavelength
Range (µm)
     
       Efficiency at
Maximum Bandwidth
          (633 nm)
                       
  Glass     5 - 10     50         1 - 6     0.4 - 25        >70%
  PbMoO4     >80     4 - 6         0.5 - 1.5     0.42 - 5.5        >70%
  TeO2     >80     4 - 6         0.5 - 1.5  
  0.35 - 5        >70%
  Germanium
    10     70         20 - 30
    2 - 20
        >50% at 10.6 µm
   GaP     100 - 1500

  10 - 0.7
        0.5 - 2     0.6 - 1
       >80%
  GaAs     50 - 200
  20 - 5
        0.5 - 2

  1 - 1.6        >30% at 1.5 µm

DEFLECTORS

                       
Type              
  Resolution           
  Scan Speed            
 (Spots/µs)
  Acoustic Power
         (W)
            
Wavelength Range
            (µm)
                   
  PbMoO4     >1500        15        <5          0.42 - 5.5
  TeO2     >2000        20        <5          0.35 - 5
  Glass     <1000        10        <5          0.4 - 2.5
  Germanium     600 - 800        5        100 - 150          2 - 20
  TeO2 chirp     ~2000        >20        <1 (avg.)          0.35 - 5
  Gap     ~2000        1000        <1          0.6 - 1
  GaAs     ~400        200        <1          1 - 1.6

ACOUSTO-OPTIC FIGURES OF MERIT

                       Material                Acoustic Mode            
  Figure of Merit (M2)
        (S3/kg)
             
Acoustic Velocity
       (mm/µs)
               
  Flint glass (SF 4)                  Longitudinal         4.51 x 10—15             3.63
  TeO2                  Longitudinal         34.5 x 10—15             4.2
  TeO2                  Shear          793 x 10—15             0.617
  PbMoO4                  Longitudinal         36.3 x 10—15             3.63
  GaP                  Long            30 x 10—15             6.32
  GaP                  Shear            16 x 10—15             4.13
  GaAs                  Long          104 x 10—15             5.15
  GaAs                  Shear            46 x 10—15             3.32


ACOUSTO-OPTIC PROCESSOR DEVICES:
PROBLEMS AND SOLUTIONS

         Problem  
 Cause                                                            
  Solution
  Limited bandwidth   Transducer impedance
mismatch
  Acoustic impedance matching (quarter-wave layers)
           
  Quadratic phase error       Quarter-wave matching, frequency plane phase filter
           
  Limited bandwidth   Acousto-optic interaction   Birefringent diffraction
Beam steering
           
  Frequency distortion/ frequency blurring   Acoustic dispersion   Increasing interaction length
(limited bandwidth)
Optical beam apodization
Increasing transducer height
Acoustic Beam apodization
Birefringent diffraction
Material selection
           
  Limited resolution
slide lobes
  Optical diffraction   Increasing aperture
Optical beam apodization
           
  Fresnel pattern distortion   Acoustic diffraction   Frequency plane filtering
Acoustic beam apodization
Material selection

Source: Isomet Corp. and Brimrose Corp. of America
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