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 0.42 - 5.5 TeO2 >2000 20 0.35 - 5 Glass 10 0.4 - 2.5 Germanium 600 - 800 5 100 - 150 2 - 20 TeO2 chirp ~2000 >20 0.35 - 5 Gap ~2000 1000 0.6 - 1 GaAs ~400 200 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
