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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