Abstract

An analysis is made of an infrared chopper based on the refraction of light rays by a low frequency (~1-MHz) standing acoustic wave in a block of material such as germanium. Computer programs are described for tracing the rays through the acoustic field and for calculating the contrast ratio at a small aperture detector following the chopper. Experimental results obtained with a germanium device are in good agreement with the theory.

© 1981 Optical Society of America

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References

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  1. A. J. Demaria, G. G. Danielson, IEEE J. Quantum Electron. QE-2, 157 (1966).
    [CrossRef]

1966 (1)

A. J. Demaria, G. G. Danielson, IEEE J. Quantum Electron. QE-2, 157 (1966).
[CrossRef]

Danielson, G. G.

A. J. Demaria, G. G. Danielson, IEEE J. Quantum Electron. QE-2, 157 (1966).
[CrossRef]

Demaria, A. J.

A. J. Demaria, G. G. Danielson, IEEE J. Quantum Electron. QE-2, 157 (1966).
[CrossRef]

IEEE J. Quantum Electron. (1)

A. J. Demaria, G. G. Danielson, IEEE J. Quantum Electron. QE-2, 157 (1966).
[CrossRef]

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Figures (11)

Fig. 1
Fig. 1

Acoustooptic refractive modulator.

Fig. 2
Fig. 2

Two-phase acoustooptic refractive modulator.

Fig. 3
Fig. 3

The rf signals applied to two transducer sections.

Fig. 4
Fig. 4

Deviation of wave front by index gradient.

Fig. 5
Fig. 5

Focusing of rays after exiting chopper.

Fig. 6
Fig. 6

Germanium acoustooptic chopper mounted in heat sink.

Fig. 7
Fig. 7

Experimental setup to measure chopper characteristics.

Fig. 8
Fig. 8

Comparison of mechanically and acoustooptically chopped light. Sweep rate is 2 msec/div.

Fig. 9
Fig. 9

Variation of chopper repetition frequency and open/closed time ratio. Upper traces are detected light signal, and lower traces are rf excitation. Sweep rate is 2 msec/div. Open/closed time ratio: (a) 0.5; (b) 4; (c) 30; (d) 0.25.

Fig. 10
Fig. 10

Operation of chopper at high repetition frequencies. Upper traces are detected light signal, and lower traces are rf excitation. Sweep rate is 50 μsec/div. (a) Single pulse; (b) f = 10 kHz; (c) f = 20 kHz; (d) f = 10 kHz; on/off time complementary to (b).

Fig. 11
Fig. 11

Angular aperture of acoustooptic chopper.

Equations (9)

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Δ z = v t = c n + Δ n t
Δ θ 1 n 0 Δ z d n d x .
d n ( x ) d x = 2 π Λ sin ( 2 π x / Λ ) ,
Δ θ ( x ) = 2 π Δ n n 0 Λ sin ( 2 π x / Λ ) · Δ z .
x ( z ) = x 0 - 0 z θ ( z , x ) d z = x 0 - θ 0 z - 0 z Δ θ ( z , x ) d z ,
x ( z ) = x 0 - θ 0 z - ( 2 π Δ n n 0 Λ ) sin ( 2 π x / Λ ) 0 z z d z , θ ( z ) = θ 0 = 2 π Δ n n 0 Λ sin ( 2 π x / Λ ) 0 z d z .
P = 2 M 2 ( Δ n ) 2 ,
M 2 = p 2 n 6 ρ v a 3 ,
δ = [ Y / tan ( ϕ - θ e ) - F - R + Y / tan ϕ ] tan ( ϕ - θ e ) .

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