GB1306428A - Arrangement for acousto-optical light deflection - Google Patents

Abstract

1306428 Deflecting light NIPPON TELEGRAPH & TELEPHONE PUBLIC CORP 23 Nov 1970 [21 Nov 1969(2) 24 Nov 1969(6)] 55583/70 Heading H4F An acousto-optical deflector comprises a single crystal of tellurium dioxide with the rutile structure (para-tellurite). Deflection of the light beam may occur by way of normal Bragg diffraction, in which the polarization of the incident and deflected light is identical, or via abnormal Bragg diffraction, which occurs for birefringent materials and in which the polarization of the deflected light is changed (see IEEE, J. Quantum Mechanics, QE-3, 1967, page 88), measurements of figures of merit M and M<SP>1</SP> are given for different acoustic and optical directions. L-mode acoustic waves have a relatively large velocity and therefore are useful for a rapid deflection system, whereas the S-mode wave in the [110] direction has a greater value of M and thus of deflection efficiency with a much reduced velocity. The S-wave in particular directions e.g. [1À38, 1, 0] has a zero temperature coefficient of velocity so that temperature variations do not affect the deflection angle. For two dimensional deflections, two deflectors may be arranged in tandem with mutually orthogonal acoustic propagation directions, or two transducers may be disposed on the same crystal to supply orthogonal waves thereto. In the former case a half wave plate may need to be inserted between the two devices. The use of differing types of acoustic absorbing materials is discussed, chalcogenide glasses such as arsenic selenide and sulphide being formed.