Light diffraction by two parallel superposed ultrasonic waves of the frequency ratio 1:2.

The paper constitutes a concise study of light diffraction by two superposed ultrasonic waves of the frequency ratio 1:2, beyond the Raman-Nath diffraction regime. Relevant numerical simulations of light intensity distribution within separate diffraction orders are shown based on the Nth order approximation method (NOA). A comparison is given between generalized theoretical predictions (N=7) and simplified formulas of Mertens (N=2) [R. Mertens, Diffraction of light by two parallel superposed supersonic waves, one being the nth harmonic of the other: A critical study of the methods leading to approximate solutions in finite form, Proc. Indian Acad. Sci. 55 (1962) 63-98.]. Moreover, the results of the performed experiment are presented which indicate limited applicability range of Mertens' pioneer description of 1962.

Acousto-optic lens for pulsed lasers.

Theoretical predictions of the acousto-optic interaction under Raman-Nath conditions of ultrasound and laser light with a beam width w comparable to or smaller than the ultrasonic wavelength lambda are experimentally investigated, and good agreement between experiment and prediction is found. The experimental setup consists of a pulsed laser, emitting pulses that are synchronized with the sound frequency by means of a controllable delay time. When w approximately lambda, strong focusing is obtained for most delay times. The lensing properties of this configuration are carefully investigated.

Acousto-optic polarizer.

In the paper theoretical bases are presented, as well as their experimental verification, concerning an idea of a new type acousto-optic light ellipticity modulator, based on light diffraction phenomenon by ultrasonic waves, within the so-called intermediate diffraction regime. The experimental data obtained really good match relevant theoretical predictions, and the device examined enables a continuous light ellipticity variation from 0 up to 1, with low diffraction loses and for low electric voltage applied to ultrasonic transducer.

On the polarization of light diffracted by ultrasound

If light is diffracted by ultrasound in an isotropic medium with acoustically induced birefringence, the state of polarization is modified in each order of diffraction with respect to the initial state of polarization of the incident light wave. In the present paper, some polarization effects are discussed in the case of normal light incidence. In general a rotation of the main polarization plane occurs, together with a change of the ellipticity. However, while the former effect always takes place, the latter only occurs in the case of ultrasonic light diffraction of the intermediate type. Some experimental measurements are included in case of argon laser light being diffracted by an ultrasonic wave propagating in fused silica (SiO2).

Diffraction of light by two ultrasonic beams of frequency ratio 1:2, beyond the Raman-Nath diffraction regime

Light diffraction by two ultrasonic waves of frequency ratio 1:2 is examined beyond the Raman-Nath diffraction regime. Measurements were taken of +/- 1 order diffracted light intensities for some Raman-Nath parameter values, as a function of the phase shift between the sound beams. The experimental results obtained are discussed and compared with relevant theoretical predictions. Within the experimental conditions, a quite good quantitative agreement between the experimental data and the appropriate theoretical expectations is observed.