V. M. Epikhin, L. L. Pal’tsev
- All-Russian Scientific Research Institute of Physical-Technical and Radiotechnical Measurements, Mendeleevo, Moscow region
Abstract: An acousto-optic modulator based on a TeO2 crystal for the frequency range 200–570 MHz with acoustic mode conversion upon reflection from the oblique face of the acousto-optic cell is fabricated and experimentally studied. The modulator operates with a collimated light beam ∼0.8 mm in diameter, and no beam focusing is required. For a sequence of control signal pulses at f > 250 MHz, a sharp (several times) reversible drop in the diffraction efficiency is observed within T1 = 3 – 20 μs after the onset of diffraction. The fall time front is shorter than 0.5 μs. The value of T1 depends on the control signal parameters. The upper limits of the frequency range of the modulator in the continuous regime and in the regime of a pulse train of the control signal are determined at 360 and 570 MHz, respectively. The attenuation coefficients of the transverse slow acoustic mode in TeO2 along the direction of its wave vector, which has an angle of inclination with the [110] axis of 16.80°, are measured: σ(360 MHz) = 1.8 ± 0.4 Np·cm-1, and σ(570 MHz) = 5.5 ± 0.8 Np·cm-1. The exponent in the frequency dependence σ(f) ∼ fn is estimated to be 2.4 ± 0.4. Possibilities and features of the TeO2 backscattering experiment are discussed based on the results obtained.