Abstract (Invited) |

**Acousto-Optic Cell Non-Linearity Fed by
Two-Frequency Acoustic Signal**

*V.Parygin, A.V.Vershoubskiy (Department
of Oscillation Physics, Faculty of Physics, Moscow State University, Moscow,
Russia)*

*e-mail:
parygin@osc162.phys.msu.su*

Acousto-optic
(AO) cell is the device that is linear relative to an optic signal and
non-linear relative to an acoustic signal. This non-linearity is associated
with the dependence of the diffracted light intensity on the acoustic wave
amplitude. As a first approximation this non-linearity may be approximated by a
cubic polynomial. In such approximation an optical beam diffracted by
two-frequency acoustic signal contains, besides two main maxima, two spurious
maxima that decrease the dynamic band of AO cell working as an acoustic signal
spectrum analyzer. The amplitudes distribution of main and spurious maxima is
analyzed in the work presented. It is shown that an appropriate preliminary
distortion of an input signal makes it possible to lessen the spurious maxima
level substantially. Moreover, the optimal coefficient of non-linear distortion
does not depend on the Bragg condition mismatch. The results testify that under
the condition of weak AO interaction the proposed distortion method allows to
increase the dynamic band of AO spectrum analyzer by 20 dB. However, if the AO
interaction efficiency is high, the preliminary distortion of an input signal
does not effect the dynamic band. Thus, the AO interaction non-linearity can be
compensated effectively in a wide range and improve the characteristics of an
AO spectrum analyzer.

Section
: 9