Influence of the nonunidirectional energy exchange on the polarization properties of the two-wave interaction in BTO crystal

Abstract

nal beam reflects from the mirror 3 and pass through the color filter 4 that ensures the intensity ratio Ip/Is -250. Both beams had the circular polarization after pass of the optically active analog of quote-wave plate 5. To obtain liner polarization with necessary angle @o relatively grating vector the polarizer 6 was used. The grating spacing h=Zn/II<I was equal to 1.86 pm. The intensity of the signal beam after crystal is measured by the photo diode 9. Polarizer 8 was used for measurement of changing polarization angle of the signal wave.In Refs.[1,21 is shown that contribution of the effect of self-diffraction gyration may be the reason of the nonunidirectional exchange a t the two wave mixing in a cubic photore-Our first experiment consisted of measurfractive crystal. In paper [3] authors experi-mixing gain for different mentally demonstrate the polarization angles ($0. The gain was deteI"ined from two ing the dependency of the two-wave coupling gain, when effective nonunidirectional energy exchange exists. But in all these papers the polarization dependency of the interaction effectiveness was considered. In this work we show that the above-mentioned effect also leads to a rotation of polarization of the signal (weak) wave. 3 4 5 6 7 n 4 Fig. 1. Experimental setup.In experiments we used the standard setup for symmetric two-wave mixing without an . external electric field (see Fig.l.), plane wave holograms were written in a Bi12Ti020 crystal 7 with beams from a He-Ne laser 1 (h, = 637 nm). Rotating the crystal around [ l l O ] direction we orient the grating vector K along [OOl], [ l l O ] or [lll] crystallographic axes. Semi-transparent mirror 2 splits beam from laser into two coherent beams. The sig-measurements of the signal beam intensity (without pump and then with pump) and was calculated as (1) where d = 6.93 mm is the crystal thickness along [110] axis.Rhombus in Fig.2 present the results of these measurements. In second experiment we determined the value of angle on that rotate the polarization plane of the signal wave when it passes through the crystal with pump (also for dsferent angles $0). For this we rotate the polarizer 8 to obtain a maximum intensity on photo diode 9 when is no pump in the crystal and then with pump. In both cases we registered angles on polarizer and calculated their differences A@ = $with pump -@without pump. Boxes in Fig-2 present the results of these measurements.In numerical calculations of the gain coefficient (see doted curves in Fig.2) we used expressions obtained in [2]. To generate these theoretical curves ru41, NA were used as free parameters to yield the best fit a t orientation of the grating vector along [OOil axis (see 1 r = 1," Is with Pump d i Is without pump Section II: Instrument Making 0-7803-6789-2/00/$10.00 OZOOO IEEE