Polarisation-independent electrooptical switch based on LiNbO3 and LiTaO3 crystals

Two electrooptical switches for nonpolarised narrow beams from fibre laser and luminescent sources are considered. Requirements for crystals, the accuracy of their thermal stabilisation, and tolerances for their manufacturing and adjustment are estimated from the point of view of the maximum switching contrast. A switch based on two LiNbO₃ crystals with a control half-wave voltage of ~270 V, connected with an isotropic single-mode fibre, is tested. It is shown that errors in the adjustment and manufacturing of crystal phase elements can be compensated by a weak controllable heating of one of the crystals.