Abstract

INDRODUCTION Up to now the main interest in photorefraction is focused in the visible and recently in the infrared part of the spectrum. For certain application however, photorefraction in the UV seems of great promise. Only Fridkin et.al. [1] and Montemezzani et.al. [2] reported results in the Ultraviolet with KDP at deep temperatures and Bi4Ge3Oi2 at room temperature, respectively. Some years ago, Orlcwski et.al. [3 examined LiNbO3 and LiTO3 doped with transition metals in the UV. The hole conductivity was increased due to oxidization of the samples. Since hole conductivity does not contribute to the photovoltaic effect, diffusion became the dominant charge transport mechanism in strongly oxidized crystals. Very high absorption inhibited further sensible examinations. In a recent publication [5] we reported a small photovoltaic field of approx. 550 V/cm for nominally undoped LiNbO3- crystals with moderate absorption at 35lnm. The charge transport is dominated by diffusion of photoexcited holes. We extended our investigation to the spectral dependence of photoconductivity- and wave mixing- experiments. The unique results additionally make feasible self pumped phase conjugation with an external ring and self enhancement effects if beams are diffracted at fixed gratings. In all experiments extraordinary polarisation and grating vector parallel to the crystals c-axis were chosen . to address the largest electrooptical coefficient r33 in LiNbO3.

© 1993 Optical Society of America