Abstract
For Fe-doped lithium niobate crystal (LN : Fe 0.1 wt%) grown by Czochralski technique, the effects of oxidation and reduction state were investigated on the photoinduced birefringence change by Ar-laser irradiation (488.0 nm). (1) A high accuracy apparatus for the measurement of the birefringence has been developed (Sénarmont method). (2) In LN (undoped) the birefringence change is negligibly small (<10-6) regardless of the state of oxidation or reduction. (3) In LN : Fe the change is between 1.5 X 10-3 and 10-4. (4) It is possible to prepare a sample, 'oxidized LN : Fe', in which the change is still kept for long time even after stopping the irradiation.
