The influence of laser radiation on X-ray diffraction in ferroelectric crystals with nonlinear optical properties

The influence of laser radiation (λ = 532, 630 nm) on X-ray diffraction in nonlinear ferroelectric LiNbO₃:Fe(0.01–0.02%) and triglycine sulfate (3C₂H₅NO₂.H₂O₄S) crystals has been studied. The laser radiation was applied to the sample on a four-circle X-ray diffractometer through a flexible optical fiber. The end of the light guide was fixed in a special attachment installed on the goniometer head and allowed the laser beam to be oriented along some chosen direction in a crystal and to maintain this orientation during the whole process of data collection over the reflection sphere. The output power of laser radiation at the end of the light guide was 7 to 10 mW (or about 0.3 W cm⁻²). The sample irradiation by laser light led to a visible increase of intensity for some reflections (up to 34%). A noticeable difference in the extinction parameters of the samples was found between the sets of reflections measured under normal conditions and those measured under laser irradiation.