Amplitude modulation of light by diffraction on Ba$_2$NaNb$_5$O$_{15}$ crystal domains

A study was made of the diffraction of light by a phase diffraction grating produced by an external electric field in crystals of barium sodium niobate having a periodic domain structure. It is demonstrated that such crystals are promising for making electrooptic diffraction light modulators. Hysteresis was discovered in the dependence of the diffracted light intensity on the strength of the applied electric field, and a hypothesis is put forward to explain this phenomenon. The results of measurements of $\varepsilon$ and $\tan\delta$ of polydomain barium sodium niobate crystals are given for frequencies up to 900 MHz.