Photogalvanic pulsator

Summary form only given. We have observed regenerative photoinduced pulsations of optical and radio-frequency signals, generated by CW laser irradiation from Ar-ion laser in LiNbO/sub 3/:Fe. Pulsating optical scattering from the crystal has a distinct spatial structure in the form of expanding circular rings or bright crosses. Simultaneously, strong electromagnetic signals (EMS) are emitted from the crystal with bandwidth of about 1 GHz at 10% signal level. EMS was detected by an antenna-type electrode and analyzed by oscilloscope. We also have observed temporal modulation of the polarization state of cross-propagated signal beams at /spl lambda/ = 514 and 647 nm, synchronized with the EMS pulsations. Our explanation of the observed pulsations is based on self-organization of the photoinduced scattering into an array of reflection-type holographic gratings. Backscattering light waves combine with the forward pump wave, resulting in recording of the set of reflection electric-field gratings. The photogalvanic effect contributes to grating recording and creates a strong electric field along the optical axis about 50 kV/cm, which changes Bragg conditions for the holographic light scattering. This strong field also causes modulation of the probe signal laser beam due to modulation of birefringence by the electro-optic effect. As a result, strong space-charge waves are generated in the crystal, leading to the observed EMS picked-up by the antenna electrode.