Photoinduced Optical and Electrical High-Voltage Pulsations and Pattern Formation in Photorefractive Crystals

Abstract

We review our results on conversion of CW laser Ar-ion beam power into pulsating multi-channel outputs: optical, electric and piezoelectric with simultaneous dynamic pattern formation. We show, that electrical pulsations generate high-voltage signals that may be used as a driving voltage for the conventional electro-optical modulator. We have also demonstrated the possibility of synchronization of two optical pulsators, through regulated optical coupling in a photorefractive LiNbO3 crystal. Spatial distribution of scattered light is self-organized in different patterns (hexagonal and cross-type).

Voltage pulsations in photogalvanic crystals as power supply for EO modulator

“…Electrical pulses from this photogalvanic pulsator were observed with maximal up to 100V as registered by oscilloscope Tektronix TDS 30-32D with 1 MΩ input. Electrical pulses had similar temporal shape as in our previous experiments with coherent (laser) illumination [7][8][9]: front pulse edge rise in nanoseconds with decay in microseconds. Depending on the connecting cable length we have observed different types of decaying periodic oscillations that follow initial electrical pulses.…”

“…Impressive self-organized optical patterns were pulsating in phase with high voltage pulses in the internal circuits [7,8]. In addition we have observed also radio-frequency signals, emitted from the crystals and picked up by the radio receiver, placed near the crystal.…”

“…In our experiments [7], optical and electrical pulsations were reported during CW illumination of z-cut crystals of Fe doped LN. Impressive self-organized optical patterns were pulsating in phase with high voltage pulses in the internal circuits [7,8].…”

Smart photogalvanic running-grating interferometer

“…This mechanical motion of the macroscopic LN crystal ͑weight is 0.47 g͒ was actuated by the low-power solid-state cw laser ͑P = 100 mW , = 532 nm͒. 3 The interference pattern motion is subsequently actuated by the photogalvanic electric field. Experimentally detected voltage and current pulsations have a saw-tooth shape.…”

Photo-magnetism and possible optical switching in Fe3+: PMN-PT: A Photo-EPR investigation

“…Light induced charge transport would result in selective changes of valence states of ions involved, thereby its magnetic state,, which can be monitored by electron paramagnetic resonance (EPR) spectroscopy. EPR is a highly sensitive nondestructive microwave spectroscopic method of identifying the magnetic state and chemical structure at a concentration level of a few tens to few hundreds of ppm of paramagnetic ions/radicals [7]. EPR measurements conducted with in situ optical illumination which give real time magnetic responses of the sample are described as photo-EPR measurements.…”