Dynamic Denisyuk holograms in cubic photorefractive crystals

Abstract

Theoretical and experimental studies of the interaction of two counterpropagating light waves on dynamic reêection gratings formed in the Denisyuk scheme in cubic photorefractive crystals due to the diffusion mechanism of the charge transfer are considered. The results are presented which demonstrate the possibility of using dynamic photorefractive Denisyuk holograms to design adaptive elements of measuring systems based on optical and ébreoptic interferometers.

Contribution of the inverse flexoelectric effect to counterpropagating two-wave mixing of light beams in photorefractive crystals

“…1) in a photorefractive crystal causes a dynamic hologram to form in it, on which they are simultaneously selfdiffracted. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]19 This involves the interference of each of the transmitted beams with one of the diffracted beams-i.e., reference beam I P interferes with I S1 , and I S interferes with I P1 . The output intensity of the signal beam transmitted through the crystal is expressed as…”

“…In the absence of an external field, a significant photorefractive response can be achieved in electro-optic crystals with counterpropagating mixing of light waves on a volume reflective hologram formed using Densiyuk's layout. [8][9][10][11][12][13][14][15] One possible application of volume holograms in photorefractive crystals is a laser interferometer. [1][2][3][4][5][6][7]11,[14][15][16][17] Laser interferometers convert phase modulation of light into intensity modulation, and this allows the mechanical vibrations of surfaces that reflect or scatter the light beams to be measured with high accuracy.…”

“…The dynamic character of the holograms in photorefractive crystals, which have a finite response time when they are overwritten, makes it possible to carry out adaptive processing of nonsteady-state light-field patterns in laser interferometers, ensuring both effective phase demodulation and the compensation of the low-frequency modulation caused by the slow drift of the external conditions. Counterpropagating wave mixing, used in such crystals to form effective reflective holograms by a diffusion mechanism in the absence of applied external electric fields, [8][9][10][11][12][13][14][15][16][17] is attractive for adaptive laser interferometry.…”

“…[1][2][3] An important feature of reflective volume holograms recorded with wave mixing in the visible region is the small spatial period, which is about 100 nm. 1,3,[15][16][17] Such reflective holograms with high spatial frequency are characterized by electric-field gradients that can reach gigantic values, measured in TV∕m 2 . Because of the inverse flexoelectric effect, which causes the medium to exhibit elastic strains (elastic stresses) proportional to the gradient of the electric polarization (electric stress), [20][21][22] appreciable elastic strains can appear in the crystal that introduce an additional contribution to the photoelectric response of the medium because of the photoelectric effect.…”

Resonance Micro-Weighing of Sub-Picogram Mass with the Use of Adaptive Interferometer

“…Alternatively an interferometer can be implemented with use of dynamic hologram (DH) recorded in a photorefractive crystal (PRC). Due to adaptive properties of DH such an interferometer can stably operate in industrial environment and with light waves having complicated wavefronts [6,7].…”