Two-wave and induced three-wave mixing on a thin Bi12TiO20 hologram

Петров, М. П.; Petrov, V. M.; Zouboulis, I.; Xu, Liangying

doi:10.1016/s0030-4018(96)00370-7

Cited by 12 publications

(5 citation statements)

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“…After the seminal paper of Petrov on adaptive holographic interferometry (AHI) [4], the possibility of using the dynamic holographic recording technique to achieve highly precise measurements of small displacements has been demonstrated in numerous systems [5]. Since then, AHI has been proved as a useful tool for measuring small vibration amplitudes of reflecting objects [6,7,8,9].…”

Section: Introductionmentioning

confidence: 99%

Adaptive Holography in Liquid Crystal Light-Valves

2012

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By performing two-wave mixing experiments in a liquid crystal light-valve, optical beam amplification is obtained as a strongly resonant process to which a narrow frequency bandwidth is associated. This property is exploited to realize adaptive holographic interferometric systems able to efficiently detect displacements as small as fraction of picometers. Pressure radiation induced deformations of a reflecting membrane are measured with the same type of system. Then, when used with complex wavefronts, like speckle fields, the LCLV-based interferometer allows to detect extremely small phase modulations. The examples shown demonstrate the potentialities of the light-valve for dynamic holography applications.

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Section: Introductionmentioning

confidence: 99%

Adaptive Holography in Liquid Crystal Light-Valves

2012

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“…For incident beams with comparable intensities, the modulation of the interference pattern is large, i.e., close to 1 and the phase grating induced in photorefractive crystals becomes inharmonic [48][49][50][51][52][53]. In this case, for dynamic photorefractive thin gratings, an additional mixing of diffraction orders produced by the grating harmonics may appear [54][55][56][57].…”

Section: Two-wave Mixingmentioning

confidence: 99%

“…In this case, the space-charge field distribution is harmonic, and the refractive index grating has the same spatial frequency and de-phasing of π/2 with respect to the fringe distribution [56,57].…”

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confidence: 99%

“…When E sc and the refractive index grating does not have the sinusoidal form of the incident interference pattern, i.e., for an inharmonic grating, the recording becomes nonlinear [56,57]. In this case, E sc has a spectrum of spatial harmonics with frequencies that are multiples of the incident pattern.…”

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confidence: 99%

“…Thus, the interference pattern in the photorefractive crystal produces the space charge electric field [56,57]:…”

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Dynamic Waveguides and Gratings in Photorefractive Crystals

Vlad

Fazio

Damzen

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Photo-Excited Processes, Diagnostics and Applications

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This chapter is an overview of the photorefractive effect, the important photorefractive nonlinear processes and common photorefractive materials. In Section 2, the formation of steadystate spatial solitons by laser beam propagation through photorefractive crystals (PRC) with optical activity and absorption is theoretically and experimentally described. The spatial soliton features, which characterize the dynamic waveguide built in PRC, are analyzed. The soliton polarisation dynamics reaches a stable behavior under high external electric fields. Two-wave mixing and self-diffraction in dynamic harmonic and inharmonic gratings, induced by lasers in PRC, are presented in Section 3. The diffraction efficiency and beam amplification can reach high values, with promising potential in optical interconnections and storage. Dynamic and adaptive gratings by double phase conjugation (DPC) in PRC are discussed in Section 4. High phase conjugated reflectivity, high coupling transmission efficiency and robust interconnections of mutually incoherent lasers are achieved in DPC using Rh:BaTiO 3 crystals. Overview of the photorefractive effect and materials Photoexcited processes in photorefractive crystals (PRC)The photorefractive effect is a process, in which the refractive index of an optical material is changed, when illuminated by light. The photorefractive effect is commonly understood by the band transport model [1][2][3][4][5][6][7][8]. According to this model, a photorefractive material contains deep and shallow levels in the forbidden bandgap due to impurities or defects in that material. In Figure 1, this model is illustrated for the case of a deep level associated with a donor and the shallow level-trap, to an acceptor. It is assumed that the donor concentration is greater than the acceptor, such as when the shallow acceptors are completely filled by electrons.It is also assumed that the donor level is deep in the bandgap and consequently, the thermal excitation is neglected.When the photorefractive material is illuminated by light with a high photon energy, the deep donors are photoionized and free carriers are raised into the conduction band. If additionally, nonuniform light distributions, such as focused laser beams or intensity interference patterns are used, the free electrons move into the conduction band by diffusion, drift and photovoltaic transport processes. Another important process in these materials is the recombination of the free carriers with CHAPTER 3

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