V. V. Shkunov

Optical phase conjugation by microwatt power of reference waves via liquid crystal light valve

Abstract The operation of an LC light valve with a planarly orientated nematic cell with photosensible semiconductor layer is discussed using S-deformation near Frederiksz transition. Optical phase conjugation (OPC) of He-Cd laser radiation (λ=441.6 nm) with microwatt power is suggested and performed experimentally by the incident reference wave power P 1 ⩾10 -5 W. The diffraction efficiency of the hologram-valve in the direction of OPC-wave was ∼0.06 and the OPC fraction in reflected radiation was about 30–40%, the total nonlinear reflection factor being ∼10 -2 .

SBS wave front reversal for the depolarized light — Theory and experiment

Theoretical results concerning the wave front reversal (WFR) of spatially depolarized light in stimulated scattering are presented. The modes of scattering medium are found and the deterioration of reversal quality for the depolarized light is predicted. Experimental investigation of WFR in backward stimulated Brillouin scattering (SBS) in acetone was carried out when the light beam with λ = 1.06 μm was depolarized by the etched calcite plate. The share of scattered energy which has exactly reversed configuration, was measured. Experimental results quantitatively coincide with the theoretical conclusions.

Wave front reversal with angular tilting-theory and experiment for the four wave mixing

Abstract A scheme of wave front reversal in four wave mixing (WFR-FWM) with angular tilting of the reversed wave is proposed, theoretically discussed and experimentally realized. It is based on detuning from counterpropagation of reference waves. Unlike the proper WFR-FWM, tilting on the angle γ x reversal is effective only for the signal directions near the synchronism cone. when γ x ⪡ 1 this cone is almost the plane which is perpendicular to the turning direction, and the angular width of effective reversal across the plane is δθ x ∽ ( kL γ x ) -1 where L is the depth of the nonlinear medium, k = 2π/λ. The experimental investigation of the interaction of λ = 1.06 μm radiation with the saturable dye solution for the tilting angle γ x up to 10 -2 rad was carried out. The measured angular selectivity of tilting reversal corresponds to the theoretical one. The energetic fraction of an ideally reversed field in the whole reflected wave was quantitatively measured.

Recording and reconstruction of an object’s wave state of polarization by a volume hologram

The mode theory of transmission volume holograms is developed, taking into account the vector character of the electromagnetic field. In scalar recording media, eigenmodes are twice degenerated with reference to the state of polarization of the reconstructing field. Using this theory, the transformation laws of wave, with arbitrary spatially nonuniform field distribution and the state of polarization by a volume hologram are found. Two construction methods are detailed: (1) the reference beam has a wide angular spectrum, (2) the reference beam consists of two plane orthogonally polarized waves. In both cases the magnitudes of diffraction efficiency and polarization noise are calculated. Expressions obtained permit optimization of construction and reconstruction for both cases. In particular, we found the conditions on the reference beam for full reconstruction of the object field, including the whole structure of polarization.

Experimental observation of amplification of beams by dynamic surface holograms

Amplification of the power of a laser beam in the course of self-diffraction by a dynamic surface hologram was observed experimentally. The gain reached 14 without signal distortion. This self-diffraction was accompanied by a strong reduction in the pulse duration. A beam of high directionality was amplified by the transfer of energy from a reference wave which was of low optical quality. Wavefront reversal was performed by the hologram surface and this was accompanied by a sevenfold increase in the brightness.