Dynamic-grating-assisted energy transfer between ultrashort laser pulses in lithium niobate.

Energy redistribution between two subpicosecond laser pulses of 2.5 eV photon energy is observed and studied in congruent, nominally undoped LiNbO, aiming to reveal the underlying coupling mechanisms. The dependences of pulse amplification on intensity, frequency detuning and pulse duration point to two different contributions of coupling, both based on self-diffraction from a recorded dynamic grating.

Interference and holography with femtosecond laser pulses of different colours.

Interferometry and holography are two domains that are based on observation and recording of interference fringes from two light beams. While the aim of the first technique is to reveal and map the phase difference of two wave fronts, the main task of the second technique is to reconstruct one of the two recording waves via diffraction of the other wave from the recorded fringe pattern (hologram). To create fringes, mutually coherent waves from the same laser are commonly used.

Secondary photorefractive centers in Sn2P2S6:Sb crystals.

Secondary photorefractive centers in Sb-doped Sn2P2S6 have a lifetime comparable to the formation time of the space-charge grating. This considerably affects the dynamics of two-beam coupling and results in a new type of transient gain enhancement for preilluminated samples.

Coupling of counterpropagating light beams in low-symmetry crystals.

Two-beam coupling gain enhancement is demonstrated for a nontraditional orientation of counterpropagating waves in the monoclinic crystal Sn2P2S6.

Double-phase conjugate mirror in nominally undoped Sn2P2S6.

Coherent oscillation is achieved in the geometry of a double-phase conjugate mirror in nominally undoped Sn2P2S6 with 647 nm radiation of a Kr+ laser. The specific temporal dynamics of oscillation with modulated intensity and periodic 0-pi-0-pi variations of the oscillation wave phase is similar to that observed earlier using a semilinear oscillator geometry. The described oscillator ensures submillisecond delay time in the appearance of the phase conjugate wave.

Four-wave-mixing coherent oscillator with frequency shifted feedback and misaligned pump waves.

The effect of the pump waves misalignment on the oscillation spectra and oscillation intensity of a semilinear photorefractive oscillator is studied numerically and compared with the results of the experiment performed with a KNbO3:Fe,Ag crystal.

Anisotropic diffraction from photorefractive gratings and Pockels tensor of Sn2P2S6.

The first observation of anisotropic diffraction and anisotropic self diffraction in low symmetry photorefractive crystal Sn(2)P(2)S(6) is reported. From comparison of the diffraction efficiency of isotropic and anisotropic diffraction the ratios of the Pockels tensor components are deduced, including some nondiagonal components that have never been evaluated until now. The particular orientation of the optical indicatrix in Sn(2)P(2)S(6) (roughly at 45 degrees to z- and x-axes at ambient temperature) has a paradoxical consequence: The efficiency of anisotropic diffraction depends solely on diagonal components of the Pockels tensor, while the efficiency of the isotropic diffraction is considerably affected by nondiagonal components.

Frequency-degenerate nonlinear light scattering in low-symmetry crystals.

A considerable distinction of light-induced scattering in optically biaxial crystals comes from the fact that the principal axes of the optical indicatrix do not coincide with the crystallographic directions. The study of photorefractive scattering in Sn2P2S6 (monoclinic symmetry) revealed the particular requirements as to light polarization for excitation of parametric scattering and the polarization inhomogeneity of wide-angle scattering.

Semilinear coherent optical oscillator with frequency shifted feedback.

It is shown that the saw-tooth variation of the cavity length in a photorefractive semilinear coherent oscillator can suppress the instability in the frequency domain and prevent a bifurcation in the oscillation spectrum. To achieve such a suppression the frequency of the cavity length modulation should be chosen appropriately. It depends on the photorefractive crystal parameters (electrooptic properties, photoconductivity, dimensions) and on the experimental conditions (pump intensity ratio, orientation of the pump and oscillation waves with respect to the crystallographic axes, polarization of the pump waves, etc.

Holographic solitons.

We propose a new kind of an optical spatial soliton: the holographic soliton. This soliton consists of two mutually coherent field components that interfere, induce a periodic change in the refractive index, and simultaneously are Bragg diffracted from the grating. Holographic solitons are formed when the broadening tendency of diffraction is balanced by phase modulation that is due to Bragg diffraction from the induced grating.