6533b7d1fe1ef96bd125d5e5

RESEARCH PRODUCT

Experimental approach to transverse wave-number selection in cavity nonlinear optics

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Spontaneous transverse pattern formation is experimentally studied in a ${\text{BaTiO}}_{3}$ photorefractive oscillator under degenerate four-wave mixing conditions. A near self-imaging resonator of high Fresnel number and quasi-one-dimensional in the transverse plane is used. A fine control technique of the cavity detuning, $\ensuremath{\Omega}$, is described. It allows a precise study of the relation of $\ensuremath{\Omega}$ with the transverse wave number ${k}_{\ensuremath{\perp}}$ of the roll patterns selected by the system. The law ${k}_{\ensuremath{\perp}}^{2}=\ensuremath{-}\ensuremath{\Omega}∕a$ is verified, which evidences that wave-number selection is mainly dictated by the cavity geometry. The experimentally obtained value of the diffraction parameter $a$ matches the theoretical prediction within the error intervals. The bifurcation diagram obtained by varying $\ensuremath{\Omega}$ shows homogeneous states and domain walls for positive $\ensuremath{\Omega}$, roll patterns for negative $\ensuremath{\Omega}$, and nonperiodic patterns for intermediate, negative detuning values. The latter are interpreted also in the frame of the cavity selection mechanism by taking into account the finesse of the cavity.