J. Opt. Soc. Am. B, 16, 1592-1596 (1999).
We show the relevance of walk-off effects in pattern formation in a type-II optical parametric oscillator at frequency degeneracy. Neglecting walk-off, only phase patterns are formed and the intensity distribution is homogeneous. Walk-off changes the instability from absolute to convective for some parameter range. In the absolutely unstable regime, it induces for each polarization component of light a competition between two phase stripe patterns (traveling waves) with different wavelength. Phase stripe patterns at each of the wavelengths are equally likely to be selected and after a transient regime of coexistence, one of them takes over. In the convectively unstable regime we show the existence of intensity patterns sustained by noise. The patterns arise form the interference between traveling waves which are excited by noise and dynamically amplified
OCIS numbers: 190.4410 (Nonlinear optics, parametric processes), 190.4420 (Nonlinear optics, transverse effects in), 190.4970 (Parametric oscillators and amplifiers), 270.2500 (Fluctuations, relaxations, and noise).
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Pere Colet e-mail: [email protected] http://www.imedea.uib.es/~pere/