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Ac square-wave field-induced subharmonics in photorefractive sillenite: threshold for excitation by inclusion of higher harmonics

1999; Optica Publishing Group; Volume: 16; Issue: 1 Linguagem: Inglês

10.1364/josab.16.000103

1520-8540

Per Michael Johansen, H. B. Pedersen, Evgeny V. Podivilov, B. Sturman,

Photonic and Optical Devices

We investigated both analytically and numerically the simultaneous influence of higher-harmonic gratings and subharmonic gratings on the threshold for generation of the subharmonic K/2 grating. The higher-harmonic grating causes feedback to the fundamental grating, thus leading to a nonlinear correction in dissipation, and the threshold for subharmonic generation is substantially modified by the presence of more subharmonics. The numerical solution shows that the inclusion of five higher-harmonic components and four subharmonic components are sufficient to cover the entire spatial region. The discrepancy between the analytical and the numerical solution increases with increased electric-field amplitude.