Photorefractive two-wave mixing with focused Gaussian beams

Time evolution of Symmetry-forbidden Raman lines activated by photorefractivity

“…To analyze the dependence of the forbidden lines intensity upon time we realized a simulation code based on previous works by Wilson 27 and Fluck 28 . Essentially, the coupling phenomenon is enabled by a transfer of power between the ordinary (pump) and the extraordinary (generated) power mediated by the following occurrences: (i) a nonzero component of the photo-galvanic tensor which, upon the simultaneous presence of two orthogonally polarized beams with differing wavevectors, produces a spatially modulated current and in turn a space charge field (ii) a nonzero component of the electro-optic tensor, which transforms the spatially modulated field into a refractive index grating diffracting the pump beam into the generated one.…”

“…Equations (3 and 4) govern the space and time evolution of the coupling constant, as they are dependent on the beam intensities. Here we make substantial use of a “local” approximation which states that, for slowly varying intensities, the photorefractive equations for uniform illumination remain valid provided that intensity-dependent quantities are replaced by their local value 28 . Thus, the term in Eq.…”

A Simple Method for Photoconductivity Measurement in Lithium Niobate

“…Several solutions have been provided, ranging from the simple observation of the beam defocusing as a consequence of the optical damage either isotropically [9] or anisotropically [10], to the recording/erasing dynamic of photorefractive gratings [11][12][13][14][15]. However, both beam defocusing and holographic recording require a sophisticated modeling to obtain a robust estimate of the kinetics, especially when Gaussian beams are used, see, for example, [15][16][17]. Other approaches may be based on the recording kinetics of phase images [7], again taking advantage of the photorefractive effect.…”