Spatial coherence of an optical turbulent beam in a biased photorefractive crystal due to the spatiotemporal modulation instability

• Published in: Optics communications 2007-10, Vol.278 (1), p.187-193
• Main Authors: Sheu, Fang-Wen, Shih, Ming-Feng
• Format: Article
• Language: English
• Subjects: Beam trapping, self-focusing and defocusing; self-phase modulation; Coherence; Dynamics of nonlinear optical systems; optical instabilities, optical chaos and complexity, and optical spatio-temporal dynamics; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Interference; Nonlinear optics; Optical instabilities; Optics; Pattern formation; Physics; Self-focusing; Wave optics
• ISSN: 0030-4018; 1873-0310
• DOI: 10.1016/j.optcom.2007.06.002

We report the experimental observation of the dynamic pattern formation of a broad coherent light beam in a biased photorefractive crystal due to the spatiotemporal modulation instability. When the nonlinearity exceeds a specific threshold, the coherent light beam not only breaks up into light spots due to the modulation instability but also fast fluctuates both spatially and temporally, forming an optical turbulent beam, which behaves as a quasi-homogeneous speckled beam or a partially incoherent beam. We investigate the spatial coherence property of an optical turbulent beam from the visibility of the averaged double-slit interference fringe. We also numerically demonstrate the visibility variation of the instantaneous interference fringe of an optical turbulent beam.