LAUSR

Abstract In this paper, a model of dual-beam nonlinear Fabry-Perot interferometer (DBNFPI) for laser Gaussian beam’s spatial modulation is proposed. It includes a thin film of oil red O sandwiched between two optical mirrors and is irradiated by two signal and pump laser Gaussian beams. The equation describing the output-input relation of intensities concerning pump intensity and the expression describing the spatial intensity distribution of output signal beam (OSB) are derived. The optical bistability of DBNFPI is numerically calculated with different pump intensities as well as the capability to spatially modulate the Gaussian beam is discussed. The different shapes of the OSB as: Gaussian, flat-top-Gaussian, ring-Gaussian, hollow-Gaussian, and multi-hollow-Gaussian are shown. The suitable range of pump intensity for particular shape of OSB is discussed, especially the hollow-Gaussian shape requirement for optically trapping microspheres having reflective index to be lower than that of embedding fluid.