Nonlinear liquid crystal optical fiber array for all-optical switching/limiting

Abstract

Liquid crystals in their various ordered and disordered phases have been shown to possess large optical nonlinearities over wide temporal and spectral ranges. Recent studies have shown that they can be used for optical sensor protection against short laser pulses throughout the visible range. In this paper, we report recent experimental results conducted with nanosecond and picosecond laser pulses. The centerpiece of the optical limiting/protection action is the liquid crystal fiber array which is positioned within an optical system such that its entrance plane coincides with an intermediate focal plane of the imaging system. The scenery from a large field of view is imaged onto an array area covering many (thousands) constituent fibers; on the other hand, a threat laser originating from a distant point source is brought to a focus spot size on the order of the diameter of a single constituent fiber. By optical waveguiding, the image is transmitted to the exit end. The liquid crystal fiber array will transmit low-power optical signal/scenery linearly and maximally; it will, via a variety of nonlinear mechanisms, limit the transmission of high energy laser pulses and therefore protect the downstream sensor.