Large Nonlinear Phase Shifts in a Nitrobenzene-Cored Single-mode Fibre

Abstract

The availability of picosecond mode-locked pulses and low loss optical fibre has made it desirable to use the effects of self-induced phase-shifts for applications in all optical processing. There have been several successful demonstrations of all-optical switching in fused silica fibres in recent years. What is common amongst most of these devices is that they use long lengths of fibre, typically 25m to km, high optical powers or both. No demonstration of all optical switching in short lengths of optical fibre at relatively low powers has so far been demonstrated. This limitation is mainly due to the low nonlinearity of silica (3 x 10-20 m2/W). Recently, 29cm long fibres made with new glasses have been reported which yield 17π nonlinear phaseshift with an input power of 1kW [1]. This paper reports on the observation of self-induced polarisation instabilities in 10cm lengths of nitrobenzene-filled silica-capillary single-mode waveguides. Large phase changes of at least 12π are reported at peak input powers of only 14W, with no saturation of the nonlinearity.