Observations of self-steepening of an optical pulse in liquid-core optical fiber

Abstract

The possibility of self-steepening of an optical pulse has been studied theoretically, but so far no experimental result has been reported. As is well known, the self-steepening of a light pulse depends on the relationship of the refractive index of medium to the light intensity and the group velocity of light. Recently, using a liquid-core fiber system we observed the self-steepening effect. To observe this effect three conditions must be satisfied: (1) the interaction distance between light and medium must be long enough, (2) high input power is required, (3) the normal dispersion of the material can be neglected during the propagating process. In our experiment these conditions were satisfied. The liquid-core fiber filled with CS2 was 2 m long, the incident beam was the second harmonic of a Q-switched pulsed YAG laser (532 nm), and the linewidth of the pulse was 0.35 cm−1. When the input intensity was ~4 × 105 W/cm2 we observed that the trailing edge of the pulse steepened. The self-steepening became clearer if either the length of the fiber or the input intensity was increased.