Nonlinear Effects in Optical Fibers: Application to the Fabrication of Active and Passive Devices

Abstract

The development of high-quality low-loss optical fibers has resulted in the demonstration of several novel optical devices based on nonlinear effects that occur in silica fiber material. The successful operation of these devices has proven feasible in spite of the fact that the effective nonlinearity of silica is much smaller than materials commonly used in nonlinear optic experiments. The weak nonlinearity of silica is more than compensated by the capability of optical fiber to confine light to a small cross-sectional area without incurring damage and to maintain such confinement over large distances, resulting in high power densities in the fiber core and long interaction lengths. These favourable properties of optical fibers permit the observation of several different nonlinear effects. Stimulated Brillouin scattering (SBS), stimulated Raman scattering (SRS), and three-wave mixing have all been observed using both pulsed1, 2, 3 and continuous4, 5, 6 pump beams. Light induced birefringence in an optical fiber has also been detected. 7 More recently, a different type of nonlinear effect, light-induced refractive index changes in Ge-doped optical fiber has been discovered.8 Unlike the other nonlinearities in fiber the origin of this effect has not yet been established.