Optical Limiting Within Capillary Waveguides

Abstract

Abstract : A study of the optical limiting characteristics of capillary waveguides containing highly nonlinear cores is reported. Nonlinear waveguides prove useful, both for the study of fundamental physical phenomena they display and for practical applications (such as optical limiting) they may fulfill. Work presented here strives to use nonlinear waveguides as optical limiting elements, incorporating the waveguides into geometries that may integrate into modern optical fiber systems. Multi-mode and single-mode nonlinear waveguides, with core diameters ranging from 3.2 to 200 micrometers, were filled with solutions of silicon naphthalocyanine (SiNc). SiNc displays large absorptive and refractive index nonlinearity. The transmission characteristics of these nonlinear waveguides were measured as a function of incident energy from two different pulsed, frequency-doubled Nd:YAG lasers (producing 7 ns and 5 ns pulses at 532 nm). For the multimode waveguides, nonlinear effects are observed at input energies as low as 1.0 x 10(exp -10) J and a transmission of 5% or less was observed for input energies as low as 1.0 x 10(exp -7) J. For the single-mode waveguide, a limiting response was stimulated at input pulse energies < 20 pJ. Multi-mode waveguide data were compared with a three-level sequential absorption model, which modeled the nonlinear behavior of SiNc.