Observation of nonlinear optical transmission and switching phenomena in polydiacetylene-based directional couplers

Abstract
Nonlinear optical transmission and switching phenomena have been observed in directional coupler devices fabricated from soluble polydiacetylenes. Effects due to both slow thermal nonlinearities and ultrafast (picosecond) electronic nonlinearities were identified. At the operating wavelength of 1.06 μm used here, the ultrafast electronic nonlinear phenomena originated from intensity-dependent changes in the imaginary part of the refractive index due to two-photon absorption effects.