Blue and green Čerenkov-type second-harmonic generation in a polymeric Langmuir–Blodgett waveguide

Abstract

Blue (430-nm) and green (532-nm) wavelengths of Čerenkov radiation were generated in an all-polymeric Langmuir–Blodgett (LB) waveguide. A nonzero second-order nonlinear-optical (NLO) susceptibility was obtained by alternate deposition of an NLO active and an NLO passive polymer. The Čerenkov condition was fulfilled through control of the thickness of the LB film and the modal dispersion relations for waveguides. The second-harmonic light, generated in the waveguide, leaks into the substrate at the Čerenkov angle. The Čerenkov-type guided-mode-to-radiation-mode phase-matching scheme reduces the waveguide attenuation for the second harmonic and provides a convenient way of separating the second harmonic from the fundamental.