Pulsed Excitation of Nonlinear Distributed Coupling Into ZnO optical guides

R. M. Fortenberry, G. Assanto, R. Moshrefzadeh, C.T. Seaton, and G.I. Stegeman

J. Opt. Soc. Am. B 5, 425-431 (1988)


Prism and grating coupling of high-energy laser pulses into thin-film ZnO waveguides has been investigated experimentally by using nanosecond and picosecond pulses. Large decreases in the coupling efficiency, angular shifts in the optimum coupling angle, and pulse distortion have all been observed with increasing pulse energy, primarily at 532 nm but also at 572 nm. Pulse probe experiments indicated an intensity-dependent refractive index with a nonlinearity turn-off time of 1 Ásec, in good agreement with calculations based on a thermal nonlinearity. The experimental observation were interpreted successfully in terms of a traveling-wave interaction between the incident and generated guided-wave fields for incident pulses of duration much shorter than the nonlinearity recovery time.