Distributed out-coupling of second harmonic generation in a waveguide via nonresonant first-order corrugation

In some waveguide materials, strong second-order optical nonlinearity is accompanied by strong harmonic propagation loss, particularly due to absorption. The conversion efficiency of such waveguides can be significantly enhanced by using a distributed out-coupling via a nonresonant first-order corrugation. Analysis of the proposed device is carried out using a coupled-mode approach. The results indicate that in certain cases, the second harmonic generation may be enhanced up to few orders of magnitude. The proposed scheme appears to be efficient mainly in phase-matched situations with moderate harmonic loss (up to about 100 cm^-1). The far field of the proposed surface emitting device is diffraction limited