All-optical polarization switch in a quadratic nonlinear photonic quasicrystal

We present an all-optical intensity-dependent polarization switch based on cascaded three-wave-mixing interactions in a quasiperiodic quadratic nonlinear photonic crystal. The polarization switching is realized by simultaneous quasiphase matching of upconversion and downconversion processes in LiNbO(3) and achieves three orders of magnitude better efficiency than previous devices based on cascaded cubic nonlinearities. The switch allows extending mode-cleaning and mode-locking techniques to considerably lower input power. We demonstrate experimentally that a single linearly polarized 1550 nm fundamental wave generates a new fundamental wave of orthogonal polarization.