Experimental confirmation of the general solution to the multiple-phase-matching problem

We recently described a general solution to the phase-matching problem that arises when one wishes to perform an arbitrary number of nonlinear optical processes in a single medium [Phys. Rev. Lett. 95, 133901 (2005)]. Here we outline in detail the implementation of the solution for a one-dimensional photonic quasicrystal, which acts as a simultaneous frequency doubler for three independent optical beams. We confirm this solution experimentally using an electric-field poled KTiOPO4 crystal. In optimizing the device, we find— contrary to common practice—that simple duty cycles of 100% and 0% may yield the highest efficiencies, and we show that our device is more efficient than a comparable device based on periodic quasi-phase matching. © 2007 Optical Society of America OCIS codes: 190.2620, 190.4160, 190.4360.