Ultrafast optical switching by use of fully phase-matched cascaded second-order nonlinearities in a polarization-gate geometry

We show that cascaded second-order nonlinear-optical processes can occur in a convenient polarization-gate beam geometry. Our arrangement uses typeII phase matching, and both individual second-order processes (upconversion and downconversion) are simultaneously phase matched. This geometry can be applied to efficient ultrafast optical switching. With a β-barium borate crystal and lightly focused 250-fs, 7.3-μJ pulses, we achieve a switching efficiency of 15% and an on endash off ratio of 3x104 on a pulse-length-limited time scale. copyright 1997 Optical Society of America