Amplified ultrafast optical switching by cascading cascaded second-order nonlinearities in a polarization-gate geometry

Abstract

We demonstrate amplified ultrafast all-optical switching of 250-fs pulses using two different types of cascaded second-order nonlinearities (CSNs) simultaneously in a simple polarization-gate geometry using a type II crystal. The first set of CSN processes has the effect of rotating the input-pulse polarization, yielding polarization gating. This signal pulse is then amplified by a second (different) set of CSN processes involving second-harmonic generation of the gate followed by a stimulated parametric down-conversion process. Using these “cascaded cascaded” second-order processes, we observe amplified switching with 320% efficiency and an on-off ratio of 6 × 10 5 in a 1-mm-thick crystal of BBO.