AMPLIFIED ULTRAFAST OPTICAL SWITCHING BY CASCADING CASCADED 2ND-ORDERNONLINEARITIES IN A POLARIZATION-GATE GEOMETRY

We demonstrate amplified ultrafast all-optical switching of 250-fs pul ses using two different types of cascaded second-order nonlinearities (CSNs) simultaneously in a simple polarization-gate geometry using a t ype II crystal. The first set of CSN processes has the effect of rotat ing the input-pulse polarization. yielding polarization gating. This s ignal pulse is then amplified by a second (different) set of CSN proce sses involving second-harmonic generation of the gate followed by a st imulated parametric down-conversion process. Using these ''cascaded ca scaded'' second-order processes, we observe amplified switching with 3 20% efficiency and an on-off ratio of 6 x 10(5) in a 1-mm-thick crysta l of BBO. (C) 1997 Elsevier Science B.V.