Abstract

We first discuss the principally new effects of optical pulse frequency tuning and time delay (advancing) caused by two-pulse collision in a medium with cascaded quadratic nonlinearity. This phenomenon is a temporal analog of the cascaded beam refraction and reflection [1–3]. The mechanism of reflection can be explained as follows. In quadratic medium the weak signal pulse interacts with the power pump pulse on another frequency, and they generate the sum-frequency wave which due to cascading [4, 5] changes the refractive index at the signal frequency The kind of induced inhomogeneity depends on the sign of phase-mismatching between sum and signal waves, and the index change is proportional to the pump peak intensity. The total internal reflection of signal pulse from moving pump pulse can occur only in defocusing case. As a result of collision the group velocity mismatch sign alters and signal frequency changes. It means that signal pulse obtains a push, after which it moves away from the pump pulse with another velocity. If pump intensity is insufficient signal pulse outruns pump pulse and its frequency doesn’t change. In the case when pump pulse overtakes weak signal pulse the opposite effect of signal velocity growth can be observed.

© 2009 IEEE