Optical rectification in a traveling-wave geometry

We study the generation of microwave pulses due to optical rectification in a traveling-wave geometry. A system of evolution equations is derived whic h describes the mutual propagation of both optical and microwave fields. Ov erlap integrals and optimization criteria are given, and analytical express ions to determine the generated microwave pulse are derived. It is observed that in non-velocity-matched geometries two microwave pulses are generated initially. Both are the exact image of the optical signal. One pulse stays attached to the optical wave, while the other propagates at the microwave group velocity and is subject to absorption and dispersive broadening. In c ontrast, in velocity-matched configurations a single signal is generated wh ich is proportional to the first derivative of the optical pulse. It is fou nd that for increased conversion efficiencies;the action of the generated v oltage on the optical wave via the electro-optic effect can no longer be ne glected, and results in an effective cubic nonlinearity acting on the optic al wave. [S1050-2947(99)04011-1].