Tutorial-Spatio-temporal gcuo

www.physics.gatech.edu/frog Spatio-temporal pulse distortions Ultrashort laser pulses lead difficult lives. They’re routinely dispersed, stretched, amplified, and eventually compressed to, we hope, their shortest possible width. Whether from an oscillator, a regen, or a high-power amplifier, ultrashort pulses undergo massive manipulations to become so short. But at what price? Spatio-temporal distortions. Unless all the above devices are precisely aligned, the pulse will suffer from spatio-temporal distortions. The two most important and common spatio-temporal pulse distortions are spatial chirp and pulse-front tilt. A beam with spatial chirp has color varying spatially across the beam. A simple plane-parallel window will introduce spatial chirp if tilted. Fig. 1. Passage through a tilted window causes spatial chirp. This is simply due to Snell’s law. Pulse-front tilt is exactly what it sounds like. The very dispersion that is so useful for stretching and compressing pulses also causes pulse-front tilt (as well as spatial chirp) in the pulse if alignment of the stretcher or compressor is not perfect. In fact, pulse-front tilt can be shown to be equivalent to angular dispersion (a simple 2D Fourier transform shows this). The figures below show that dispersive elements, such as prisms and gratings, introduce these distortions. Fig. 2. Dispersive elements can yield both spatial chirp and pulse-front tilt. Pulse ...