Abstract

A complex shaped ultrashort waveform whose time-dependent amplitude and phase can be arbitrarily specified is generated from a single incident femtosecond pulse by Fourier synthesis. In principle, waveforms with arbitrary shapes can be formed if both spectral phase and amplitude are properly manipulated. However, when the reduction in energy that necessarily accompanies amplitude manipulation is undesired, spectral phase-only manipulation is required. A proper phase-only mask that generates a specified waveform can be found by using numerical optimization techniques, such as simulated annealing (SA) algorithm, similar to those widely used to design filters for spatial beam shaping. However, some femtosecond waveforms generated by phase-onlv filters are very sensitive to variations in the input spectrum. Therefore, one must always redesign the phase-only mask through some iterative algorithms when the input spectrum varies. The process takes relatively long time.

© 1998 IEEE