Abstract

We report the direct determination of the phase of femtosecond light pulses by spectrally resolved up-conversion. The correlation signal spectrum is recorded for different delays between the probed pulse to characterize and a reference one. The phase derivative of the probed pulse is then retrieved considering for each UV wavelength the delay for which its intensity is maximum (fig. 1). Basically this technique is a frequency sampling of the probed pulse and therefore needs a spectrally narrow reference beam. This is clearly seen in the case of linearly chirped gaussian pulses where solutions are found in closed form. The delay curve is then a straight line of equation, where Δω is the spectral full-width half-maximum of the studied pulse, Φ" its linear chirp, and τ is the delay between this pulse and the reference pulse of width δω and linear chirp ϕ".

© 1992 The Author(s)