A new approach to picosecond laser pulse analysis shaping and coding

An optical device exhibiting both a time versus frequency and a space versus frequency dispersion has made possible the performance of 1) the pulse by pulse spectrum analysis of mode-locked Nd-glass laser trains and 2) the shaping of these pulses by a completely passive process. The relatively poor performance of this spectrum analyzer (7 spectral lines resolved) is essentially due to the rise time of the photodetection setup utilized in the experiments. The shaping consists in a preliminary pulse expansion (from picoseconds to nanoseconds), which gives linear FM long pulses whose envelopes are then modulated with a rise time of 50 ps by a spectral filtering simply obtained by diaphragms and neutral filters.