FIBRE-GRATING PAIR PULSE COMPRESSION AT 1. 32 mu M.

The authors report on the power-dependent spectral broadening of the 85-ps pulses from a c. w. mode-locked Nd:YAG laser operating at 1. 32 mu m and the temporal compression of these pulses in a negatively dispersive delay line consisting of a pair of holographic gratings, to generate pulses as short as 1. 4 ps (a pulse compression of multiplied by 60). This temporal compression was associated with a pulse peak-power enhancement of approximately multiplied by 15. It is shown that a linear chirp exists over the major part of the spectrum of the pulse exciting the fibre, because compression takes place without evidence of any major wings on the compressed pulses. Any wings which are present and are not resolvable in the background noise of the authors collinear autocorrelation must have an intensity of less than one fiftieth of the peak of the compressed pulse. These picosecond pulses with high average power will find application in pulse propagation studies at the minimum dispersion wavelength of single-mode fibre and in Raman amplification studies.