Abstract

Nd:glass amplifiers have very good energy storage capabilities, but the energy extraction is extremely inefficient for short pulse amplification because of peak power limitations. These limitations can, however, be circumvented by frequency chirping and stretching the pulse prior to amplification. By amplifying the longer pulses, much higher energies can be achieved. After amplification, the pulse width is compressed to a value approximately equal to 1/Δf, where Δf is the total frequency chirp. To demonstrate this technique, we have produced picosecond pulses with energies in the tens of millijoules range.¹ A cw mode-locked Nd:YAG laser produces 100-ps pulses which are focused into a 2.4-km long single-mode optical fiber. At the output of the fiber, the pulses have been frequency chirped over a 3.5-nm bandwidth by self-phase modulation and stretched to 330 ps in duration by group velocity dispersion. The pulses are then amplified in a silicate glass regenerative amplifier to an energy of 2 mJ and further amplified to 50 mJ in a multipass system. The pulse width is then compressed to <2 ps by a double grating compressor which has an overall energy efficiency of 50 %.²

© 1986 Optical Society of America