Abstract

We have developed a high intensity, ultra-short kilohertz laser system operating in the mid infrared, between 3 and 4.5 μm. The output of an ultrashort pulse oscillator (sync-pumped dye laser or mode-locked Ti:Sapphire laser), which is tunable about 800 nm, is amplified in a Ti:Sapphire regenerative amplifier, using chirped pulse amplification. Another pulse at λ=1053 nm, synchronized with the tunable pulse, is amplified in a cw pumped Nd:YLF regenerative amplifier. Mixing the two pulses in a nonlinear crystal, we obtain the difference frequency in the mid-infrared. A schematic of one configuration is shown in the figure below. The 800 nm oscillator in this case is a dye laser synchronously pumped by a mode-locked Nd:YLF laser, which also acts as the seed source for the 1053 nm light, thus providing optical synchronization between the two pulses at the mixing crystal. This configuration yields 1 psec pulses in the mid-infrared with an energy of 70 microjoules, which may be focussed, using f/4 optics, to peak intensities above 10¹² W/cm². The 1053 nm seed source may also be electronically synchronized with a mode-locked Ti:Sapphire oscillator in place of the dye laser, reducing the pulsewidth and increasing the peak intensity by an order of magnitude.

© 1997 Optical Society of America