A 0.5 Terawatt, 125 Femtosecond Ti:Sapphire Laser

Abstract

Broadband, high-energy storage, solid state amplifiers and chirped-pulse amplification further extend the peak power obtainable from a laser source. Laser-generation of x-rays and strong-field experiments require focusable beams at terawatt power levels. We have constructed a system at 802 nm using Ti:sapphire amplifiers and the technique of chirped-pulse amplification. In our system, a dye laser produces a train of 85 fsec seed pulses. A positively-dispersive grating pair expander chirps these pulses, stretching the pulsewidth to 180 psec while preserving the femtosecond bandwidth. The stretched pulses seed a Ti:sapphire regenerative amplifier, producing 8 mJ, 180 psec output. Further amplification in a triple-passed Ti:sapphire amplifier increases the pulse energy to 120 mJ. A negatively-dispersive parallel grating pair removes the chirp, recompressing the pulse to 125 fsec. The final output contains 60 mJ of energy in a 125 fsec pulsewidth. The output beam is Gaussian and measured to be 1.2 times diffraction limited. Focusing with an f/6 lens achieves 87% transmission through a 10.8 micron pinhole. Hence, f/6 focusing will produce 1018W/cm2. Passage through a saturable absorber reduces the amplifier noise to signal power ratio to 10−9 in the leading edge of the short pulse, with a large signal, whole beam transmission of 70%. Both the regenerative and the final amplifier are pumped by the 532 nm frequency-doubled output of a single commercially available 10 Hz Nd:YAG laser.