Fig. 4-8 Operation of a 100 TW T-cube laser Amplifiers are photographed during laser-oscillation. The Ti:sapphire crystals (two red disks) are for the 10 TW amplifier (left) and for the 100 TW amplifier (right). On both sides of each crystal comes the laser radiation from the pumping all-solid-lasers (green YAG lasers).

Fig. 4-9 Measured shape for a 102 TW T-cube laser To measure the pulse shape of an ultrashort laser pulses, a fraction of an output pulse from a compressor is sent to an auto-correlator and then is superposed again to obtain the spectrum. The FWHM (full width at half maximum) of the measured pulse duration is 18.7 fs.

The development of high-peak-power, ultrashort pulsed lasers is a challenging task for world-wide laboratories aiming at an x-ray laser, a splendid light source in the future. We have achieved a compact Ti:sapphire laser system producing a peak power of 100 TW at 19-fs (femtoseconds) pulse duration and 10-Hz repetition rate, with a final goal of 1,000 TW. The result represents the highest peak power yet achieved in the world on a laboratory scale. A common approach is to employ the chirped-pulse amplification (CPA) technique. It consists of expansion of low-power ultrashort pulses for amplification followed by pulse compression in order to produce ultrahigh power, ultrashort laser pulses. The system is called a T-cube laser (Table-Top Terrawatt peak power laser). We also use the CPA technique for the Ti:sapphire laser system. A difficulty is that pulse duration shortening and power amplification are incompatible each other due to non-linear effects. The present result has been achieved by developing spectrum control techniques to suppress the pulse broadening in the laser materials. Key components developed are a green Nd:YAG laser with an energy of 7 J per pulse at 10 Hz for pumping, beam distortion-compensated Ti:sapphire crystals, a pulse expander to stretch 10-fs pulse duration more than 10,000 times, two amplifiers to get more than 109-fold powerful output, and a compressor to shorten again the pulse duration to one 10,000th.

Reference K. Yamakawa et al., Ultrahigh-Peak and High-Average Power Chirped-Pulse Amplification of Sub-20-fs Pulses with Ti:Sapphire Amplifiers, IEEE J. Sel. Top. Quantum Electron., 4 (2), 385 (1998).

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