Research Index / High-Field Technology / High-Field Ti:Sapphire Laser
The maximum laser energy which could be reached with Ti:sapphire lasers is limited by the saturation fluence and crystal size to values on the order of 100 Joules. It means that Petawatt-scale powers are possible if a pulse is compressed to ~30 fs. In comparison to the first Petawatt laser built on Nd:glass at Lawrence Livermore National Laboratory (LLNL), the Ti:sapphire Petawatt lasers will be much smaller in size, have much higher repetition rate and shorter pulse width. Currently only a few sub-100TW lasers are available worldwide.
We have developed a design of the first Ti:sapphire Petawatt scale laser. The part of the laser up to 100 TW was developed using supplementary MRI funding (NSF Major Research Instrumentation Program). Several challenges have to be met in order to built a laser to be used in high-field experiments. One of the most important yet unsolved problems in high-field development is reaching the high-contrast level. For a transparent dielectric target at an intensity 1019 W/cm2, a 108 contrast is needed to ensure that laser pulse interacts with a solid rather than with plasma created by the prepulses yet current lasers have contrast level between 105 and 107.
In the development of the CUOS 100-TW laser, we made two major contributions in solving the contrast problem - a high-energy regenerative amplifier and a saturable-absorber-based pulse cleaner. These contributions allowed us to reach 108 contrast - the highest published contrast value so far. One of them - the regenerative amplifier design - is currently being duplicated for the LLNL Falcon laser. Using a developed high-energy regenerative amplifier, a single-stage terawatt-power laser was also demonstrated.
The other major problem is preserving the temporal and spatial phase of the amplified pulse. A grating-mirror stretcher was developed to do this in a temporal domain. The stretcher allows dispersion compensation up to the fourth order and good quality pulse compression down to 28 fs. For spatial phase control we developed a cryogenically cooled 4-pass amplifier to eliminate thermally induced distortions.
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