Ultra-powerful compact amplifiers for short laser pulses

Laser energies and powers, significantly much higher than available now through the most advanced chirped pulse amplifiers, might be achieved in much smaller devices. The working medium in such devices is plasma, capable of tolerating ultrahigh laser intensities within times shorter than it takes for filamentation instabilities to develop. The ultrafast amplification mechanism that outruns filamentation instabilities is the transient Raman backscattering of a laser pump in plasma. In principle, this mechanism is fast enough to reach nearly relativistic pumped pulse intensities, like 10¹⁷ W/cm² for λ = 1 μm wavelength radiation. Such a nonfocused intensity would be 10⁵ times higher than currently available. This mechanism also produces complete pump depletion. Many amplifiers with expensive and fragile meter-size gratings might then be replaced by a single amplifier comprised of a 1 cm size plasma layer. Raman instabilities of the pump to noise, as the pump traverses plasma layer towards the seed pulse, can be suppressed by detuning the resonance appropriately, even as the desired amplification process persists with high efficiency due to nonlinear resonance broadening. Moreover, since the peak intensity scales like 1/λ², even much higher laser intensities might become feasible when appropriate x-ray pump lasers are developed.