= A. Piskarskas
{c}
\b[A. Piskarskas] coauthored the 1992 demonstration of <optical parametric chirped pulse amplification> with <A. Dubietis> and <G. Jonušauskas>. The paper amplified chirped, stretched pulses in <beta barium borate> and reported compression to $70\,\mathrm{fs}$.<Powerful femtosecond pulse generation by chirped and stretched pulse parametric amplification in BBO crystal by A. Dubietis and others>[published byline and publisher Abstract]{ref}
The method combines two useful operations. A <chirp> correlates optical frequency with position within an <optical pulse>, permitting the pulse to be stretched before amplification and recompressed afterward. An <optical parametric amplifier> transfers energy from a pump wave to a signal and an idler through an interaction governed by <nonlinear optics>. Stretching limits the instantaneous signal intensity during amplification while leaving a route to short final duration.
For an original rectangular-pulse estimate, take <laser pulse energy> $E=1\,\mathrm{mJ}$. A duration of $100\,\mathrm{fs}$ gives $P=E/\tau=10\,\mathrm{GW}$, whereas stretching to $10\,\mathrm{ps}$ gives $100\,\mathrm{MW}$ at the same energy. The factor of 100 follows from the stipulated pulse shape and duration ratio. Real shaped pulses require the corresponding relation between <laser pulse energy>, <peak power> and <pulse duration>; amplification and recompression also introduce losses. These numbers illustrate the design principle, not the 1992 apparatus's energy or pump conditions.
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