Ultrashort Laser Pulse Phenomena, 2nd Edition

Problems 427

schemes (see for example DiTrapani et al. [54] and Wilhelm et al. [55]). Using

a noncollinear geometry extremely large amplification bandwidths have been

achieved, resulting in pulses as short as 4 fs after compression of the amplified

spectrum (continuum) [56].

Because optical parametric amplification is a nonresonant nonlinear optical

process the material does not absorb energy, and the heat load is considerably

smaller than in ordinary laser gain media. High gain factors can be achieved

at relatively small interaction lengths (single pass) which reduces the effect

of dispersion and nonlinear phase modulation on the pulse and beam profile.

Provided the gain bandwidth is large enough, gain narrowing, which limits

the bandwidth of pulses from ...