R. Danielius et al., TRAVELING-WAVE PARAMETRIC GENERATION OF WIDELY TUNABLE, HIGHLY COHERENT FEMTOSECOND LIGHT-PULSES, Journal of the Optical Society of America. B, Optical physics, 10(11), 1993, pp. 2222-2232
We report on the generation of ultrashort tunable pulses with a cavity
less traveling-wave scheme consisting of a parametric superfluorescenc
e seed source and a parametric amplifier. We show that the traveling-w
ave approach, with its advantages of simplicity and direct generation
of tunable energetic single pulses, can be used in the femtosecond reg
ime, and to this end we discuss the performances that were obtained wi
th pump pulses of almost-equal-to 1-ps and 200-fs duration at waveleng
ths of 0.53 and 0.6 mum, respectively. Of particular interest is the b
eta-barium borate-based traveling-wave parametric generator (type-II p
hase matching), since it offers the possibility of generating nearly t
ransform-limited pulses that are continuously tunable within a wide sp
ectral range to as high as 3 mum in the IR. With a diffraction-limited
pump at 0.53 mum we obtained tunable pulses in a 1.2 X diffraction-li
mited beam, which could be focused, with an f/20 optics lens, to an in
tensity of 10(13) GW/cm2. A temperature-tuned lithium triborate-based
femtosecond parametric generator, with its smaller group-velocity disp
ersion and absence of walk-off, can operate at a pump energy of as low
as 30 muJ in a 200-fs pulse.