Ti:sapphire/KrF hybrid laser system generating trains of subterawatt subpicosecond UV pulses
- P N Lebedev Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation)
The GARPUN-MTW Ti:sapphire/KrF hybrid laser system is used to investigate different multipass schemes for amplifying trains of ultrashort pulses (USPs) of subpicosecond duration. It is shown that, for an USP repetition period of 3 – 5 ns, which exceeds the gain-medium recovery time (∼2 ns), trains are amplified in the same way as single USPs. Due to this, a train can efficiently extract pump energy from the amplifier and sum energies of individual USPs. The energy of a four-USP train, extracted during four passes through the preamplifier and two passes through the final KrF amplifier (4 + 2 scheme), is saturated at a level of 1.6 J and corresponds to maximum USP peak powers of about 0.6 TW. The energy of amplified spontaneous emission (ASE), on the contrary, rapidly increases at a large total gain length L{sub eff} ≈ 6 m and is approximately equal to the USP energy. In the (4 + 1) and (2 + 2) schemes the USP energy decreases only slightly, to E{sub out} = 1.3 and 1.2 J, and the ASE fraction is reduced to about 10% and 3%, respectively. USP self-focusing leads to multiple laser beam filamentation and a 200-fold local increase in the radiation intensity in filaments, to ∼2 × 10{sup 11} W cm{sup -2}, a level at which the nonlinear loss in the output CaF{sub 2} windows of the KrF amplifier, caused by three-photon absorption, nonlinear scattering, and broadening of the radiation spectrum to a value exceeding the gain band of the KrF laser transition, becomes the main factor determining the saturation of the USP output energy. (lasers)
- OSTI ID:
- 22375911
- Journal Information:
- Quantum Electronics (Woodbury, N.Y.), Vol. 44, Issue 5; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1063-7818
- Country of Publication:
- United States
- Language:
- English
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