A. Varanavicius

Highly efficient parametric conversion of femtosecond Ti:sapphire laser pulses at 1 kHz

Pulses with energies as high as 150 microJ and durations as low as 60 f(s) were generated from 1.1 to 2.6 microm by a traveling-wave parametric converter pumped by femtosecond pulses of a Ti:sapphire laser with chirped-pulse amplification.

Self-guided propagation of femtosecond light pulses in water

We report experimental evidence of self-guided propagation of femtosecond laser pulses in water. A light filament induced by 170-fs, 527-nm pulses has a diameter of 60 microm (at the 1/e2 level) and persists over a distance of 20 mm. The filamentary mode is sustained over a wide range of input power, and the energy excess is converted into conical emission. In the time domain, the pulse trapped in a filamentary mode experiences a number of splittings occurring in the early stage of filament formation.

Parametric generation of high-energy 14.5-fs light pulses at 1.5??µm

High-energy light pulses that are tunable from 1.1 to 2.6 mum, with a duration as short as 14.5 fs were generated in a type II phase-matching beta-BaB(2)O(4) traveling-wave parametric converter pumped by 18-fs pulses obtained from a Ti:sapphire laser with chirped-pulse amplification, followed by a hollow-fiber compressor.

Nonlinear space-time dynamics of ultrashort wave packets in water

We have monitored the space-time transformation of a 150-fs pulse undergoing self-focusing and filamentation in water, by means of the nonlinear gating technique. We have observed that pulse splitting and subsequent recombination apply to axial temporal intensity only, whereas the space-integrated pulse profile preserves its original shape.

NEAR-DEGENERATE CASCADED FOUR-WAVE MIXING IN AN OPTICAL PARAMETRIC AMPLIFIER

Efficient generation of new spectral components owing to second-order cascading in a seeded broadband beta -barium borate typeI phase-matching parametric amplifier is demonstrated. One can vary the number and magnitude of these components by changing amplification bandwidth (wavelength) and phase-matching conditions. The phenomenon is treated theoretically by use of a formalism developed previously for the case of cascaded self-diffraction.

Femtosecond Yb:KGW MOPA driven broadband NOPA as a frontend for TW few-cycle pulse systems

White light continuum seeded noncollinear optical parametric amplifier driven by Yb:KGW master oscillator power amplifier (MOPA) system is reported. The demonstrated design provides amplification of broadband pulses at 800 nm up to 20 µJ energy at 1 kHz repetition rate and can be used as simple and reliable frontend source for systems producing high intensity few-cycle pulses. The amplified spectral bandwidth allows for <7 fs pulse durations and preliminary compression of partial spectrum yields sub-10 fs pulse.

Generation of compressed 600-720-nm tunable femtosecond pulses by transient frequency mixing in a beta-barium borate crystal.

We demonstrate the feasibility of the compression of tunable pulses by means of sum-frequency generation under special group-velocity mismatch conditions. beta-Barium borate crystal has been shown to support the upconversion process, resulting in 160-fs pulses tunable within 600-720 nm when mixing 1.3-ps 1055-nm pulses from a Nd:glass laser with 0.95-ps pulses tunable within 1400-2200 nm from a traveling-wave parametric generator. A similar compression of ~150-fs Ti:sapphire pulses predicted for the sum-frequency tuning range of 520-590 nm.

Fivefold femtosecond pulse compression by sum frequency generation

Pulse compression by sum frequency generation is demonstrated in femtosecond time domain with a type II phase matching BBO crystal. By frequency mixing in BBO crystal infrared signal and idler pulses of 160 fs duration generated by an optical parametric amplifier, sum frequency pulses as short as 34 fs were obtained. Experiments and computer simulations demonstrate the potential of this technique to produce ultrashort pulses with high conversion efficiency.

High power, subpicosecond, 750-1770 nm tunable pulses from travelling wave parametric generator

Abstract Transform limited subpicosecond pulses have been obtained by parametric conversion of the second harmonic of a short pulse generated by a Nd:glass laser system. The arrangement consists of a KDP followed by a BBO respectively with type II and type I phase-matching, pumped in a travelling wave configuration without any spectral selecting element between them. It provides tunability from 750 to 1770 nm with pulses as short as 0.6 ps. Pulse energies above 50 μJ, with a total conversion efficiency of 13%, have been achieved.

Generation of femtosecond radiation at 211 nm by femtosecond pulse upconversion in the field of a picosecond pulse

We show that, in the case of sum-frequency mixing, one can alleviate group-velocity mismatch between IR and UV pulses by choosing different pulse widths, thus extending the interaction length of ultrashort pulses within nonlinear crystals. By fifth-harmonic generation with a Nd:glass laser, we demonstrate efficient frequency upconversion of 195-fs 264-nm pulses under the envelope of 0.9-ps 1055-nm pulses in beta-barium borate crystal, yielding <270-fs pulses with energy of up to 110muJ at 211 nm.