High-order Raman sidebands generated from the near-infrared to ultraviolet region by four-wave Raman mixing of hydrogen using an ultrashort two-color pump beam

Abstract

A two-color pump beam consisting of a fundamental beam of a Ti:sapphire laser (35 fs, 802 nm) and a signal beam generated by optical parametric amplification (55 fs, 1203 nm) was utilized to generate multiple Raman sidebands by vibrational four-wave Raman mixing. The second harmonic emission (401 nm) was further employed as a seed beam for enhancing efficiency. Numerous sidebands emitting at 602, 481, 344, 301, 267, 241, 219, 200, and 185 nm were observed by irradiating the beam onto a screen coated with sodium salicylate. The spectral band width of these emission lines was capable of generating 0.9-fs optical pulses by Fourier synthesis.

High-Energy, Multicolor Femtosecond Pulses from the Deep Ultraviolet to the Near Infrared Generated in a Hydrogen-Filled Gas Cell and Hollow Fiber

“…The generation of multicolor laser emission via FWM has also been investigated in the femtosecond (fs) regime [8][9][10][11][12][13][14][15][16][17][18][19][20][21]. Resonant and non-resonant FWM has been investigated in bulk media [11,13,[15][16][17], leading to multicolor laser emission with a pulse energy of about 1 microjoule [17].…”

“…The efficiency of the multicolor generation can be improved by more than one order of magnitude using gaseous media rather than bulk media. In addition, the spectral range from the DUV to the NIR has been covered by employing Raman active gases as the nonlinear media for FWM [9,10,12,14,20,21]. When pumping with short fs pulses with high intensities, self-phase modulation (SPM) and cross-phase modulation (XPM) are simultaneously induced, which results in a broad spectral width for each multicolor emission.…”

“…When using the vibrational transition of molecular hydrogen with a large Raman shift frequency of 4155 cm −1 [26], it is possible to generate multicolor fs pulses with spectral widths supporting transform-limited pulse durations of about 10 fs. Multicolor generation via the vibrational transition has been investigated both in a hydrogen-filled hollow fiber using two-color fs pump pulses at 800 and 600 nm [12] and in a hydrogen-filled gas cell using shorter two-color NIR pump pulses emitting at 800 and 1200 nm [20]. These investigations have reported multicolor laser emission covering from the DUV to NIR.…”

Cross-Correlation Frequency-Resolved Optical Gating for Test-Pulse Characterization Using a Self-Diffraction Signal of a Reference Pulse

“…The spacing of the beat is determined by the frequency separation of pulses A and B, not by the relative phase. This would not be the case for an ultrashort optical pulse synthesized using more than two discrete spectral components [26], for instance a pulse train synthesized using multicolor laser emissions generated via FWM [5][6][7]19]. The characterization of an optical beat formed by two-color laser beams is useful for the evaluation of the bandwidth available in the diagnostics.…”

“…Several approaches have been reported to date for their generation. One of the approaches, four-wave Raman mixing in a hydrogen gas, generates octave-spanning multicolor emissions in the optical region [5][6][7]. By Fourier synthesis of the multicolor emissions, intense sub-2-fs optical pulses can be generated.…”