[6p-S45-1~22] 3.6 Ultrashort-pulse and high-intensity lasers

▲ [6p-S45-21] Efficient generation of ultrashort high-order anti-Stokes pulses in the DUV-VUV region by four-wave Raman mixing in hydrogen gas.

〇Phan Dinh Thang^1,2, Vu Duong^1,3, Totaro Imasaka¹ (1.Division of International Strategy, Center of Future Chemistry, Kyushu University, Japan, 2.Center For Laser Technology, National Center for Technological Progress, Hanoi, Vietnam, 3.Institute of Physics, Vietnam Academy of Science and Technology, Hanoi, Vietnam)

Keywords:ultrashort, vacuum-ultraviolet (VUV), four-wave Raman mixing, nonlinear optics, deep-ultraviolet (DUV)

In this study, we generated ultrashort laser pulses in the deep-ultraviolet (DUV) and the vacuum-ultraviolet (VUV) regions using four-wave Raman mixing (FWRM) in hydrogen gas. The pump pulse was the fundamental beam of a Ti:sapphire laser system (800 nm, 35 fs, 3.6 mJ, 1 kHz). The Stoke pulse emitting at the wavelength of 1200 nm used as the signal beam was generated by passing the fundamental beam through an optical parametric oscillate/amplifier (OPO/OPA). The probe pulse was the third harmonic of the fundamental beam at 267 nm. After being overlapped in time, three pulses were focused into a hydrogen-filled gas cell under the BOXCARS configuration. Via the FWRM process, the energy of the probe beam was converted into the Raman sidebands including the anti-Stoke in the DUV-VUV region. The BOXCARS configuration was useful not only to improve the conversion efficiency but also to separate the anti-Stoke Raman bands from the fundamental and beams. The highest efficiency was observed at c.a. 1.8 atm while the crossing angle between pump and probe pulses was about 2.67 mrad. At the optimal condition, the conversion efficiency from the probe beam to the first anti-Stoke beam (240 nm) was 18 %. The anti-Stoke sideband was observed up to the fifth order, i.e. at 172 nm.