Sum-Frequency-Generation-Based Laser Sidebands for Tunable Femtosecond Raman Spectroscopy in the Ultraviolet

Applied Sciences

Liangdong Zhu¹  Weimin Liu¹  Yanli Wang¹  Chong Fang¹ 

[1] Department of Chemistry and the Center for Sustainable Materials Chemistry, Oregon State University, 153 Gilbert Hall, Corvallis, OR 97331, USA; E-Mails:

关键词: femtosecond spectroscopy;    four-wave mixing;    tunable laser sidebands;    stimulated Raman scattering;    resonance enhancement;    molecular vibrations;   

DOI  :  10.3390/app5020048

来源: mdpi

【 摘 要 】

Femtosecond stimulated Raman spectroscopy (FSRS) is an emerging molecular structural dynamics technique for functional materials characterization typically in the visible to near-IR range. To expand its applications we have developed a versatile FSRS setup in the ultraviolet region. We use the combination of a narrowband, ~400 nm Raman pump from a home-built second harmonic bandwidth compressor and a tunable broadband probe pulse from sum-frequency-generation-based cascaded four-wave mixing (SFG-CFWM) laser sidebands in a thin BBO crystal. The ground state Raman spectrum of a laser dye Quinolon 390 in methanol that strongly absorbs at ~355 nm is systematically studied as a standard sample to provide previously unavailable spectroscopic characterization in the vibrational domain. Both the Stokes and anti-Stokes Raman spectra can be collected by selecting different orders of SFG-CFWM sidebands as the probe pulse. The stimulated Raman gain with the 402 nm Raman pump is >21 times larger than that with the 550 nm Raman pump when measured at the 1317 cm⁻¹ peak for the aromatic ring deformation and ring-H rocking mode of the dye molecule, demonstrating that pre-resonance enhancement is effectively achieved in the unique UV-FSRS setup. This added tunability in the versatile and compact optical setup enables FSRS to better capture transient conformational snapshots of photosensitive molecules that absorb in the UV range.

【 授权许可】

CC BY   
© 2015 by the authors; licensee MDPI, Basel, Switzerland.