Time-gated pre-resonant femtosecond stimulated Raman spectroscopy of diethylthiatricarbocyanine iodide.
We present time-gated femtosecond stimulated Raman spectroscopy (fSRS) under the pre-resonance Raman conditions of diethylthiatricarbocyanine (DTTC) iodide. A 'pseudo emission-free' condition is achieved by delivering the probe beam ahead of the pump beam. Regeneratively amplified pulse trains are employed to create an angle-geometry (non-collimated) mixing between the pump and probe beams, leading to highly sensitive measurement of the stimulated Raman gain. Time-integrated spectroscopy allows for a more quantitative distinction between the contributions of stimulated Raman scattering and stimulated emission. We successfully obtain a highly sensitive (signal-to-noise ratio >100) stimulated Raman spectrum under the optimized conditions, which compares favourably to results obtained using two-dimensional correlation spectroscopy (2DCOS). Given the optical pre-resonance of ∼0.1 eV, the background signals mostly originate from the stimulated emission of excited electrons and are significantly reduced by partial overlapping of the pump and probe beams; a genuine fSRS spectral profile is obtained for a temporal delay of ∼0.2 ps between the two beams.
Department of Bio & Nano Chemistry, Kookmin University, Seoul 136-702, Republic of Korea.
Hyung Min
HM
Kim
Hyunmin
H
Kim
Ilseung
I
Yang
Seung Min
SM
Jin
Yung Doug
YD
Suh
D002232:Carbocyanines / Q000737:chemistry*; D013059:Spectrum Analysis, Raman / Q000379:methods*
D002232:Carbocyanines; C466485:diethylthiotricarbocyanine iodide