Surface-Enhanced Impulsive Coherent Vibrational Spectroscopy.
Surface-enhanced Raman spectroscopy (SERS) has attracted a lot of attention in molecular sensing because of the remarkable ability of plasmonic metal nanostructures to enhance the weak Raman scattering process. On the other hand, coherent vibrational spectroscopy triggered by impulsive excitation using ultrafast laser pulses provides complete information about the temporal evolution of molecular vibrations, allowing dynamical processes in molecular systems to be followed in "real time". Here, we combine these two concepts and demonstrate surface-enhanced impulsive vibrational spectroscopy. The vibrational modes of the ground and excited states of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV), spin-coated on a substrate covered with monodisperse silver nanoparticles, are impulsively excited with a sub-10 fs pump pulse and characterized with a delayed broad-band probe pulse. The maximum enhancement in the spectrally and temporally resolved vibrational signatures averaged over the whole sample is about 4.6, while the real-time information about the instantaneous vibrational amplitude together with the initial vibrational phase is preserved. The phase is essential to determine the vibrational contributions from the ground and excited states.
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China.
Juan
J
Du
Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland.
Juha
J
Harra
Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland.
Matti
M
Virkki
Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland.
Jyrki M
JM
Mäkelä
State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai, 201800, China.
Yuxin
Y
Leng
Department of Physics, Tampere University of Technology, P.O. Box 692, 33101, Tampere, Finland.
Martti
M
Kauranen
Ultrafast Laser Research Center, University of Electro-Communications, 1-5-1, Chofugaoka, Chofu, Tokyo, 182-8585, Japan.|JST, CREST, K's Gobancho, 7 Gobancho, Chiyoda-ku, Tokyo, 102-0076, Japan.|Advanced Ultrafast Laser Center, National Chiao-Tung University, Hsinchu, 30010, Taiwan.
Takayoshi
T
Kobayashi