Study of Stimulated Raman Spectroscopy
for various molecules
†,‡
Lim ,
Sohee
Bonghwan
†Center
†,‡
Chon ,
*,§
Rhee
Hanju
and Minhaeng
*,†,‡
Cho
for Molecular Spectroscopy and Dynamics, Institute for Basic Science (IBS)
‡Department of Chemistry, Korea University
§Division of Analytical Research, Korea Basic Science Institute
*[email protected], *[email protected]
 Vibrational spectroscopy by Raman scattering process
Spontanuous Raman scattering
 Stimulated Raman Scattering (SRS) energy diagram
Stimulated Raman spectroscopy
Phase matching
condition
Loss features
(anti-Stokes side)
Extracted
Raman
spectrum
Ks = ks – kp + kp
Energy
ωs = ωs – ωp + ωp
Virtual level
 In the spontaneous Raman spectroscopy a coherent pump beam at ωp is incident on a sample,
and Stokes ωS or anti-Stokes ωAS photons are generated.
 However, the stimulated Raman scattering (SRS) is a four-wave interaction. The Stimulated Raman
Scattering (SRS) represents one of the third-order nonlinear optical processes.
Thick dashed lines represent Raman active
vibrational modes. Thin dashed lines stand for
virtual levels.
Raman pump (fs)
(Stimulating pulse)
Gain features
(Stokes side)
Raman active
vibrational
modes
Stimulated Raman interactions between a white
light probe pulse (frequency components, ωprobe)
and an intense Raman pump pulse (ωpump)
cause amplifications (stokes side) and signal
reductions (anti-Stokes side) of the white light.
Raman active
vibrational
modes
Intensity
 Layout of the stimulated Raman spectrometer (Raman loss measurement)
Pharos
Centered at
1025nm
λ/2
P1
NBF
(1030nm)
Raman Pump
Delay Stage
Anti-stokes Raman Probe
NOPA
A
P2
SP
Anti-stokes beam
1.5
Amplitude (a.u.)
A
Raman pump and Raman probe spectra
WS
(755-1030nm)
Sample
1.0
0.5
Δv (FWHM) = ~ 1360 cm-1
= ~ 109 nm
0.0
800
A
PD
P
SP
NBF
/2
WS
COPA
NOPA
Monochoromator
CCD
PD
Attenuator
Photodiode
Polarizer
Strain Plate
Narrow bandpass filter
Half wave plate (1030 nm)
Wavelength Separator
Colinear Optical Parametric Oscillator
Nonlinear Optical Parametric Oscillator
850
900
950
Raman pump (before filter)
Raman pump (after filter)
1.2
Normalized Intensity (a.u.)

Centered at 1030nm
1.0
Raman pump
0.8
Δv (FWHM) = ~ 156 cm-1
= ~ 12 nm
0.6
Raman pump
0.4
after NBP filter
0.2
Δv (FWHM) = ~ 12 cm-1
0.0
= ~ 1 nm
1000
1000
Wavelength (nm)
1010
1020
1040
1050

Two narrow band-pass filters (1030 nm) are used for generating the spectrally narrow pulse. The fundamental pump beam is centered at 1030nm,
after filter pair, the pump pulse is centered at 1024 nm with a bandwidth of 12 cm–1. Because we can control the center of pump pulse by tilting
angle of narrow band-pass filters.

A broadband Raman probe pulse (800–980 nm) providing the Anti-stokes field (the spectral window from 400 cm-1 to 1800 cm-1) with a 130 fs
NOPA (Nonlinear Optical Parametric Oscillator). When the two fields overlap spatially and temporally on the sample, we can observe loss features on
the probe beam.

(+)-α-pinene
Toluene
1030
Wavelength (nm)
 Stimulated Raman spectra
Benzene
Fundamental
(-)-Limonene
Spontaneous Raman spectrum
Polystyrene
10000
Styrene (monomer)
8000
Stimulated Raman
Spontaneous Raman
Stimulated Raman
Stimulated Raman
Spontaneous Raman
Spontaneous Raman
Intensity (arb.)
Intensity (arb.)
Stimulated Raman
Spontaneous Raman
6000
4000
2000
0
400
600
800
1000
1200
1400
-1
Raman shift (cm )
1600
1800 400
600
800
1000
1200
1400
-1
Raman shift (cm )
1600
1800
400
600
800
1000
1200
1400
-1
Raman shift (cm )
1600
1800
600
700
800
500
900
1000
 The probe spectrum for the Raman pump on and off, gives the loss spectrum (upper). The peak positions are well correlated with them of
the spontaneous Raman spectra (lower).
 Benzene and Toluene which has ring structure are used for a reference in Raman spectroscopy, because these molecules have the strong
Raman active mode around ~1000 cm-1 (the ring vibration mode).
Raman optical activity (ROA) as a vibrational chiroptical probe has been proven to be of critical use in distinguishing different
structural chiralities induced by molecular vibration by measuring a difference between vibrational Raman scatterings for left- and
right-circularly polarized (LCP and RCP) radiation. However, the conventional ROA measurement method suffers from the intrinsic
weakness of the corresponding signal (10-5 ~ 10-3 of Raman intensity), which has restricted its wide range of applications including
time-resolved and space-resolved microscopic studies.
We are currently extending this approach to ROA measurement and combining it with coherent Raman process such as
stimulated Raman scattering (SRS) to achieve an effective ROA measurement. We anticipate that this new approach will be
applicable to femtosecond ROA spectroscopy and chiral microscopy for stereo-chemical imaging of chiral drugs and biomolecules.
2500
3000
3500
4000
-1
Raman shift (cm )
Chiroptical spectroscopy offers decisive information on stereochemical structures of chiral molecules in condensed phase. In particular,
2000
Raman shift (cm )
-1
 Future work
1500

Raman spectra were collected on a confocal microRaman spectrometer equipped with a grating with a
600 grooves per mm, a CCD detector with a Pelletier
cooling, and a 100 × objective.

Raman spectra were excited by 532 nm beam with 50
mW power.
 References
[1] David W. McCamant, Philipp Kukura, and
Richard A. Mathies, “Femtosecond broadband
stimulated Raman: A new approach for highperformance vibrational spectroscopy”, Appl.
Spectrosc. 57, 1317 (2003).
[2] Seung Min Jin, Young Jong Lee, Jongwan
Yu, and Seong Keun Kim, “Development of
femtosecond stimulated Raman spectroscopy:
stimulated Raman gain via elimination of cross
phase modulation”, Bull. Korean. Chem. Soc. 25,
1829 (2004)