33 research outputs found
Broadband coherent Raman scattering spectroscopy at 50,000,000 spectra/s
Raman scattering spectroscopy is widely used as an analytical technique in
various fields, but its measurement process tends to be slow due to the low
scattering cross-section. In the last decade, various broadband coherent Raman
scattering spectroscopy techniques have been developed to address this
limitation, achieving a measurement rate of about 100 kSpectra/s. Here, we
present a significantly increased measurement rate of 50 MSpectra/s, which is
500 times higher than the previous state-of-the-art, by developing time-stretch
coherent Raman scattering spectroscopy. Our newly-developed system, based on a
mode-locked Yb fiber laser, enables highly-efficient broadband excitation of
molecular vibrations via impulsive stimulated Raman scattering with an
ultrashort femtosecond pulse and sensitive time-stretch detection with a
picosecond probe pulse at a high repetition rate of the laser. As a
proof-of-concept demonstration, we measure broadband coherent Stokes Raman
scattering spectra of organic compounds covering the molecular fingerprint
region from 200 to 1,200 cm-1. This high-speed broadband vibrational
spectroscopy technique holds promise for unprecedented measurements of
sub-microsecond dynamics of irreversible phenomena and extremely
high-throughput measurements
Coherent Raman spectro-imaging with laser frequency combs
Optical spectroscopy and imaging of microscopic samples have opened up a wide
range of applications throughout the physical, chemical, and biological
sciences. High chemical specificity may be achieved by directly interrogating
the fundamental or low-lying vibrational energy levels of the compound
molecules. Amongst the available prevailing label-free techniques, coherent
Raman scattering has the distinguishing features of high spatial resolution
down to 200 nm and three-dimensional sectioning. However, combining fast
imaging speed and identification of multiple - and possibly unexpected-
compounds remains challenging: existing high spectral resolution schemes
require long measurement times to achieve broad spectral spans. Here we
overcome this difficulty and introduce a novel concept of coherent anti-Stokes
Raman scattering (CARS) spectro-imaging with two laser frequency combs. We
illustrate the power of our technique with high resolution (4 cm-1) Raman
spectra spanning more than 1200 cm-1 recorded within less than 15 microseconds.
Furthermore, hyperspectral images combining high spectral (10 cm-1) and spatial
(2 micrometers) resolutions are acquired at a rate of 50 pixels per second.
Real-time multiplex accessing of hyperspectral images may dramatically expand
the range of applications of nonlinear microscopy.Comment: 8 pages, 3 figure