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ABSTRACT: High spectral resolution coherent anti-Stokes Raman scattering (CARS) spectroscopy and microscopy are demonstrated with femtosecond
laser systems. We perform optimal chirping in glass fibers and demonstrate a spectral resolution enhancement to better than
26cm−1, which is limited by the bandwidth of the measured resonances. Considering the convolution with the resonance bandwidth this
corresponds to a spectral resolution of approximately 2.5cm−1, which is an enhancement by a factor of 165 with respect to the use of bandwidth-limited pulses. In microscopic imaging,
a water background suppression of 81.5% is achieved.
Applied Physics B 05/2012; 105(4):801-805. · 2.19 Impact Factor
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ABSTRACT: We present detailed investigations of a femtosecond green-pumped optical parametric oscillator (OPO) based on lithium triborate.
As pump source, a frequency-doubled Yb-fiber laser-amplifier system is used. The OPO generates signal pulses tunable over
a spectral range from 780 to 940nm and idler pulses tunable from 1630 to 1190nm. More than 250mW are generated in the signal
beam and more than 300mW in the idler beam. Without dispersion compensation chirped signal pulses with a pulse duration between
100 and 250fs are measured. Using this system for coherent anti-Stokes Raman scattering spectroscopy, vibrational resonances
between 1110 and 6760cm−1 can be excited. Due to the chirped pulses, a spectral resolution of 100cm−1 is achieved, which is 2.5 times higher compared to an excitation with time-bandwidth limited pulses.
Applied Physics B 04/2012; 103(4):795-800. · 2.19 Impact Factor
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ABSTRACT: A femtosecond light source comprising two high-intensity beams at different wavelengths is applied to coherent anti-Stokes
Raman scattering microscopy. One wavelength is supplied by a Titanium : Sapphire oscillator, while the other is derived from
that via soliton-self-frequency shift in a microstructured fiber. Clear CARS images are acquired with the frequency difference
adjusted to resonances of polystyrene and lipids.
Applied Physics B 04/2012; 101(1):167-172. · 2.19 Impact Factor
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ABSTRACT: We numerically analyze broadband (up to 60 nm) conversion of transverse modes with long-period fiber gratings that are transiently introduced via the optical Kerr effect.
Lasers and Electro-Optics (CLEO), 2011 Conference on; 06/2011
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ABSTRACT: Label-free imaging modalities, such as coherent anti-Stokes Raman spectroscopy (CARS) microscopy, have demonstrated high contrast levels and video rate image acquisition times. CARS is a nonlinear process where two lasers coherently populate a vibrational state due to a two-photon resonant interaction. A probe laser coherently depopulates the excited state, generating light at the anti-Stokes frequency, which is collected and imaged. We show that the spatial resolution of CARS can be enhanced by modulating the ground state coherence. The resulting modulation of the CARS emission intensity introduces side bands at the Rabi frequency, to the CARS spectra. The additional laser when focused to diffraction limited Gaussian shaped intensity profile will generate a distribution of Rabi side bands that depend on the radial distance from the center of the focus. By accurately measuring the amplitudes of the side bands as the laser focus is scanned, a sub-diffraction resolution image can be constructed.
Lasers and Electro-Optics 2009 and the European Quantum Electronics Conference. CLEO Europe - EQEC 2009. European Conference on; 07/2009
