Article

Tunable light source for coherent anti-Stokes Raman scattering microspectroscopy based on the soliton self-frequency shift.

Department of Physics and Astronomy, University of Aarhus, Aarhus, Denmark.
Optics Letters (impact factor: 3.4). 06/2006; 31(9):1328-30. pp.1328-30
Source: PubMed

ABSTRACT We present a photonic crystal fiber (PCF)-based light source for generating tunable excitation pulses (pump and Stokes) that are applicable to coherent anti-Stokes Raman scattering (CARS) microspectroscopy. The laser employed is an unamplified Ti:sapphire femtosecond laser oscillator. The CARS pump pulse is generated by spectral compression of a laser pulse in a PCF. The Stokes pulse is generated by redshifting a laser pulse in a PCF through the soliton self-frequency shift. This setup allows for probing up to 4000 cm(-1) with a spectral resolution of approximately 25 cm(-1). We characterize the stability and robustness of CARS microspectroscopy employing this light source.

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    Article: Photonic Crystal Fiber Based Time-Resolved Coherent Anti-Stokes Raman Scattering Spectroscopy
    Arthur Dogariu, Yu Huang, Marlan O Scully
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    ABSTRACT: We demonstrate a novel technique for three-color time-resolved coherent anti-Stokes Raman scattering using a Ti:Sapphire oscillator and four-wave mixing in a photonic crystal fiber. We measure vibrational coherence decays in calcite and several molecules. Femtosecond time-resolved coherent anti-Stokes Raman scattering (fs-CARS) measurements provide chemical information by recording the molecular vibrational dynamics in the time domain. In a fs-CARS experiment, the molecules are excited to one or more Raman-active vibrational modes by two coherent laser pulses, namely pump and Stokes pulses. The created vibrational coherence due to the Raman excitation is subsequently probed by a delayed third pulse, and generates a CARS signal, which is resonantly enhanced when the difference frequency between the pump and Stokes pulses matches with the frequency of a Raman transition, providing chemical information of the sample. Complicated and costly laser systems such as two optical parametric amplifiers with a Ti:Sapphire regenerative amplifier system are usually used to generate different wavelengths. Recently however, there is an emerging interest in multi-wavelength pulses generation through the nonlinear interaction between Ti:Sapphire oscillator and a photonic crystal fiber (PCF), taking advantage of the continuum and/or soliton generation in PCF.[1-4] Fig. 1a. Experimental setup (left) and b. The pump, Stokes, and probe beam spectra as generated in the PCF. The inset shows the cross-correlation between the generated Stokes and probe, with a temporal resolution of 200fs.
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Keywords

applicable
 
CARS
 
CARS microspectroscopy
 
CARS pump pulse
 
coherent anti-Stokes Raman scattering
 
photonic crystal fiber
 
setup
 
soliton self-frequency shift
 
spectral compression
 
spectral resolution
 
Stokes
 
Stokes pulse
 

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