ANYL 338 |
| A novel multiplex CARS microscopy technique with a single ultrafast laser pulse is demonstrated. All the pump, Stokes, probe pulses are selected from a Ti:Sapphire cavity dumping oscillator laser pulse (bandwidth ~ 120 nm) with a pulse shaper using a liquid crystal spatial light modulator. Since the measured CARS signal is a coherent sum of the resonant and non-resonant signals, the spectral interference makes the vibrational peak assignment difficult. The resonant and non-resonant CARS signals, however, have different symmetry in the time domain due to the causality principle of the vibrationally resonant excitation. A new Fourier Transform Spectral Interferometry (FTSI) is developed to discriminate the resonant signal against the non-resonant one utilizing the difference of the symmetry in the time-domain. This method extracts the pure imaginary parts of vibrational resonances, which are equivalent to the spontaneous Raman scattering peak shape, in a single experimental measurement. It also amplifies the resonant CARS signal significantly by the homodyne amplification with the non-resonant signal as a local oscillator. Amplitude control of the laser spectrum increases the available CARS spectral window with a given total power and bandwidth of the laser. Current sensitivity, available CARS window limit and application to hyperspectral vibrational microscopy are discussed. |
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Biological Applications of Nonlinear Optics
8:30 AM-12:10 PM, Tuesday, August 21, 2007 BCEC -- 104A, Oral
Division of Analytical Chemistry |