Summary form only given. Measurements of the nonlinear absorption spectra and the dispersion of the nonlinear refraction are of interest in modeling nonlinear optical materials and determination of structure/properties relations. In the past, most of these experiments were performed at a single wavelength. Tuning over a broad spectral region can provide with a comprehensive information but, often times, one has to perform calibration of the experiment at each wavelength. An alternative is to use a white-light continuum produced by focusing short pulsed lasers into suitable media (e.g. sapphire) and using a pump-probe geometry where the probe is the continuum and the pump is an intense pulse that induces the nonlinearity. We have developed a femtosecond continuum spectrometer to measure nondegenerate spectra from 300 nm in the UV to 1.7 /spl mu/m in the IR. The pump beam is the output of a regeneratively amplified fiber ring oscillator at 775 nm or the output of a subsequent optical parametric generator/amplifier producing wavelengths from 500 nm to 1650 nm. The continuum is produced by focusing /spl sim/2 /spl mu/J of different frequencies from these two sources. Dual diode arrays for the IR and visible are used to measure the spectral changes in the transmittance against a reference beam. The spectra can be obtained as a function of time delay between pump and probe pulses. This method is applied for measuring nonlinear absorption spectra of organic materials.
Femtosecond white-light continuum for characterization of organic molecules
1999-01-01
283893 byte
Aufsatz (Konferenz)
Elektronische Ressource
Englisch
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