Design and characterization of a femtosecond fluorescence spectrometer based on optical Kerr gating

Design and characterization of a general-purpose spectrometer for recording time-resolved emission spectra of typical fluorescent species is described. The system is based on a high repetition rate amplified Ti: sapphire system, an optical Kerr shutter for gating the emission, and a polychromator plus charge-coupled device (CCD) detection system. Using 1 mm of liquid benzene as the Kerr medium, and optics designed to provide high polarization quality, emission spectra of dilute solutions of solutes with nanosecond lifetimes can be recorded with good signal-to-noise ratios. The current spectrometer uses excitation wavelengths near 390 nm and provides spectra over the wavelength range 400-650 nm with 4 nm resolution and instrument response times of 450 fs (full width at half-maximum, FWHM). Selected applications are described to demonstrate the utility of this instrument.