< 4 ps Time-Resolved Fluorescence Spectroscopy
The experimental set-up developed for Kerr-gated resonance Raman spectroscopy can also be employed to record fluorescence spectra with < 4 ps time resolution.
The Kerr-gate is simply a fast (< 4 ps) optical gate; by controlling the point at which the gate opens slices in time through the fluorescence of a sample can be recorded.
The useful transmission range of the CS2 Kerr gate is 390-700 nm with the lower limit being set by the electronic absorption of CS2 and the upper limit set by background due to stimulated anti-Stokes emission in the medium induced by the 800 nm gating pulse. The UV coverage can be extended down to 300 nm using benzene in place of CS2.
Note: This technique cannot be employed to study naturally long lived luminescence states as the flux in 4 ps is too weak to be detected. For this an intensified charge-coupled device (ICCD) would be employed. This is an electrical rather than optical gate and hence has a longer open time.
Schematic of the Ultra Kerr-gated fluorescence setup. The red beam is the 800 nm output from the titanium-sapphire laser which is used to drive the tunable OPA and the Kerr-gate. The blue beam is the pump beam and the dashed grean line represents the fluorescence from the sample.
