A measurement system for ultrafast time-resolved fluorescence spectroscopy was constructed based on electronic Kerr effect. Suitable Kerr medium was searched among glasses and isotropic single crystals by use of the Z-scan method that can evaluate the non-linear optical susceptibilities of the two-photon absorption coefficient and the photo-induced refractive index change. With optimization of design of the optical system, we achieved the time resolution of 180 femto-second, 5% gating transmittance and the one-order-faster data acquisition than conventional method.
Time-resolved spectra were measured within 20-picosecond time range for the photoactive yellow protein ( PYP ) originated from purple photosynthetic bacteria. The Kerr-gating system enabled for the first time to obtain the 2 dimensional, time - wavelength mapping of time-resolved fluorescence spectra in the femto-pico-second time region. Vibrating behavior of the fluorescence intensity peak was clearly recognized, which is curious and has never seen in dye solution systems at room temperature. It suggests that, in PYP, chromophore is energetically isolated from the main structure of amino-acid chain and that photo-excited energy is dissipates through specific channels.