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To elucidate the dynamics and mechanisms of radiationless transitions from higher excited electronic states as well as the ultrafast intramolecular vibronic relaxation in porphyrin derivatives, we ...

Low-frequency vibrational modes of the native photoactive yellow protein (PYP) and its several mutant and analogue systems have been investigated in “time” (femtosecond fluorescence up-conversion) ...

We propose a simple coherent beam combining technique for applications in high-power multichannel laser amplifier systems with tiled aperture design. Using a photodiode pair coupled with piezo-actuator mirrors, we demonstrated robust beam combining bandwidth (∼1 KHz) and root mean-square deviation (∼λ/25) for two beam channels. We estimate that the performance of this technique can be further enhanced in terms of operational bandwidth and phase locking accuracy. It is not limited by single beam power or channel number restrictions, does not require optical phase retrieval algorithms, or calibrations, and can be integrated into various master oscillator power amplifier architectures.

The effect of the protein environment surrounding chromophores (protein nanospaces) on the photoinduced ultrafast twisting of chromophores in photoactive yellow protein (PYP) was investigated by comparing the femtosecond−picosecond fluorescence dynamics of wild type PYP with those of the chromophore in aqueous solution as well as in protein nanospace modified by site-directed mutagenesis. The rate of the twisted state formation of the chromophore (the primary step of the trans → cis photoisomerization) was demonstrated to be considerably enhanced in protein compared with the aqueous solution. Moreover, results of the measurements of fluorescence dynamics of the chromophore in the protein nanospace modified by site-directed mutagenesis implied that the twisted state formation by flipping the thioester linkage of the chromophore was slowed by modifying the nanospace structure to a slightly looser one. Namely, the more restricted structure of the protein nanospace in the wild-type PYP seems to be best engine...

Fluorescence dynamics has been studied for some porphyrin derivatives to elucidate the relation between the intramolecular energy relaxation and the electron-transfer (ET) reaction over a wide spectral range by using fs-fluorescence up-conversion technique. Zn-tetraphenylporphyrin (ZnTPP) in ethanol solution has shown fluorescence dynamics over the whole spectral range from 430 to 620 nm when excited to S2 state, which reflects the intramolecular energy-relaxation dynamics. In the short wavelength region from 430 to 500 nm, the fluorescence has shown a single-exponential decay with a time constant of ∼2.3 ps , whereas a single-exponential rise with the same time constant of ∼2.3 ps has been observed at 600 nm. In the intermediate spectral region, fluorescence rise and decay showed more or less complex behavior. These results have been qualitatively interpreted by considering two relaxation paths, an immediately relaxing one as a main relaxation channel and a slower one in which molecules are once trapped in higher vibrational states of S1. For Zn-diphenylporphyrin (ZnDPP)-electron acceptor supermolecule systems, we have confirmed that the rate of ET from S2 state decreases with increasing of the free-energy gap for ET. This is a first unambiguous observation of the inverted effect for the charge-separation process. Furthermore, ZnDPP attached to naphthylimide has shown multiexponential S1 fluorescence decay, which implies the influence of the intramolecular relaxation on the ET reaction.