Toshihiro Nishi

The Amplification Properties of a Highly Er3+-Doped Phosphate Fiber

The amplification properties of a highly Er3+-doped phosphate fiber were measured. Gain was observed in the wavelength region of 1.525-1.57 µm and the wavelength at maximum gain was 1.535 µm. Since the absorbed pump threshold obtained experimentally agreed with the calculated result, no cooperative upconversion process occurred in the 1.53 wt% Er2O3 fiber.

Fast and Efficient Photon-Gated Burning of Persistent Spectral Holes in Donor-Acceptor Electron Transfer Systems

Extremely fast and highly efficient burning of persistent spectral holes was observed for metal-free tetraphenylporphine with halogenated anthracene derivatives in poly(methylmethacrylate) or poly(ethylene) film. Persistent spectral holes were burnt when the system was irradiated with two 2.5 ns pulses [energy: 0.6 mJ/(cm2pulse)], or with two 1 or10 µs pulses [energy: 60 pJ/(cm2pulse)] at about 645 nm. The hole formation yield is independent of the time interval between frequency-selective and gating excitation up to as long as 2 min, suggesting the participation of a stable intermediate state in the reaction.

Photochemical hole burning in highly doped TPP/PMMA systems. Energy migration and stabilization of burnt holes for subsequent hole-burnings

Photochemical hole-burning experiments were performed on highly doped TPP/PMMA systems. Kinetics of the photophysical processes which compete with the PHB photochemistry, including the interguest energy migration, was analyzed. Reduction of the hole-filling efficiency accompanied by subsequent hole-burning was observed when ZnTPP was also incorporated in the system. Applicability of highly doped host-guest systems to the practical PHB optical memory was discussed.

Temperature Dependence of PHB Hole Profiles in Polymer Matrices

The temperature dependences of irreversible hole decay for tetraphenylporphines / polymers as guest / host systems were investigated. The irreversible hole decay values depend on the chemical structure of matrix polymers. Irreversible hole decay is caused by the motion of polymer side chains or backbones of poly(alkyl methacrylate)s and polyethylene. Excellent hole retention is observed in the PMMA matrix, and is explained by the small, symmetrical structure of methyl groups. PnDMA shows hole decay profiles similar to those of PE. This result indicates that PnDMA forms microstructures that are similar to PE microstructures because of long methylene side chains.

Persistent Spectral Hole-Burning in Semi-Crystalline Matrices Doped with Tetraphenylporphine

We report persistent spectral hole-burning (PSHB) in semi-crystalline polymer matrices doped with tetraphenylporphine (TPP). The host matrices were polyethylene (PE) and butadiene rubber (BR). The holewidth in TPP/PE was smaller than that observed in poly (methyl methacrylate) (PMMA) doped with TPP at about 5.5 K. However, the irreversible hole broadening measured with thermal cycling experiments was greater in PE. A similar tendency was also observed for the holewidth and irreversible hole broadening in semi-crystalline and amorphous BR matrices. These results show that the existence of the crystalline region plays an important role in the properties of spectral holes.