欅田 英之

The spectra of the third-order optical nonlinearity, \chi((3))(omega;omega,omega,-omega)\, around excitonic resonance in a spin-coated film and a Langmuir-Blodgett (LB) film of polythiophene derivative, poly(3-[2-((S)-2-methylbutoxy)ethyl]thiophene), were measured using the degenerate four-wave-mixing method. The obtained value of \chi((3))(omega;omega,omega,-omega)\ at the excitonic resonance was similar to 10(-7) esu, which was the largest value ever obtained in conjugated polymers. From the absorption spectra and \chi((3))\ spectra, the average effective conjugation lengths of the spin-coated film and the LB film were estimated to be approximately 20- and 36-thiophene rings, respectively. [S0163-1829(98)50144-0].

Third-order optical nonlinearity around the exciton resonance in (C6H13NH3)(2)PbI4 was measured using time-integrated and spectrally-resolved four-wave-mixing (FWM) techniques. For excitation below the exciton resonance, biexciton contribution to the FWM signals was observed. The dephasing energy of the biexcitons was estimated to be larger than 10 meV.

Third-order optical nonlinearity of regioregular head-to-tail coupled poly(3-hexylthiophene)(HT-PHT) was measured using degenerate four wave mixing (DFWM), and the dispersion spectrum of \X-(3)\ around the exciton absorption peak was obtained. In addition, the relaxation process of the excitons was measured using the transient grating method. The resultant decay time was less than 2 ps and consisted of two components.

無機有機複合型量子井戸物質において、励起子共鳴下で巨大な3次非線形性を発見した。

Third-order optical nonlinearity of regioregular head-to-tail coupled poly(3-hexylthiophene)(HT-PHT) was measured using degenerate four wave mixing (DFWM), and the dispersion spectrum of |χ(3)| around the exciton absorption peak was obtained. In addition, the relaxation process of the excitons was measured using the transient grating method. The resultant decay time was less than 2 ps and consisted of two components.

Third-order optical nonlinearity around the exciton resonance in (C6H13NH3)2PbI4 was measured using time-integrated and spectrally-resolved four-wave-mixing (FWM) techniques. For excitation below the exciton resonance, biexciton contribution to the FWM signals was observed. The dephasing energy of the biexcitons was estimated to be larger than 10 meV.

Ionizing collisional rate of metastable krypton and argon atoms in an optical lattice k(lattice) is compared with that in free space k(free). Reduction of the collisional rate is observed for krypton atoms. However, the magnitude of reduction is no more than a factor of 2 at the laser detuning of 7 GHz. The ratio k(lattice)/k(free) is found to change proportional to the square root of the excitation rate of atoms from the 1s5 metastable state to the 2p(9) state by the lattice laser. The mechanism that prevents a larger reduction is discussed.

Ultracold ionizing collisions of laser-cooled Kr isotopes in the 1s5[4p55s:3P2] metastable state are investigated. When the collision energy is reduced below the p-wave centrifugal barrier of 80 K, the ratio of the ionizing collision rate between polarized and unpolarized Kr83 atoms is found to decrease. This is a direct evidence of the quantum interference of two identical Fermi particles. The experimental results are compared with the calculation based on the simplified inelastic collision theory. © 1995 The American Physical Society.