S. Furue

Fabrication and Characterization of Cu(In,Ga)(S,Se)2-Based Solar Cells

We formed Cu(In,Ga)(S,Se)2 films using a three-stage process. The grain size of the films was reduced by increasing their S concentration. Judging from the phase diagrams of Cu–S and Cu–Se, a decrease in grain size with the increase in S concentration may be due to the higher the melting point of Cu2S compared to that of Cu2Se. The short circuit current density of the fabricated solar cells decreased significantly with an increase in S concentration. Secondary ion mass spectrometry showed an unsuitable compositional distribution of S and Se despite the constant S/Se flux ratio during growth. A maximum open circuit voltage of 0.83 V was obtained at a S/(S+Se) ratio of 0.80 in the fabricated solar cells in order to increase bandgap.

Fast Spin Dynamics of Optically Induced Magnetization in Aqueous Solutions of Magnetic Ions

Fast spin dynamics of optically induced magnetization in aqueous solutions of transition-metal ions is studied by the polarization spectroscopy. Concentration dependence suggests the decay of the magnetization is caused by the spin-spin interaction.

Optically induced magnetization and ultrafast spin dynamics of magnetic ions in ionic crystals

Optically induced magnetizations in Tm2+:CaF2 and Cr3+:A12O3 are observed by using the polarization spectroscopy. Quantum-beat free-induction decay and ultrafast spin-lattice relaxation near room temperature in the ground states of the magnetic ions are investigated..

Quantum-beat free-induction decay of copper ions in an aqueous solution: Fourier-transform ESR spectroscopy by optical means

The fast-spin dynamics of transition-metal ions in an aqueous solution at room temperature has been directly observed in the subnanosecond region by polarization spectroscopy using the pump-probe technique. The time evolution of the optically induced magnetization is monitored through the change in the polarization of the probe pulse. Quantum-beat free-induction decay signals in the ground state of copper ions in an aqueous solution of copper sulfate are observed in transverse magnetic fields. The Fourier transform of the observed signals gives the ESR spectra. From the magnetic-field dependence of the beat frequency, the g-value of copper ions is g=2.20±0.05. The observed line shape of the ESR spectra suggests that the hydrated copper complex rotates in the picosecond region. This all-optical method can be a powerful tool for the study of fast-spin dynamics in solutions.

Subnanosecond relaxation of optically‐induced magnetization in aqueous solutions of transition‐metal ions

Optically‐induced magnetization in aqueous solutions of transition‐metal ions is studied by the polarization spectroscopy. From the concentration and magnetic‐field dependences of the magnetization signal in the picosecond and nanosecond regions, it is found the observed decay of the magnetization is caused by the spin cross relaxation. The quantum‐beat free‐induction‐decay signals are observed under a transverse magnetic field. Fourier transform of the observed signals gives the ESR spectra.

Group velocity of optical pulses in resonantly absorbing media

The propagation of femtosecond optical pulses in dye solutions is studied. The observed group delay of the transmitted pulses are compared with the new definition of the group velocity.

Optically-induced magnetization and spin cross relaxation in aqueous solutions of transition-metal ions

Optically-induced magnetization in aqueous solutions of transition-metal ions is studied by the polarization spectroscopy. It is found the observed decay of the magnetization in picosecond and nanosecond regions is caused by the spin cross relaxation.