Hideki Yasuda

Photocarrier recombination dynamics in highly excited SrTiO3 studied by transient absorption and photoluminescence spectroscopy

We studied photocarrier recombination processes in highly excited SrTiO3 crystals using pump-probe transient absorption (TA) and photoluminescence (PL) spectroscopy at room temperature. TA signals of nondoped SrTiO3 crystals clearly appear in the visible and infrared spectral region under intense interband photoexcitation, and TA spectra show Drude-like photon-energy dependence. Both TA and PL decay curves are well explained by the same simple rate equation including three-body Auger recombination and single-carrier trapping.

Anti-reflective coating for visible light using a silver nanodisc metasurface with a refractive index of less than 1.0

Suppression of visible-light reflection from material surfaces is an important technology for many applications such as flat-panel displays, camera lenses, and solar panels. In this study, we developed an anti-reflective coating design based on a silver nanodisc metasurface. The effective refractive index of a 10-nm-thick monolayer of silver nanodiscs was less than 1.0, which enabled strong suppression of reflection from the underlying substrate. The nanodisc structure was easy to fabricate using a conventional roll-to-roll wet-coating method. The anti-reflective structure was fabricated over a large area.Suppression of visible-light reflection from material surfaces is an important technology for many applications such as flat-panel displays, camera lenses, and solar panels. In this study, we developed an anti-reflective coating design based on a silver nanodisc metasurface. The effective refractive index of a 10-nm-thick monolayer of silver nanodiscs was less than 1.0, which enabled strong suppression of reflection from the underlying substrate. The nanodisc structure was easy to fabricate using a conventional roll-to-roll wet-coating method. The anti-reflective structure was fabricated over a large area.

Confined excitons with ultrafast radiative decay time less than 100 fs enabling survival at room temperature

Temperature dependence of degenerate four-wave mixing signal in high-quality CuCl thin films was investigated. We observed the signal of modes with large radiative width at high temperatures due to ultrafast radiative decay faster than dephasing.

Room temperature degenerate four-wave mixing due to ultrafast radiative decay of confined excitons

Degenerate four-wave mixing spectrum and the temperature dependence are investigated in a CuCl thin film with high crystalline quality. The signal at room temperature is firstly observed.

Ultrafast radiative decay of confined excitons due to long-range coherent coupling with radiation wave

Transient grating spectrum and the delay time dependence are investigated in a CuCl thin film. The structures for complex eigenmodes and the ultrafast radiative decay rates of excitons below 200 fs are observed.