Pore-size dependent THz absorption of nano-confined water.

We performed a THz absorption spectroscopy study on liquid water confined in mesoporous silica materials, MCM-41-S-18 and MCM-41-S-21, of two different pore sizes at room temperatures. We found that stronger confinement with a smaller pore size causes reduced THz absorption, indicating reduced water mobility due to confinement. Combined with recent theoretical studies showing that the microscopic structure of water inside the nanopores can be separated into a core water region and an interfacial water region, our spectroscopy analysis further reveals a bulk-water-like THz absorption behavior in the core water region and a solid-like THz absorption behavior in the interfacial water region.

Evaluation of the hydration state of saccharides using terahertz time-domain attenuated total reflection spectroscopy.

Despite intensive studies regarding the hydration state, experimental investigations have not fully explained the global hydration state. Terahertz (THz) spectroscopy is an emerging technology that has the potential to evaluate global hydration. This is because THz waves are very sensitive to picosecond water dynamics and, as such, effectively measures the state of water that is weakly bound to solute molecules by observing slowed down water dynamics.

Highly accurate Michelson type wavelength meter that uses a rubidium stabilized 1560 nm diode laser as a wavelength reference.

We investigated the accuracy limitation of a wavelength meter installed in a vacuum chamber to enable us to develop a highly accurate meter based on a Michelson interferometer in 1550 nm optical communication bands. We found that an error of parts per million order could not be avoided using famous wavelength compensation equations. Chromatic dispersion of the refractive index in air can almost be disregarded when a 1560 nm wavelength produced by a rubidium (Rb) stabilized distributed feedback (DFB) diode laser is used as a reference wavelength.