Hirokazu Hori

Pseudomomentum transfer from evanescent waves to atoms measured by saturated absorption spectroscopy

Abstract We perform saturated absorption spectroscopy using counterpropagating evanescent waves at different incident angles. The experimental results show that a crossover resonance splits into two resonant peaks, and the separation increases with an increase in the difference between the incident angles of the pump and the probe evanescent waves. This indicates that the pseudomomentum of the evanescent wave, which is the wave vector along the surface multiplied by ℏ and is larger than the momentum in vacuum, is actually transferred to the atoms as a real recoil momentum.

Density of Ar Metastable Atoms on the Discharge Tube Wall Measured by Evanescent Laser Spectroscopy.

In order to measure the density of excited atoms in the metastable state on a discharge tube wall, evanescent wave spectroscopy is applied to a pure Ar discharge. In the experiments, the evanescent laser wave interacts with the Ar metastable atoms. The detection of the evanescent-laser-induced fluorescence and the laser-induced evanescent-mode fluorescence indicates the existence of metastable atoms in the vicinity of the wall within one wavelength of the laser. The absolute value of density is obtained in comparison with the signal for Rb atoms in the same system. The reflectance of metastable atoms at the wall is also estimated.

Mode‐transition characteristics and tunability of an AlGaAs laser

The wavelength characteristics of a transverse‐junction‐stripe AlGaAs laser were precisely measured for a wide range of diode temperatures and injection currents. A very simple rule was found in the mode transition characteristics. Typical features of mode competition, such as mode‐competition noise, mode hopping with and without hysteresis phenomenon, and a tristable state of the lasing wavelength, were successively observed for a single diode sample. The characteristics were analyzed theoretically by using a two‐mode intensity equation of laser oscillation under the assumption of a homogeneously broadened gain spectrum. The results were in good agreement with the experiment.

State-selective optical near-field resonant ionization spectroscopy of atoms near a dielectric surface

Spin‐sensitive optical near‐field microscopy and spectroscopy are proposed based on the study on the conserved quantities in optical near‐field interactions of atoms with dielectric surfaces. A two‐step photoionization spectra of Cs atoms resolving hyperfine structures are demonstrated near a planar dielectric surface by using evanescent waves. These techniques of state/spin‐selective excitation and highly sensitive detection, combined with the techniques of optical pumping, will open up possibilities of space‐ and polarization‐sensitive detection of optical near‐fields using atomic probes. This novel method provides us with a useful technique for the observation of polarization nature of the optical near‐field and controlling the spin states of mesoscopic electronic systems.

Observation of Coulomb Blockade and Interference Using a Carbon Nanotube Tip

Using a carbon nanotube (CNT) bundle tip as a field emitter, we have observed both Coulomb blockade and interference fringes in consecutive measurements. When Coulomb blockade is observed, decoherence of the electron wave occurs. This was observed using a double-tunnel junction consisting of a CNT tip and a CNT sample. When the CNT sample was projected onto a screen by an electron wave from the CNT tip, interference fringes were observed. This shows that the electron is first observed at the central electrode as a Coulomb blockade, next it is observed at the CNT sample as current when the electron leaves from the central electrode (the CNT tip) and finally observed as fringes passing through the CNT sample. These results show that the systems wave function cannot be written as a direct product of independent substates.

Photoluminescence of GaAs Tip Apex Excited by Evanescent Wave

To characterize the optical properties of a semiconductor tip apex or semiconductor nanoparticles attached to a tip apex, an experimental setup to detect the photoluminescence (PL) spectra of the specimens excited by the evanescent wave was constructed. The tip-prism surface distance dependency of the PL spectra was observed by means of a prism covered with conducting thin films which were used to define the origin of the separation by detecting the tunneling current. It was demonstrated that the PL intensity exponentially depends upon the separation.