We fabricated the first Fe-coated fiber probe for magneto-optical applications. In order to improve the optical confinement capability, we used a double-layer structure, with a thin coating of Au. The double-layer structure consisted of 50-nm-thick Fe and 50-nm-thick Au. A probe-to-probe experiment confirmed that the fabricated fiber probe had an effective optical confinement capability for optical near-field measurement.

In order to realize high-yield speckle modulation, we developed a novel spatial light modulator using zinc oxide single crystal doped with nitrogen ions. The distribution of dopants was optimized to induce characteristic optical functions by applying an annealing method developed by us. The device is driven by a current in the in-plane direction, which induces magnetic fields. These fields strongly interact with the doped material, and the spatial distribution of the refractive index is correspondingly modulated via external control. Using this device, we experimentally demonstrated speckle modulation, and we discuss the quantitative superiority of our approach.

The frequency of an AlGaAs DH laser has been stabilized with respect to a Fabry-Perot interferometer by controlling the injection current. The frequency stability of 2.11012 was obtained at τ90 ms, which was better than the free-funning stability by three orders of magnitude.

In-situ position-controlled lateral deposition of nanometer-size Zn and Al dots on a sapphire substrate was accomplished by dissociating diethylzinc and trimethylaluminum using an optical near field on a sharpened optical fiber probe tip. The minimum diameters of the Zn and Al dots deposited were 37 and 25 nm, respectively, comparable with the apex diameter of the fiber probe. By changing the reactant molecules during deposition, nanometric Zn and Al dots were successively deposited on the same sapphire substrate with high precision. The distance between these dots was as short as 100 nm.

We observed the optically forbidden energy transfer between cubic CuCl quantum dots coupled via an optical near-field interaction using time-resolved near-field photoluminescence (PL) spectroscopy. The energy transfer time and exciton lifetime were estimated from the rise and decay times of the PL pump-probe signal, respectively. We found that the exciton lifetime increased as the energy transfer time fell. This result strongly supports the notion that near-field interaction between QD makes the anti-parallel dipole coupling. Namely, a quantum-dots pair coupled by an optical near field has a long exciton lifetime which indicates the anti-parallel coupling of QDs forming a weakly radiative quadrupole state.

Particles several tens of nanometers in size were aligned in the desired positions in a controlled manner by using capillary force interaction and suspension flow. Latex beads 40-nm in diameter were aligned linearly around a 10-µm-hole template fabricated by lithography. Further control of their position and separation was realized using colloidal gold nanoparticles by controlling the particle-substrate and particle-particle interactions using an optical near field generated on the edge of a Si wedge, in which the separation of the colloidal gold nanoparticles was controlled by the direction of polarization.

We demonstrate a novel fiber device exhibiting magnetic circular dichroism (MCD) and Faraday rotation in sharpened optical fibers coated with Fe. The degree of MCD was 0.68 in a magnetic field of 0.35 T and the Faraday rotation angle was as great as 110 degrees. Such great magneto-optical effect is due to optical near-field interactions in the sub-wavelength region, i.e., in the tip of the near-field fiber probe. These effects can be attributed to the large magnitude of the magneto optical coefficient of Fe.

We investigated the initial stage of Zn dot growth using near-field optical chemical vapor deposition. The dependence of the rate of Zn dot deposition on dot size revealed that the deposition rate was maximal when the dot grew to a size equivalent to the probe apex diameter. Such observed size-dependent resonance was in good agreement with theoretical results for dipole-dipole coupling with a Forster field between the deposited Zn dot and the probe apex.

We introduce stepwise resonant excitation by two-color optical near fields in order to detect Rb atoms with a slit-type detector. Blue fluorescence of the second D2 line is monitored for background-free detection. Feasibility of the method is shown from an experiment with a Rb vapor cell, where a sub-Doppler spectrum with the FWHM of 80 MHz is obtained. The detection efficiency is estimated at about 3% for cold Rb atoms.

In nanophotonic device operations, characteristic features on a nanometer scale, such as locally excited states, dependence on the excitation number, and spatial symmetry of a system, play an important role. Using these features, selective excitation energy transfer via an optical near field is shown for a quantum-dot system with discrete energy levels. This selectivity strongly depends on a dipole-inactive state of an exciton, which cannot be excited by the far-field light. Operation principles of logic gates, photon storage, and quantum information processing device, which are based on the selectivity, are proposed, and the temporal dynamics are investigated analytically and numerically by using quantum theory. Nanophotonic devices, which are constructed from quantum mechanical and classical dissipative systems, are expected to become one of a key technologies in future device architecture.

We approach nanophotonic computing on the basis of optical near-field interactions between quantum dots. A table lookup, or matrix-vector multiplication, architecture is proposed. As fundamental functionality, a data summation mechanism and digital-to-analog conversion are experimentally demonstrated using CuCl quantum dots. Owing to the diffraction-limit-free nature of nanophotonics, these architectures can achieve ultrahigh density integration compared to conventional bulky optical systems, as well as low power dissipation.