Mitsuru Naganuma

Studies on necessary condition of companion robot in the RAA application

This paper describes desirable properties that the companion robots should have for the application to robot assisted activity / robot assisted therapy (RAA/RAT) from the standpoint of robotics. Although animal assisted activity / robot assisted therapy (AAA/AAT) give us much better effectiveness in the hospital and old-peoples nursing home for the present time, these institutes have been looking forward to RAA/RAT because of difficulties in AAA/AAT in handling of living animals and prevention of epidemics. From the fieldwork in pediatrics ward and the nursing home using the robots on-the-market that can be partly brought up, we extracted what kind of function is effective in communication between patient-robot, patient-nurse, and patient-patient. This paper also mentions how to actualize such function by software modeling and programming.

Differential-phase-to-intensity conversion based on injection locking of a semiconductor laser

A novel method of optical phase-shift detection using differential-phase-to-intensity conversion (DPIC) based on injection locking of a semiconductor laser is proposed. We predict DPIC numerically and verify it experimentally. We then demonstrate detection of OC-48 (2.48832-Gbit/s) phase-modulated signals by use of DPIC.

A 60-GHz optical frequency shifter using coupled inverted slot lines

A millimeter-wave optical frequency shifter (OFS) using coupled inverted slot lines (ISLs) is integrated on an X-cut LiNbO/sub 3/ substrate, Theoretical analysis shows that the use of the coupled ISLs makes it possible to decrease the distance between the arms of a Mach-Zehnder interferometer for optical frequency shifting. The ISL coupling characteristics measured at 60 GHz coincide well with the calculated ones. A 60-GHz frequency shifting of a 1.3-/spl mu/m optical carrier is experimentally demonstrated using two- and four-branch OFSs. The theoretical analysis and experimental results of the two-branch OFS show that the ratio of the frequency-shifted signal intensity to the optical image intensity is in proportion to the difference between the applied dc-bias voltage and the half-wave voltage. The four-branch OFS consists of two two-branch OFSs excited 180/spl deg/ out of phase, and can suppress the optical image and original carrier simultaneously. The measurements of the four-branch OFS reveal the optical image suppression of over 12 dB and the original carrier suppression of 5 dB below the desired 60-GHz frequency-shifted signal.

Comparison of the Reaction Time Measurement System for Evaluating Robot Assisted Activities

RAA (Robot Assisted Activities) allow people to feel joy and pleasure and recover through contact with a robot. Considerable research has reported that RAA is useful for elderly persons, children hospitalized in pediatric wards and so on. However no specific evaluation method concerning RAA has yet been established. In this paper, we propose a reaction time measurement system for evaluating RAA. The level of caution or concentration of a subject can be estimated in terms of the reaction time based on visual or acoustic stimuli. We try to evaluate RAA using the variance in the reaction time before and after RAA respectively. We have developed a reaction time measurement system with hardware, following which we compared several reaction time measurement systems concerning performance and operability. We reported the results of comparisons featuring such measurement systems and the basic results of the RAA evaluation experiment using reaction time measurement. The results suggested that selection of the optimal enforcement form in RAA has been enabled through application of this reaction time measurement system.

Observation of emission decay from GaAs based 2D hole/post array structures

We have measured emission decays from 2D GaAs/AlGaAs multi-layered post/hole array structures using a decay measurement system by femtosecond-laser excitation. We have observed the fast emission decays of the 2D structures in the diagonal and lateral direction. Spectra observed in the lateral direction are shown to be stimulated emission based on the 2D photonic band gap structure.

Energy-conversion characteristics by multi-core-type photonic crystal fibers and its application

Unique measurements setup has been designed to examine the fiber-length-dependent energy conversion in multi-core-type photonic crystal fibers (PCFs) at the illumination of femto-second Ti-Sapphire laser pulses. Gradual spectral change of some peaks generating through 5 m-long PCF has been observed by using this system. Those peaks and their shifts have been identified as solitons and soliton self-frequency shift. On the other hand, the origin of peaks in shorter-wavelength regime is neither dispersive waves which are emitted and trapped by solitons nor idler waves generated by four-wave mixing or sum-frequency shift. Wavelength dispersion profiles of 5m-long PCF have been determined by measuring chromatic dispersion using a spectroscopic streak camera and the supercontinuum light, which is generated from a 20-mm-long PCF under illumination of a femto-second Ti-sapphire laser pulse.

Site-dependent nonlinear optical properties in index-guiding photonic crystal fiber

Site dependent nonlinear optical properties are characterized by pumping 140 fs pulses at independently addressable small quasi-cores formed by imperfection in index-guiding photonic crystal fiber (PCF). The positional assignment of pumping site onto the PCF is achieved based on the reflection method to observe in situ the waveguiding structure of PCF input face relative to the fixed focal point of the collimated laser beam. A series of input peak power dependent spectra at several small quasi-cores demonstrate visible light formation down to the violet, which are discussed in comparison with those for the center core leading to supercontinuum generation. Visible light formation at quasi-cores is principally due to an increase of the degree of anomalous dispersion by decreasing the core size. The observations presented in this work classify the nature of nonlinear optical processes through the slightly distorted PCF, leading to nonlinear optical manipulation by individual cores within the single PCF.

Nanometric mechaphotonics for innovative information and communications systems

Silicon-based electronics has matured and holds a dominant position in critical technologies for computing systems. Advances in micro-miniaturization techniques enable us to fabricate nanometric devices with novel functions based on mesoscopic physics, and we expect that such devices will innovate on existing systems. Optics has also made tremendous progress since the first laser to generate quasi-coherent light was developed. Lasers are now widely used in basic science and in practical applications such as information processing and communications systems. Many studies have demonstrated novel functions in logics based on not only non-linear effects of media but also quantum-optic effects in nanometer-scaled structures. However, how to overcome the diffraction limit remains an unsolved fundamental problem how to break down the diffraction limit. Here, we report some ideas for nanophotonics and present a future picture of computing systems.

Fabrication of 3D a-Si/SiO/sub 2/-photonic crystals on 2D sub-micron-patterned InP substrates

We have fabricated three-dimensional (3D) periodic structures consisting of stacked a-Si/SiO/sub 2/ layers directly on two-dimensional (2D) sub-micron-patterned [100]-InP substrates by using autocloning technology. The initial 2D pattern has been reflected in the 3D periodic structures whose height has been amplified. We have measured the transmission and reflection spectra of the 3D periodic structures, and have observed the photonic band gaps in the wavelength region of around 1400 to 2200 nm. We have also observed strong polarization dependency for the samples with the triangular lattice and weak dependency for those of the square case.