We have been developing "fiber optic nerve systems" for "smart structures and smart materials," in which an optical fiber acts as sensor to measure distribution of strain and/or pressure along it. By embedding the fiber in structures and materials, such as buildings, bridges, aircraft fuel-tanks and pipe-lines, we can realize health monitoring function for these. We have created an original technology to analyse the distributed optical parameters along the fiber by use of synthesis of correlation characteristics of continuous lightwave. Adopting this technology, "fiber optic nerve systems," which have quite a high spatial resolution and measurement speed, have been established.

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.

Advances in a digital network society require both higher densities and higher transfer rates in all sorts of storage devices. In optical recording, the trend toward higher recording density and larger storage capacity requires novel surface recording technologies that would drastically improve recording density. To satisfy these severe requirements, we have already proposed a compact integrated optical head slider assembly for proximity optical recording based on the "near field principle". Using the optical head slider, we have successfully demonstrated readout signals from 200 to 150-nm-long bit patterns at frequency bands up to approximately 10 MHz. However, from the practical point of view, it is quite necessary to evaluate readout signals from patterns of smaller (sub-micron to sub-sub-micron) track width in order to prove high-density recording potential. In this paper, we have investigated tracking accuracy characteristics utilizing sub-micron sized alternate patterns of 1-mm length formed in a straight line in the circumferential direction of the medium. Arranging precisely the head's relative position to these recorded patterns, we have successfully obtained readout signals just crossing the sub-micron line-and-space pattern's boundaries. Assuming that an aperture runs along an accurate trajectory of the arc of a circle, readout signal amplitude variations when crossing the pattern edge at a right angle have precisely predicted. Also, the influences of track width on maximum readout signal intensity and tracking sensitivity are discussed in detail.

Scanning probe microscopy (SPM) has been an important tool to image and manipulate micro/nano scale structures. The measurement is based on the optical detection of a very small deflection of a flexible cantilever while traveling near the sample surface. However, the use of a cantilever with a sharp oxidized conical tip is quite costly, very difficult to scale up and unable to scan variable hardness surfaces, such as cell membranes in vivo. A concept of in-plane probe tip is developed. It has a carbon nanotube tip, built-in actuator and a tip deflection sensor, all assembled in the same plane. Most of all, an in-plane probe design would enable the stiffness of the probe to become tunable by using MEMS clutched springs. This allows a continuous measurement of samples with inhomogeneous surface hardness without changing the probe in the middle of a measurement.

We propose anovel application of optical coherence tomography (OCT) to monitor pit formation in laser irradiated optical storage materials. A multilayer optical storage recordable compact disk, is composed of multiple layers, each of different structure. Disks were irradiated with a Q-Switched Nd:YAG laser with an energy of 373 mJ. Post-irradiated disks were evaluated by OCT and those images were compared with optical microscopy. Our results indicate that OCT is a useful instrument to investigate pit formation in mulitlayer optical storage disks and might also provide information to optimize optical memory technology.

Optical near-field recording is a candidate technology for overcoming the diffraction limit of conventional optical recording. In our previous work, we proposed a novel optical head slider for near-field recording that we call a flexible optical head slider. An air-bearing pad pattern is formed on the apex of a cantilever-like polymeric waveguide so that, by using the cantilever itself as the slider suspension, a single body structure incorporates the functions of the flying slider, suspension, and waveguide. This structure can be expected to provide several important advantages by miniaturizing head assemblies; simplifying the assembly and optical trimming processes; and producing a lighter head, thus allowing a wider tracking bandwidth. In our previous report, the mechanical characteristics and readout signal characteristics of the flexible head slider were evaluated. In this paper, we studied the tracking control for the flexible optical head slider. To detect tracking errors, a T-shaped aperture was used. One straight part of the T-shaped aperture was set along the edge of the tracks, so the transmitted light from this part is sensitively affected by off-track displacement. Another straight part is used for readout of the data marks. The T-shaped aperture was formed through the metal layer deposited on the slider pad surface, at the end of the waveguide core, using FIB (focused ion beam) etching. Test ROM media with repeated pattern of 0.5 micron-sized dot marks was used to evaluate the position error signal.

New concept of micro/nano tools working in water solutuon has been proposed by the author. A real three dimensional micro fabrication process using photo curable polymer named "micro/nano stereolithography" has been also developed by the author's group. The latest version of this process achieved 100 nm in 3D resolution and freely movable micro/nano mechanism are easily fabricated within 20 min. Nano tweezers and nano needle with two degrees of freedom were successfully fabricated without any assembly process. Cell and delicate biological materials can be remotely handled with neither any micro actuators nor lead wire. It was verified that this light-driven micro tool has precise force control with 10 FtN. These light-driven micro tools contribute to cellular biology as well as medical tools. The second application of microstereolithography is the biochemical IC chips for both micro chemical analysis and synthesis. Unlike conventional "lab. on a chip" and "micro total analysis system" (micro-TAS), our biochemical IC has micro pumps and active valves in one chip. Users can construct their own micro chemical device by themselves. The advanced biochemical IC chip-set for "on chip cell-free protein synthesis" has been prototyped and verified experimentally. A luminous enzyme of fire fly so called "Luciferase" and useful bio-marker protein "GFP" were synthesized successfully. According to above results, the biomchemical IC chips will be useful to "Order-made medicine" in near future.

Flip-chip bonding of various optical components on a silicon substrate by passive optical alignment, which eliminates complicated optical axis precise alignment, has opened up many new possibilities in constructing highly functional, reliable, and low-cost optical micro-systems. Using this technique several micro-sensors have been developed. Moreover, for future optical micro-systems, a novel method of a low temperature flip-chip bonding using surface activated bonding process has been introduced.

MEMS (micro electro-mechanical systems) are often expected to take a development as microelectronics did in the last 35 years. Several devices are already established in mass markets like acceleration sensors, gyros, pressure sensors, ink jet heads and the DLP micromirror array. On the other hand many companies have stopped their business after the telecom bubble. Others are struggling. Many dreams based on MEMS-devices that were not at all mature and could not be manufactured in high numbers. When a commercial product is the goal, several questions must be answered already in concept phase. The specifications must clearly reflect the requirements of the application. Performance and price must be competitive to any other technology. The relation between fabrication process and design is strong and mutual. The process must create all features of the device and the design must consider the limitations of the process. Only if the design is tolerant against all process variations reproducible performance can be achieved. And only if the design is robust in all process steps the devices can survive. Regarding the time and cost frame it is always preferable to change the layout rather than the process. This article looks at MEMS technology and identifies what has been adopted from CMOS, what is desirable to adopt and what needs new solutions. Examples are given in the fields of design, modeling layout, process, test, and packaging.

In recent years, the researches about Micro/Nano Systems are down actively in the bio-medical research fields, DNA research fields, chemical analysis systems fields, etc. In the results, a new materials and new functions in the systems are developed. In this invited paper, Mechano-Micro/Nano Systems, especially, motion systems are introduced. First, the research activities concerning the Mechano-Micro/Nano Systems in the world(MST2003, MEMS2003 and MEMS2004) and in Japan(Researech Projects on Nanotechnology and Materials in Ministry of Education, Culture, Sports, Science and Technology) are shown. Secondary, my research activities are introduced. As my research activities, (1) a comb-drive static actuator for the motion convert mechanisms, (2) a micro-nano fabrication method by use of FAB(Fast Atom Beam) machines, (3) a micro optical mirror manipulator for inputs-outputs optical switches, (4) a miniature pantograph mechanism with large-deflective hinges and links made of plastics are discussed and their performances are explained.

In these days, various researches for biomedical application of robots have been carried out. Particularly, robotic manipulation of the biological cells has been studied by many researchers. Usually, most of the biological cell's shape is sphere. Commercial biological manipulation systems have been utilized the 2-Dimensional images through the optical microscopes only. Moreover, manipulation of the biological cells mainly depends on the subjective viewpoint of an operator. Due to these reasons, there exist lots of problems such as slippery and destruction of the cell membrane and damage of the pipette tip etc. In order to overcome the problems, we have proposed a vision-guided biological cell manipulation system. The newly proposed manipulation system makes use of vision and graphic techniques. Through the proposed procedures, an operator can inject the biological cell scientifically and objectively. Also, the proposed manipulation system can measure the contact force occurred at injection of a biological cell. It can be transmitted a measured force to the operator by the proposed haptic device. Consequently, the proposed manipulation system could safely handle the biological cells without any damage. This paper presents the introduction of our vision-guided manipulation techniques and the concept of the contact force sensing. Through a series of experiments the proposed vision-guided manipulation system shows the possibility of application for precision manipulation of the biological cell such as DNA.

Currently, diagnosis of cancer is performed by biopsy, whereby medical doctors observe a removed specimen, focusing their attention on morphological changes in the cell sequence and cell nuclei. For early cancer, the only effect is a slight increase in the size of the cell nuclei in comparison with normal cells. Based on medical knowledge, it is presumed that an extremely small amount of a specific protein may be contained in a cell nucleus. We propose spectroscopy-tomography of single cell to measure slight changes in this protein. This technology is composed of two elemental technologies, high spatial resolution spectrometry and a precise single cell rotating method. We propose variable phase-contrast spectrometry as the high spatial resolution spectrometry and proximal two-beam optical tweezers as the precise rotating method. By these methods, we can obtain a 3-dimensional distribution of the cell components to a high spatial resolution. We verified the accuracy of variable phase-contrast spectrometry by measuring the height of a diffraction grating. We confirmed that a microsphere can be rotated by proximal two-beam optical tweezers.

We have succeeded in retrieval of λ-DNA molecules (DNAs) with micromachined DNA tweezers and reported the retrieved DNAs are insulating. Two kinds of fabrication methods of narrow gap DNA tweezers are demonstrated. In order to form a pair of opposing sharp probes with nano meter size gap, an etch stop mechanism was examined for etching process by monitoring current between the probes. In a wet etching method, a free-standing Si bridge structure having a small cross-sectional portion is firstly formed and dipped into a small drop of KOH solution which was cooled using a peltiert device. Then an AC voltage is applied through the structure, which heats the portion of the bridge dominantly as well as the surrounding KOH solution. As the result, the local Si etching by the KOH solution lasts as long as the structure is bridged. Using this method, we could fabricate 50nm-gap DNA tweezers. In a dry etching, we also succeeded in narrow gap fabrication by etching a free-standing Si bridge structure in the probes tip of DNA tweezers using fluorine radical. The tweezers fabricated by dry etching have a pair of opposing probes with 120nm-gap.

This paper reports on a new micro optical reflector made of an organic elastomer, Polydimethylsiloxane (PDMS), which achieves multi-axis motion with a single actuator layer. The whole device structure incorporates Au-coated three-dimensional PDMS micro reflector integrated with electrostatic MEMS actuators on a silicon chip by a new fabrication method named "Soft-Lithographic Lift-Off and Grafting (SLLOG)" process. The SLLOG process is a low-temperature (less than 150°C) microfabrication technique that allows soft lithographically molded PDMS micro-structures to be integrated together with silicon micromachined device patterns. The developed PDMS/silicon hybrid device reflects visible light with fast response and large rotational motion through taking advantage of the mechanical compliance of PDMS structures. The demonstrated PDMS-based reflector can achieve 4.6 micron vertical displacement using AC actuation voltage of 40 V at frequency of 1.0 kHz, and ±1.43° scanning angles using AC actuation voltage of 40 V at resonant frequency of 5.0 kHz, and ±0.85° scanning angles for static operation at 60V.

In this paper, an ultra-sharp tungsten needle electrode for field emission electron beam using the electro-chemical etching method is fabricated and the current-voltage (I-V) characteristics, emission stability, angular and energy distribution of beam are evaluated. In our setup, NaOH and KOH are used as electrolyte solution in order to fabricate the needle electrode. Throughout the experiments, we observes that the taper length of needle electrode varies from 150 μm to 250 μm according to the applied voltage and the concentration. The electron beam stability is measured to be within 5% for total emission current during 4 hours operation. Meanwhile, the ignition voltage is measured to be low at ~300V. The radius of curvature for needle electrode is experimentally found to be 220Å using a linear fitting of Fowler-Nordheim plot, which is in remarkably good agreement with that of image size obtained from a scanning ion microscope.

We propose a tunable hollow optical waveguide with a variable air core toward a new class of photonic integrated circuits. We present various unique features in hollow waveguides and the combination with microelectro-mechanical system (MEMS) will gives us widely tunable waveguide devices. We presente the design and fabrication of a tunable hollow waveguide with a variable air core. We describe the full-vectorial modeling of 3D and slab hollow waveguides with a variable air core, which is also supported by experiments. We demonstrated low loss and polarization insensitive waveguiding in an air core with optimized multilayer coating. The result shows a possibility of a large change of ~3% in propagation constant with a variable air core. We will present a wide variety of device applications based on hollow waveguides, which include tunable grating demultiplexers, variable attenuators, optical switches, tunable Bragg reflectors, tunable dispersion compensators and tunable lasers. The device structure can be formed by fully planar fabrication processes based on lithography and etching. The proposed concept may open up a new class of various tunable optical devices, which give us unique features of wide tunability, compact size and temperature insensitivity.

Metal optical waveguides and the applications to nano-optical circuits are studied. The concept of "low-dimensional optical waves" is introduced for simplicity. Propagation modes of slab and cylindrical waveguides are analyzed theoretically.

This paper describes surface plasmon polariton (SPP) modes that show extraordinary propagation behaviors along metal stripes with finite width, including multiple energy condensations. Phenomenological and quantitative investigations are carried out on these behaviors. Images of SPP modes at output edges for wide stripes exhibit multiple spots that spanned the lateral side of the stripes. The spot number is monotonously decreased as the stripe length increases. Besides, the input versus output power ratio shows a stepwise change as changing the propagation distance. We present a model of SPP modes to explain these behaviors.

Surface-plasmon polaritons (SPPs) existing at metal-dielectric interfaces with exponentially damped vertical intensity profiles have attracted much interest for their capability of confining light energy into a small space beyond the diffraction limit. Theoretical considerations have been given to understandings of wave behaviors based on Maxwell's equations taking into account metals as dielectric materials with negative permittivity. However, since this approach assumes metals as homogeneous media, it is difficult to perform detailed analysis on propagation mechanisms in three-dimensional micro and nano structures. Here we propose a theoretical method based on the dynamics of electric dipoles formed by local displacement of free electrons in metals to describe SPP waves. In this method, the Poisson equation is used to describe actual movement of electrons in metals interacting with the electromagnetic field. Based on this method, we have revealed fundamental properties including electron density distribution functions in the area close to metal surfaces, SPP waves are then modeled by reconstructing microscopic features of such novel electromagnetic waves in a given material systems. After this simple verification, we make the best use of this method to explain SPP propagation at ultra-thin metal films or along narrow metal wires.

An overview of the current state of the art in scanning micromirror technology for switching, imaging, and beam steering applications is presented. The requirements that drive the design and fabrication technology are covered. Electrostatic, electromagnetic, and magnetic actuation techniques are discussed as well as the motivation toward combdrive configurations from parallel plate configurations for large diameter (mm range) scanners. Suitability of surface micromachining, bulk micromachining, and silicon on insulator (SOI) micromachining technology is presented in the context of the length scale and performance for given scanner applications.

The ability to transparently switch optical signals from one fiber to another without conversion to the electrical domain is a basic functionality that has a wide range of applications within the fiber optic industry. The so-called 3D-MEMS architecture has emerged as the preferred approach for building transparent, scalable systems with port-counts ranging from 16x16 to 1024x1024. The primary components of the 3D-MEMS architecture are fiber array, lens array, and MEMS mirror array. While a central theme in the MEMS industry is integration, we adopted a strategy of modularization. The key MEMS components, which include mirror array, ceramic substrate, and high-voltage drivers, were manufactured separately and then combined to yield a working product. Central to our modular approach was critical design parameter tolerancing to ensure manufacturability. Results from a large sampling of MEMS components and MEMS assemblies are presented to highlight manufacturability and performance.

Dynamic display and imagin applications demand high performance scanners, which has high frequency (exceeding 10KHz), large scan-angle-mirror-size product (>±10deg.mm), good optical surface quality (<λ/20 static and dynamic flatness), high sensitivity position sensors, and high-torque actuators that are compact and low power. This paper discusses the resolution and other optical performance requirements for diffraction-limited and non-diffraction-limited ligh sources in a scanning system. A set of analytical formulas is presented for calculating the torsion and other four fundamental oscillation mode vibration frequencies. The formulas include the effects of material anisotropy in orthotropic materials, such as Silicon and effective mass and inertia of the flexures. The validity range of formulas are extended by introducing a correction factor based on flexure width and flexure length ratios. The formulas are very efficient for performance trades and optimization. For scanner actuation, we present two compact scanner actuation mechanisms: out-of-plane comb actuator and novel two-coil electromagnetic actuator.

This paper presents a superelastic alloy microgripper with integrated electromagnetic actuators and piezoelectric sensors. The design parameters for electromagnetic actuators in the microgripper are selected based on the sensitivity analysis using FEM analysis. For integration of miniature force sensors in the microgripper, the sensor design based on the piezoelectric polymer PVDF film and fabrication process are also presented. Electro discharge machining technology is employed to fabricate the microgripper structure made of superelastic NiTi alloy. The experimental setup is implemented to evaluate the performance of the fabricated force sensors and electromagnetic actuators integrated into the microgripper. Finally, results of finite element computer simulations for electromagnetic actuators and piezoelectric polymer sensors are compared with experimental results.

A variable optical attenuator (VOA) is a tunable device that can control the amount of the attenuation of the laser power in the optical communication systems. We proposed a new construction of the VOA composed of lenses and fibers and micro-actuators, which are very simple and easy to assemble. By the constructed devices, the good optical characteristics such as an insertion loss, a wavelength dependency and dynamic range are confirmed experimentally.

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.

We propose a new approach to realize a bidirectional linear repeater suitable for future optical internet networks and fault location in repeater chain with OTDR. The proposed approach is the linear repeater of simple configuration whose directionality is rearranged dynamically by electrical control signal. The repeater is composed of a magneto-optical switch, a circulator, a dynamically gain stabilized unidirectional EDFA, and control circuits. The repeater directionality is rearranged as fast as 0.1ms by an electrical control pulse. It is experimentally confirmed that OTDR with the directionality switchable repeater is feasible for repeater chain. The detailed design and performance of the repeater are also discussed, including the multi-pass interference (MPI) which may arise in the proposed repeater, the effect of the MPI on SNR degradation of the repeater chain and the feed-forward EDFA gain control circuit.

We propose a metamorphic network system, based on autonomously controlled wavelength division multiplexed devices. We will address the issue of how to assure and manage wavelength accuracy and controllability over the whole network to implement practical optical path routed networks. Our solution uses smart devices with wavelength calibration tables to construct systems that can be self-controlled according to their own stored physical layer information. The devices are interactive and share renewable information and are therefore useful for realizing self-reconfigurable (metamorphic) network systems. To verify the proposed architecture, we performed practical examinations using subsystems with wavelength-managed 'disk filters' in a field trial (Chitose trial).

Chaotic fluctuation of light, which is being intrinsically different from deterministic chaos in lasers, arises from quantum-optic stochastic processes, and it therefore cannot be artificially replicated. When the fluctuation is correlative, however, it will be of more use in practical applications such as cryptographic communications. Throughout various experiments, it was found that a double-ring laser having a common semiconductor gain medium with strong saturation characteristics can produce a stable light beam consisting of negatively correlative dual-color components. Although each component decomposed by chromatic beam splitting is chaotic, their combination regenerates a stable light beam. This means that the photon-number states can be controlled by using an optical processing scheme for a correlative dual-color chaotic beam. How such a beam is generated is explained by a simple numerical simulation using a finite Markov chain model that assumes strong short-term intensity correlation between the components. A possible cryptosystem is presented based on the controllability of the photon-number state.