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Nanometer-sized polygonal pits were created on a silicon plate by the laser ablation and the alkaline etching processes. A spherical aberration of the lens as well as an off-focus laser irradiation generated a small beam spot over a long distance, which was useful for creating the nano-textures. A silicon plate with a nano-pit array exhibited a reduced reflection loss in the infrared.

Dye-doped rubber rings were spitted with a glass fiber to induce a coupling between the fiber mode and the torus mode that circulated in the ring cross-section. Consequently, a laser emission of the ring emerged from the fiber end. When the rings with different emission wavelengths were spitted with a single fiber, a competitive emission took place due to the coupling between the rings.

Time-resolved spectrometry was conducted by the use of a continuous-wave laser diode and an ordinary CCD-based spectrometer. These slow devices realized a temporal resolution of ~100 ns by achieving time-space conversion with a spinning polygon mirror. Decay processes of fluorescent materials were measured successfully by using this spectrometer.

A time-resolved spectral measurement system was developed for analysis of fluorescent materials. This system used no fast-response instruments but consisted of a continuous-wave laser diode and an ordinary CCD-based spectrometer (exposure time: 1 s). A galvano-mirror with a vibration frequency of 30 Hz realized an efficient spectral measurement with a time resolution of 12 $\mu$ s. This method is simple and useful for analyses of photoluminescence processes including illumination and biosensing.

Measurement and control of rapid optical processes usually require pulsed lasers or fast-response instruments, which are too expensive or complicated for use in industries. A motor-driven polygon mirror can deflect an optical beam so that it passes across a distance of 1 mm in 5 ns, i.e., a sweep velocity of 190 km/s. This time-space conversion realizes rapid modulation of a continuous-wave beam and observation of nano-second phenomena. This article reports some experimental results that were attained by the use of this sweep method.

Liquid crystals are useful for creating spectral filters, since they exhibit a large birefringence and an efficient electro-optic effect. Liquid crystal devices, however, usually require a polarizer that halves light intensity. This polarization dependence is unfavorable particularly in the long-wavelength infrared region in which neither efficient polarizers nor strong light sources is available due to opaqueness of ordinary optical materials. Polarizer-free devices are therefore desired for extending the application fields of liquid crystals. A solution is to split a light signal into two beams with orthogonal polarization directions and superpose them after transmission through a liquid crystal cell. This optical system, however, has to be constructed with multiple optical components, which require a complicated alignment process and induce high insertion losses for infrared light. It is therefore beneficial to integrate multiple components in a single device. A compact optical device that integrates a polarization beam splitter and two retarders can be constructed by using silicon pentaprisms. The silicon prisms act as a substrate and an electrode for a nematic liquid crystal that achieves both polarization division and retardation. A function of a tunable spectral filter (Lyot filter) is attainable in the 2–8 μm wavelength range. Another solution for creating a polarizer-free device is to eliminate an optical anisotropy of the liquid crystal. Unique optical properties of cholesteric liquid crystals realize a polarization-independent index change. Whereas visible light changes its polarization direction as it passes through a chiral structure of the cholesteric liquid crystal, infrared light keeps its polarization state since their wavelength is too long to recognize the micro chiral structure. Consequently, the cholesteric liquid crystal exhibits an isotropic index of refraction that is tunable by voltage application. This isotropic property is useful to create a polarizer-free liquid crystal device. Interference filters (Fabry-Perot filters) for the infrared measurements can be constructed by enclosing a cholesteric liquid crystal in a narrow gap of two silicon plates. A polarization-independent index change between 1.52 and 1.61 is attainable by application of ~10 V.

Polyethylene glycol (PEG) exhibits a strong scattering in the solid phase whereas it is transparent in the liquid phase. Since various molecules and ions, e.g., organic dyes and fluorescent lanthanides, are soluble in bipolar PEG, it acts as a tunable matrix for those guest materials. When a fluorescent dye (rhodamine 6G) is dispersed in PEG, the strong scattering in the solid phase induces random lasing that exhibits a narrow peak in the fluorescence spectrum. This stimulated emission peak, however, reduces to a weak, broad spectrum of a spontaneous emission through the phase transition process to the transparent liquid. Regarding the lanthanide ions (europium, erbium, etc.), which generally require a long optical path for absorbing excitation light, a stronger photoluminescence occurs in the solid phase than the transparent liquid phase, since the scattering extends the optical path of the excitation light. In addition to this scattering characteristic, PEG exhibits a bistability (hysteresis) in the phase transition process; i.e., the melting point is higher than the freezing point. Consequently, both the solid and liquid phases are stable in a specific temperature range. This bistable range extends by mixing PEGs with different molecular weights; e.g., a mixture of PEGs with molecular weights of 300 and 2000 takes both the solid and liquid phases in the range between 2 and 38 °C. This bistable scattering matrix is useful to realize controllable optical devices including tunable lasers and rewritable signboards.

Deformable ring lasers were fabricated by dispersing fluorescent dye (rhodamine 6G) in silicone rubber rings, i.e., the so-called O-rings. When excited with a pulsed green laser, an O-ring of 750 µm diameter exhibited a stimulated emission with a threshold fluence of 20 µJ/mm2. The wavelength and directionality of the emission were tunable by expansion or distortion of the ring with a needle. Because of this flexibility, the fluorescent peak of the O-ring lasers was not too sharp (a low-Q emission) and its wavelength differed slightly with individual rings. These features were advantageous for inducing a cooperative emission through an optical coupling of the rings. The optical coupling could be attained by exciting a cross-sectional circulation mode (torus mode), which the O-ring held in addition to the ordinary whispering gallery mode. When an O-ring was spitted with a glass fiber, for example, the torus mode coupled with the fiber mode, and consequently, the ring fluorescence emerged from the fiber end. Multiple O-rings, which individually exhibited a different emission wavelength, generated a single emission peak due to the optical coupling when they were arranged together on a spit fiber.Deformable ring lasers were fabricated by dispersing fluorescent dye (rhodamine 6G) in silicone rubber rings, i.e., the so-called O-rings. When excited with a pulsed green laser, an O-ring of 750 µm diameter exhibited a stimulated emission with a threshold fluence of 20 µJ/mm2. The wavelength and directionality of the emission were tunable by expansion or distortion of the ring with a needle. Because of this flexibility, the fluorescent peak of the O-ring lasers was not too sharp (a low-Q emission) and its wavelength differed slightly with individual rings. These features were advantageous for inducing a cooperative emission through an optical coupling of the rings. The optical coupling could be attained by exciting a cross-sectional circulation mode (torus mode), which the O-ring held in addition to the ordinary whispering gallery mode. When an O-ring was spitted with a glass fiber, for example, the torus mode coupled with the fiber mode, and consequently, the ring fluorescence emerged from the fiber end...

Polyethylene glycol takes both transparent and translucent phases during the phase transition process at around room temperature. This bistability seems useful to create optical devices including 3D displays and tunable random lasers. These devices, however, require a spot-heating technique that controls the phase of each microelement. Self-heating of microelements is achievable if the electric conductivity of the polyethylene glycol is enhanced by the dissolution of alkaline halide salts.

Disk resonators are difficult to create with droplets, since they self-form spheres due to the surface tension. In this study, disk (cylindrical) droplets were created by enclosing a dye (rhodamine 6G) solution in silicone rubber. Lasing actions of these droplets were examined by pulsed green laser excitation. In a large droplet (2 mm diameter), the whispering gallery mode emission was difficult to attain, since it competed with the radial or axial modes that made a round trip in the droplet. A disk droplet of 150 μm diameter exhibited a comb-like spectrum of the whispering gallery mode resonant emission.

The dependences of the incident angle and thermal durability of a tungsten silicide (WSi) wire-grid polarizer were examined. A WSi grating with a 0.5 fill factor, 260 nm depth, and 400 nm period was formed on a Si surface using two-beam interference and dry etching. The TM transmission spectrum of the fabricated element was greater than 60% at the incident angle of θ = 40° (the angle between the incident direction and the perpendicular axis to the grating direction) in the 4–10 μm wavelength range. An extinction ratio of 22.2 dB was achieved at 2.5 μm wavelength. Additionally, results show that this polarizer has higher thermal resistance than that of commercial infrared polarizers. Therefore, this polarizer is effective for taking a polarized thermal image of high temperatures.

Two-way wavelength conversion was achieved for visible and infrared signal pulses by using a phosphorescent disk. When a visible (530 nm) or infrared (980 nm) laser beam was focused on the disk, absorbed photons created bright spots that emitted both visible and infrared phosphorescence (upconversion and downconversion). Although the phosphorescence lasted for 1 ms, a pulse signal of 1 MHz (1 μs period) was detected successfully by circulating the bright spots on the disk (a time–space conversion method). In comparison with downconversion, upconversion was easier to achieve for high-frequency signals, since the two-photon absorption process prevented overlapping of adjacent spots by restricting the phosphorescence spot size.

A mirror vibration induces a space rotation, and accordingly, phenomena in the time domain are converted to spatial distributions. This time-space conversion realizes high-speed measurements that exceed the operation limit of instruments. In this study, a time-resolved spectrometry was conducted by using slow optical devices, i.e., a continuous-wave laser diode, a CCD-based spectrometer (exposure time: 1 s), and a galvano-mirror (30 Hz). In comparison with pulsed lasers, the continuous-wave laser is advantageous for continuous integration of weak fluorescence. Experiments were conducted with fluorescent lanthanide solutions to examine the validity of this method.

When violet or green pulses were launched into an elastomer containing photochromic diarylethene, two competitive absorption bands emerged at around 400 and 520 nm. The violet pulses suppressed the former and enhanced the latter, whereas the green pulses induced the opposite reaction. Consequently, these signals self-formed their optical path in the elastomer (self-enhancement). By contrast, blue pulses exhibited either a self-enhancement or suppression characteristic depending on whether the elastomer had been irradiated by the violet or green signal before the blue signal transmission. Measurement of the transient spectra during the irradiation process revealed that the blue photons were absorbed by both 400 and 520 nm bands inducing two competitive photochromic isomerizations simultaneously.

Weak spontaneous emission and strong stimulated emission were switched reversibly by melting and freezing a polyethylene-glycol solution of rhodamine 6G, which exhibited a phase transition from transparent liquid to turbid solid.

Photo-degradation of organic dyes occasionally causes problems in microoptical devices, e.g., microfluidic or droplet lasers, since a strong optical power is concentrated in a small volume for the enhancement of the operation efficiency. Although lanthanide ions provide bleach-resistant fluorescence emitters, their absorption and emission efficiencies are so poor that they usually require a long optical path. Polyethylene glycol is a useful solvent that enhances both the absorption and emission efficiencies due to its turbid characteristic and its ligand effect. A polyethylene glycol solution of europium ions exhibited an 80-fold stronger fluorescence (613 nm wavelength) than an aqueous solution. In addition, solidification induced twofold enhancement of the fluorescence intensity due to the pump light (396 nm wavelength) confinement in a small volume.

Cu nanoparticles were fabricated by ablating a Cu plate in polysiloxane oil with laser pulses of 1.4 MW/mm 2 (wavelength: 532 nm, pulse width: 5 ns). Polysiloxane oil was useful to avoid oxidation and aggregation of Cu particles. Particle size of 2–20 nm was confirmed by TEM observation of fabricated samples. Solid materials containing Cu nanoparticles were also fabricated by curing polysiloxane at room temperature.

An electrostatically-tunable infrared filter was fabricated by constructing a Fabry–Perot interferometer with stacked silicon plates. Driving-voltage, which used to be ∼100 V with ordinary silicon plates, could be reduced to ∼30 V by decreasing plate thickness to 100 μm. Both theoretical simulation and bending test confirmed sufficient mechanical durability of these thin plates. Superimposition of a noise spectrum, which was caused by interference inside thin silicon plates, could be suppressed by polishing the plates into wedges. Consequently, pronounced interference peaks appeared at 12.6, 6.3, and 4.2 μm wavelengths, and they shifted to 9.8, 4.9, and 3.3 μm, respectively, by 30-V application.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles which is composed of six electromagnets and six displacement sensors and enables a 5-DOF magnetic bearing, has been developed. This paper deals with equations of motion of the MBW. In general, these equations are formulated in consideration of only the rotor imbalance. However, besides the imbalance, there are actually other disturbance factors in the magnetic bearing and the ordinary equations are difficult to simulate the actual disturbance properties of the MBW. In this paper, the more accurate equations of motion of the MBW are formulated in consideration of all disturbance factors of the MBW including property differences among six electromagnets. In addition, the accuracy of the proposed equations is verified by the coincidence of simulation and experimental results.

症例は84歳，女性．20年前より頸部に腫瘤を自覚していたが放置していた．2003年2月，転倒し右橈骨々折にて当院整形外科を受診した際に頸部腫瘍を指摘され当科紹介となった．腫瘍は最大径18cm大と巨大であったが，症状は腫瘍による腫瘤触知，頸部違和感のみで呼吸困難や嗄声などは認めなかった．頸部CT検査では甲状腺右葉の一部から発生した多結節癒合状の腫瘍で内部不均一であり，周辺組織を圧排していたが，周囲との境界は比較的明瞭であるため，切除可能と判断し外科的治療を行った．手術は甲状腺右葉切除を施行し，術後の病理組織診にて甲状腺濾胞癌の診断を得た．術後5年を経過した現在，無再発で外来経過観察中である．

症例は53歳，女性．2005年1月頃に右乳房腫瘤に気づいたが放置していた．その後，急速に増大し，疼痛を伴うようになり，右乳房の変形をきたすほどの巨大な腫瘤となったため，2005年10月当科を受診した．腫瘍は最大径15cm大，弾性硬で皮膚は発赤していた．手術は右乳房切除術を施行した．術後の病理所見にて乳腺間質肉腫と診断した．リンパ節転移や脈管侵襲は認めなかった．合併症なく術後経過は良好で，術後第10病日に軽快退院となった．退院3週間後に呼吸苦を主訴に再診した．胸部X線検査にて右胸水を多量に認め，胸部CT検査では右前胸壁に3cm大の再発巣を認めた．胸水細胞診にて異型細胞を認め，胸膜播種による悪性胸水と診断した．再入院後，右胸腔ドレナージを施行した．その後も胸水の排液は持続，再発巣も急速に増大し，術後第67病日に死亡した．

We fabricated infrared Fabry–Perot filters by stacking two wet-etched silicon plates. The silicon plates were etched in a KOH solution to 100 µm thickness to reduce the driving voltage, and were scratched before etching to suppress the interference inside the silicon plates. When a voltage was applied to the filter, the spacing between the plates changed due to an electrostatic force, which caused a shift in the interference peaks. When the voltage was increased from 0 to 50 V, an interference peak shifted from an 8.0 wavelength to a 4.1 µm wavelength, corresponding to the decrease in the spacing from 4.1 to 2.1 µm.

A terahertz (THz) wire-grid polarizer consisting of a micrometer-pitch Al grating on a Si substrate was fabricated by photolithography and wet etching. Extinction ratio (the ratio of TM and TE transmittances) was over 35 dB at 0.5 THz, and over 23 dB in the 0.5–3 THz range. At the Brewster's angle of Si (74°), TM transmission exceeded 90% in the 0.5–3 THz range. The fabricated polarizer had a higher extinction ratio than conventional free-standing terahertz wire-grid polarizers.

Infrared Fabry–Perot filters were fabricated by stacking two silicon plates etched in KOH solution. When we applied a voltage between the plates, the spacing between them was decreased by an electrostatic force, which caused a shift in interference wavelength. The silicon plates were etched to 34 µm thickness to reduce the driving voltage. When the voltage was increased from 0 to 20 V, the wavelength of the interference peak shifted from 7.9 to 5.5 µm, corresponding to the decrease in the spacing from 7.9 to 5.5 µm. The peak transmittance increased to ~90% by coating an antireflection film on the outer surface of the filter. This coating was effective in suppressing the interference inside the silicon plates, which created a complicated spectrum.

Fast-response infrared spectrometer was fabricated for spectral analysis of flowing gases. An infrared-transmitting AgI/Ag hollow fiber of 1 mm diameter was used as a flow cell to reduce both a sample volume and a sampling time. An infrared beam that passed the flow cell was diffracted by a grating, and was detected by a 256-channel PtSi sensor array. Transmission spectra of CH 4 and CO 2 gases were measured in the 3–5 μm wavelength range at 1/60 s intervals.

A Magnetic Bearing Wheel (MBW) with inclined magnetic poles is under development, which enables the 5-DOF magnetic bearing to be composed of six electromagnets and thus to reduce the size and the weight. This paper deals with the control method and the surface distortion compensation of the sensors and the magnetic poles of the MBW. In general, the control of electromagnetic force of magnetic bearing with inclined magnetic poles tends to be complex. Based on a geometric analysis of electromagnetic force and magnetic bearing force/moment, a synthesis of simple magnetic bearing controller is proposed, which utilizes redundant freedom of electromagnetic force in order to satisfy a certain restriction on the magnetically suspended system and to optimize bias electromagnetic force. Next, a compensation method of the surface distortion of sensors and magnetic poles, which induces force/moment disturbance of the MBW, is presented.

In some fiber optic sensors, effective noise reduction is achievable by modulating signal radiation at the fiber input end. A small durable modulator is required if a fiber probe is to be inserted in a narrow hazardous environment. The use of plasma absorption in semiconductors is helpful in the development of an all-optical compact modulator that is compatible with various hazardous environments. Since the carrier recombination time in Si (∼0.5 ms) is longer than that in other semiconductors, Si is suitable for the 10–1000 Hz modulation required for sensitive infrared detection. Infrared light modulation at 1 kHz was demonstrated in the 2–12 μm wavelength range by Nd:YAG laser irradiation. This modulation technique was used in infrared fiber optic thermometry, and it successfully eliminated the effects of fiber temperature variation, formerly a serious problem in conventional thermometry.

Acoustic manipulation of locomotive microorganisms, i.e., euglena and paramecia, was conducted by using ultrasonic standing waves of ∼3 MHz. Microorganisms were trapped at the intersections of the nodes in the two orthogonal standing waves and were transferred horizontally and vertically by the suitable ultrasonic frequency change. Aggregation of microorganisms was also observed in the process of the cyclic frequency change. The trapping efficiency depended on both ultrasonic power density and the activity of microorganisms. The effects of water temperature and illumination on their activity were evaluated by measuring the ultrasonic trapping efficiency.

Laser-assisted chemical etching was conducted for creating periodic textures on silicon surfaces. Silicon plates with the (111) surface orientation were immersed in an aqueous solution of potassium hydroxide, and a pulsed laser beam (532 nm wavelength, 5 ns duration, 10 pulse/s) was irradiated on their surface to promote anisotropic etching. The laser beam was patterned by using a glass capillary plate that contained a hexagonal array of micropores (10μm diameter, 12μm period). The focused beam projected the hexagonal image on the silicon surface, creating bright spots of 4μm period. During the laser irradiation process of 3 min, both laser-induced ablation and chemical etching took place at these bright spots. After stop of laser irradiation, the chemical etching progressed further, and consequently, a periodic array of triangular or hexagonal pits emerged on the silicon surface. The direction of the triangular pits changed by rotation of the silicon plate. When a silicon plate with the (100) surface orientation was used, diamond or rectangular pits were created on its surface. The mechanism of this polygonal texturing was explained by using the normal and intersecting vectors of the (100), (110), and (111) planes that exhibited different etching rates.

Dye molecules diffuse rapidly in a polydimethylsiloxane rubber that is swollen with toluene. This phenomenon is useful to create a durable photopolymer that self-heals its degraded optical function by replacement of damaged and fresh dye molecules. The lifetime extension was demonstrated by repeating photochromic reactions with dye-dispersed PDMS rubbers.