Takashi Katagiri

Takashi Katagiri
University of Toyama | U Toyama · Department of Intellectual Information Engineering

Doctor of Engineering

About

70
Publications
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525
Citations

Publications

Publications (70)
Article
For gas analysis systems based on terahertz time-domain spectroscopy (THz-TDS), relatively complex systems have been proposed to enhance the sensitivity to measure small amounts of gas. This paper proposes a simple system comprising a hollow optical fiber with an inner dielectric layer as a low-volume and long-path gas cell THz-TDS-based gas analys...
Article
Full-text available
A real-time gas monitoring system based on optical absorption spectroscopy is proposed for localized carbon dioxide (CO2) measurement in respiratory tracts. In this system, a small gas cell is attached to the end of a hollow optical fiber that delivers mid-infrared light with small transmission loss. The diameters of the fiber and the gas cell are...
Article
The configuration of a gas analysis system using the combination of a single-wavelength quantum cascade laser and a hollow-optical-fiber gas cell was optimized to improve measurement sensitivity. On the basis of theoretical calculation, a 6-m looped fiber gas cell was introduced into the system to more sensitively measure the concentration of nitri...
Article
An acoustic probe based on a Fabry–Perot interferometer composed of a polymer film attached to the end of an optical fiber was designed and fabricated for an endoscopic, all-optical photoacoustic imaging system. The finesse of the interferometer was improved by forming a half-mirror at the end of the fiber and a partial reflection mirror on the out...
Article
The behavior of terahertz pulse propagation in hollow optical fibers is investigated using terahertz time-domain spectroscopy. The transmission loss spectra of hollow optical fibers made of a flexible polycarbonate tube with an inner silver layer are measured at the wavelength range from 0.2 to 3 THz. The spectra of fibers with an inner diameter of...
Article
Full-text available
A breath analysis system based on ultraviolet-absorption spectroscopy was developed by using a hollow optical fiber as a gas cell for real-time monitoring of isoprene in breath. The hollow optical fiber functions as an ultra-small-volume gas cell with a long path. The measurement sensitivity of the system was evaluated by using nitric-oxide gas as...
Article
A bundle composed of 245 anti-resonant glass hollow optical fibers with a total diameter of 1 mm and fiber core diameter of 60 μm is fabricated for endoscopic infraredthermal imaging. The bundle fiber shows low losses in the wavelength range of 3 to 4 μm owing to the anti-resonant effect of the thin glass wall. An image resolution of around 420 μm...
Article
Full-text available
A photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers is proposed for endoscopic diagnosis. In this system, a bundle of 127 hollow-optical fibers with an inner diameter of 100 μm was fabricated. The total diameter of the bundle was 2.1 mm, and the minimum bending radius was around 10 mm. Owing to the small numer...
Conference Paper
We propose a photoacoustic imaging system composed of a flexible bundle of thin hollow-optical fibers that enables endoscopic diagnosis. The hollow-fiber bundle involves 37 fibers with an inner diameter of 100 μm and the total diameter of the bundle is 1.2 mm. A laser beam for photoacoustic excitation is scanned at the input end of fiber bundle and...
Article
A mid-infrared attenuated total reflection (ATR) spectroscopy system employing hollow optical fibers and a trapezoidal multi-reflection ATR prism has been developed to measure blood glucose levels. Using a multi-reflection prism brought about higher sensitivity, and the flat and wide contact surface of the prism resulted in higher measurement repro...
Conference Paper
Rugged hollow fibers for FT-IR remote spectroscopy are fabricated by all-liquid phase technique. A buffer film coated on the inside of the silica-glass capillary protects the tube from acid solution and improves the mechanical strength.
Article
Systems for infrared reflectance imaging are built with an FT-IR spectrometer, hollow optical fibers, and a high-speed infrared camera. To obtain reflectance images of biological samples, an optical fiber probe equipped with a light source at the distal end and a hybrid fiber probe composed of fibers for beam radiation and ones for image detection...
Article
A Raman imaging system which combined a hollow fiber bundle and a direct imaging technique was constructed for high-speed endoscopic Raman imaging. The hollow fiber bundle is fabricated by depositing a silver thin film on the inner surface of pre-drawn glass capillary bundle. It performs as a fiber optic probe which transmits a Raman image with hig...
Article
We present tube-leaky fiber with microstructured glass supports as a hollow core microstructured optical fiber. Attenuation constants of tube-leaky fibers are derived by using a ray optic method and designed the wall thickness of the fibers for Er:YAG laser which is often used for medical applications. From the loss measurements of Er:YAG laser, th...
Article
A flexible fiber probe for surface-enhanced Raman scattering (SERS) was fabricated by forming gold nanostructures on a ball lens mounted at the distal end of a hollow optical fiber. Two different methods were used to form the gold nanoparticles. In the photochemical deposition, easily fabricated probe indicated good sensitivity, but low reproducibi...
Article
A tube-leaky fiber that consists of only dielectric thin-film tubing for delivery of Er:YAG laser light is presented. The tube-leaky fiber confines light in the airy core when the film thickness is properly chosen for target wavelength. Transmission properties of the fibers are derived by using a ray optic method and designed the optimum wall thick...
Article
Low-loss hollow waveguides with a multiple dielectric layer are designed and fabricated for use in cavity ring-down spectroscopy (CRDS). Calculations of the waveguide design revealed that hollow waveguides for infrared CRDS system need to have transmission loss of 0.1 dB/m or less. We fabricated rectangular hollow waveguides with multiple dielectri...
Article
A laser-induced breakdown spectroscopy (LIBS) system based on a hollow optical fiber was developed. The fiber is used for both the delivery of the excitation laser and detection of emission spectra. The fiber probe enables the measurement of unexposed sample surfaces by inserting or stabbing the probe into a sample. The feasibility of the LIBS syst...
Conference Paper
Low-loss hollow waveguides with multiple dielectric layer are designed and fabricated for use in cavity ring-down spectroscopy. The waveguides are composed of four glass strips with dielectric multilayer that are deposited on the surface in advance. Experimental results show that the waveguides with double dielectric layers have lower losses at a t...
Article
We optimized the configuration of a hollow-fiber gas cell used in a Fourier-transform infrared spectroscopy system for quantitative analyses of low-concentration gas components with small sample volume. Numerical calculation shows that the signal-to-noise ratio (SNR) of this measurement system is maximized in a condition dependent on a fiber's bore...
Conference Paper
Guiding mechanism of tube-leaky fibers composed only of a dielectric thin wall is explained by ray-optic method. The tube-leaky fiber supported by microstructured glass is fabricated and the loss at 2.94-μm wavelength was 0.87dB/m.
Article
To develop a thin and flexible hollow waveguide for terahertz (THz) waves that can be applied to endoscopic applications, a new (to our knowledge) fabrication method is proposed in which thin polymer tubing is first drawn and then a silver layer is formed on the outside of the tubing. By using this method, a thick dielectric layer, which was diffic...
Article
A spectral imaging system consisting of a Fourier transform-infrared spectrometer, a high-speed infrared camera, and a bundle of hollow-optical fibers transmitting infrared radiation images was constructed. Infrared transmission spectra were obtained by carefully processing multiple interferograms taken by high-speed photography. Infrared spectral...
Article
Flexible fiber bundles for image transmission are fabricated by use of hollow optical fiber. The fiber bundle was fabricated by the well-known stack-and-draw technique, and coated silver film as reflection layer on the inner surface. In this report, we describe the result of Raman spectral imaging using fabricated bundle.
Article
A spectral imaging system based on a bundle of hollow optical fibers transmitting infrared radiation image is constructed. The system consists of an FT-IR spectrometer and a high-speed infrared camera and infrared transmission spectra are obtained by carefully processing multiple interferograms. It is shown that infrared spectral images of a variet...
Article
The flexible fiber optic probe for laser trapping Raman spectroscopy is developed to analyze single bio-particles in vivo. The probe consists of the hollow optical fiber and TiO2 micro-lens. Red blood cell and yeast are stably trapped by the fabricated probe. The Raman measurement of PMMA particle having 10 μm diameters is also demonstrated.
Conference Paper
Fiber-optic Raman tweezers for molecular analysis of bio-particles in turbid media is proposed. The Raman tweezers consists of a single hollow optical fiber and a specially designed trapping lens mounted at the fiber tip. Raman spectra of polystyrene particles dispersed in NaCl aqueous solution are observed.
Conference Paper
The highly sensitive Raman cell based on the hollow optical fiber that is suitable for the real-time breath analysis is reported. Hollow optical fiber with inner coating of silver is used as a gas cell and a Stokes light collector. A very small cell whose volume is only 0.4 ml or less enables fast response and real-time measurement of trace gases....
Article
Full-text available
Er:YAG and Ho:YAG laser beams were combined to irradiate hard tissues to achieve highly efficient ablation with low laser power. The delay time between pulses of the two lasers was controlled to irradiate alumina ceramic balls used as hard tissue models. With optimized delay time, the combined laser beam perforated the sample 40% deeper than indepe...
Article
A fiber-optic probe based on a hollow optical fiber was developed for highly-sensitive remote-Raman measurements of particles in solution. A lens mounted at the distal end of the fiber was optimally designed to suppress the spherical aberration and maximize the numerical aperture by the ray-optics method, and fabricated by polishing a SrTiO3 ball o...
Article
A compact Raman cell based on the hollow optical fiber for highly sensitive breath analysis is reported. A polycarbonate tube-based hollow optical fiber with inner coating of silver is used for both a gas cell and a Stokes collector. An excitation laser light at 532 nm is launched into the cell filled with analytes and the Stokes light collected in...
Article
A hollow optical-fiber probe for infrared attenuated total reflection (ATR) spectroscopy is developed. A newly designed ATR prism, optimized for use with hollow optical fibers, is proposed. Results from preliminary experiments show the potential uses of the probe in clinical applications. The probe is appropriate for in vivo applications because it...
Article
A silica-core Bragg fiber surface-plasmon resonance (SPR) sensor with high design flexibility has been developed for refractive index measurement. In this geometry, an HE11-like Bragg fiber core mode is designed to excite the surface plasmonic wave. It is shown that reduction of core size enables measurement of refractive index significantly lower...
Article
Raman spectra of brain tissues of live mice and rats were successfully obtained using a miniaturized Raman probe. The use of a ball lens hollow fiber Raman probe and a background-free electronically tuned Ti:sapphire laser enabled the measurement of high-quality Raman spectra in the fingerprint region and high-wavenumber region at exactly the same...
Article
A micro Raman probe (MRP) with a 600 microm diameter, which we previously reported as the narrowest achieved to date, was further improved by introducing high-quality optical filters and a collecting lens at the tip. We fabricated the MRP with a high collection efficiency, a wider collection wavelength, and a high signal-to-noise ratio. We compared...
Article
A broadband terahertz time-domain spectroscopy (TDS) system for frequencies of up to 15 THz, including the phonon resonance frequency range, has been developed using a transferred thin-film photoconductive switch (PCS) detector. The thin-film PCSs, based on low-temperature-grown GaAs, were fabricated using epitaxial layer transfer onto high-resisti...
Article
Living pancreatic cancer tissues grown subcutaneously in nude mice are studied by in vivo Raman spectroscopy and autofluorescence imaging. Comparing the same point spectra of alive pancreatic cancer tissue to that of the dead tissue, it is found that they are different each other. The results suggest that the spectral changes reflect the protein co...
Article
A ball lens mounted hollow optical fiber Raman probe (BHRP) consisting of a single hollow optical fiber (HOF) and a micro-ball lens was developed for performing a high axial resolution and high-sensitivity remote Raman analysis of biomedical tissues. The total diameter of the probe head is 640 microm. The BHRP is useful in the measurement of thin-l...
Article
A ball lens hollow-fiber Raman probe (BHRP) is a powerful tool for in vivo nondestructive subsurface analysis of biomedical tissues in a living body. It has confocal-like optical properties, but its collection volume is rather large in comparison with that of a conventional confocal Raman system. Therefore, the obtained Raman spectra have contribut...
Article
Living pancreatic cancer tissues grown subcutaneously in nude mice are studied by in vivo microscope Raman spectroscopy. Comparing the spectra of living pancreatic cancer tissue to that of the dead same tissue, it is found that they are different each other. In the subtraction spectrum, Raman bands observed at 937, 1251, 1447 and 1671 cm-1 are appe...
Article
Full-text available
Hollow optical fiber probes are used for remote Raman and infrared spectroscopy. Preliminary experiments using these probes are performed, and the results of the experiments show that the hollow fiber probes are useful for endoscopic measurement of Raman and infrared spectroscopy. As regards to Raman spectroscopy, a hollow fiber probe with a ball l...
Article
Two types of hollow fiber-optic probes are developed to measure the in vivo Raman spectra of small animals. One is the minimized probe which is end-sealed with the micro-ball lens. The measured spectra reflect the information of the sample's sub-surface. This probe is used for the measurement of the esophagus and the stomach via an endoscope. The o...
Article
To produce long and flexible hollow optical fibers for midinfrared lasers at a low cost, hollow fibers are fabricated by using a glass drawing technique. When the wall thickness of the glass tube is properly designed and controlled, the fiber shows a low loss at a desired wavelength. By applying pressure into the tube preform, the glass capillary w...
Chapter
In vivo measurements of Raman spectra have been performed at the gastroesophageal epithelia of living rats by combining fiber-optic Raman spectroscopy system with an available endoscope unit for experimental animals. In our system, the endoscope worked well for a navigator with a probe channel, imaging and lighting fibers. Demonstrating in vivo Ram...
Article
Silica-core Bragg fibers supporting the single HE<sub>11</sub> mode are proposed for fiber devices including compact nonlinear devices and dispersion control components. Fibers are fabricated by forming a dielectric multilayer on the outside of a conventional single-mode fiber, which is partly redrawn to a small diameter. Bragg guidance over a broa...
Article
A hollow optical fiber Raman probe equipped with a ball lens is developed to study the stomach cancer. The probe generates little Raman scattering or fluorescence noise because the HOF confine light into the air core. In order to maximize the collection efficiency and the spatial resolution, material and size of the ball lens is optimized. The tota...
Article
A confocal Raman probe based on a silver hollow optical fiber is developed to apply in remote optical biopsy via a micro-endoscope. The probe consists of a single hollow optical fiber delivering both the excitation and the Raman scattered light, and a confocal end unit attached at the distal end of the fiber. We demonstrate a high spatial resolutio...
Article
Development of the optical biopsy system for experimental small animals is in progress. A prototype of the system which consists of a miniaturized gastro endoscope unit and Raman probes has been completed by now. The system is developed to study a gastric cancer rat model. The endoscope is 2.5 mm in diameter and is equipped an imaging bundle fiber,...
Article
We demonstrate the possibility of confining light in a submicron silica core by introducing a Bragg multilayer cladding. 1 mum-core Bragg tapers with mode field diameters about 1.1 mum for 850 nm wavelength are successfully fabricated by a sputtering technique combining with tapering method using a traveling burner. Simulation of the mode intensity...
Conference Paper
Silica-core Bragg fibers with a diameter below 10 μm are fabricated to achieve single-mode transmission. The core of the fiber is drawn from a conventional single-mode fiber and multilayer cladding is formed on the outside by sputtering deposition of Si and SiO<sub>2</sub> layers. Bandgap guidance over a broadband wavelength range and the mode prof...
Article
Hollow glass fibers for delivery of mid-infrared lasers are drawn from a glass-tube preform to produce a long and flexible hollow fiber at low cost. A silver film is coated on the drawn glass tube with a wall thickness as small as 9.1 μm. A Pyrex-glass hollow fiber with an inner diameter of 340 μm and a length of 42 cm shows a loss of 3.0 dB for Er...
Article
Hollow glass fibers for delivery of mid-infrared lasers are drawn from a glass-tube preform to produce a long and flexible hollow fiber at low cost. A silver film is coated on the drawn glass tube with a wall thickness as small as 9.1 mum. A Pyrex-glass hollow fiber with an inner diameter of 340 mum and a length of 42 cm shows a loss of 3.0 dB for...
Article
Techniques for coating hollow glass fibers with layers of silver and cyclic olefin polymer have been developed for low-loss delivery of infrared laser light as well as a visible pilot beam. They have yielded losses of only 0.2 dB/m for Er:YAG and CO2 laser light and only 0.7 dB/m for red LD laser light. Debris is kept from entering the hollow outpu...
Article
A new technique for fabricating a photonic bandgap fiber is proposed. A multilayer Si--SiO2 film is deposited upon a silica glass fiber, and a clear bandgap is observed in the loss spectrum. The properties of the bandgap are easily controlled by adjustment of the thickness and the refractive index of the multilayer film.
Article
A new fabrication technique of a photonic bandgap fiber is proposed. The fiber involves dielectric multilayer deposited by sputtering technique and the bandgap property is easily controlled by thickness and index of the multilayer.
Article
Hollow glass fibers for delivery of mid-infrared lasers are drawn from a glass-tube preform to produce a long and flexible hollow fiber at low cost. To utilize the interference effect of the thin glass wall, the wall thickness is controlled by the drawing speed. A Pyrex-glass hollow fiber with an inner diameter of 280 micron and a wall thickness of...
Article
Infrared hollow waveguides utilizing a dielectric multilayer are examined by use of a photonic bandgap theory. It is shown that, in the waveguide consisting of quarter-wave film stack, the act of covering the dielectric films with a metal layer is effective in the reduction of the number of film layers. To verify the effect of this design, we fabri...
Article
Hollow glass fibers for delivery of mid-infrared lasers are drawn from a glass-tube preform to produce a long and flexible hollow fiber at low cost. To utilize the interference effect of the thin glass wall, the wall thickness is controlled by the drawing speed. A Pyrex-glass hollow fiber with an inner diameter of 280 mum and a wall thickness of 9....
Article
Transmission properties of hollow waveguides utilizing dielectric multilayer are examined by using a photonic bandgap theory. Theoretical results show that, in the waveguide having quarterwave film stack, a large number of films is necessary to obtain low loss property. It is shown that covering the dielectric films with a metal layer is effective...

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