Hironori Kumazaki

Tunable wavelength filter using a Bragg grating fiber thinned by plasma etching

We studied a tunable wavelength filter using a single-mode fiber Bragg grating with a cladding thinned by reactive plasma etching. Reflection wavelength shifts were demonstrated by controlling the effective refractive index or the period of the grating. When liquid paraffin was used for additional cladding on a thinned grating fiber of 19-/spl mu/m diameter, the shift rate of 0.055 nm//spl deg/C was obtained. In the case of applying the tension to the grating region, the shift rate was 3.4 nm/100 V for the fiber of 41-/spl mu/m diameter.

Photothermal vibration of fiber core for vibration-type sensor

Photothermal vibration of a quartz core of an optical fiber is described. A microcantilever rod comprised of the quartz core was fabricated by etching the clad layer from the optical fiber tip, and was vibrated photothermally using a laser diode. Frequency dependence of the vibration amplitude of the cantilever was measured for vacuum sensing. The resonance frequency decreased from 16.69 to 16.59 kHz with increase of the pressure from 100 to 102 Pa, and the resonance sharpness Q decreased from 2000 to 700 with increase of the pressure from 102 to 105 Pa.

Quadrature Mach?Zehnder interferometer with application in optical coherence tomography

A novel quadrature interferometer based on Mach–Zehnder configuration and a 3 × 3 fibre coupler is presented. Measurements showing instantaneous extraction of both real and complex parts of the interferometric signal are described. The features of this quadrature interferometric platform are discussed with a focus on signal-to-noise ratio and optical power handling.

Pressure dependence of resonance characteristics of the microcantilever fabricated from optical fiber

Abstract A quartz core microcantilever was fabricated from an optical fiber tip and was vibrated photothermally by laser diode light through the optical fiber. The vibration of the cantilever is stable and complicated adjustment of the optical system is not necessary. Pressure dependence of the resonance curve was measured for cantilevers of various sizes, and evaluated using a “string-of-beads” model for the quartz oscillator.

Micromachining of optical fiber using reactive ion etching and its application

If micromachining of an optical fiber with a three-dimensional structure could be performed, optical fibers would be more useful as devices with novel functions for communication instruments and sensors. The fabrication of a photon scanning tunnelling microscope (PSTM) fiber probe by wet chemical etching in a buffered hydrofluoric acid and micrometer-scale taps in a cladding by laser ablative chemical etching has been reported. However, a simple fabrication method for various configurations, such as lathe machining of optical fibers with high accuracy, has not been reported. For example, an optical fiber with some cladding in the middle region removed can be applied as a variable attenuator. In the case, the quantity of outgoing evanescent waves from the optical fiber depends on the type of material (or its position) surrounding the region from which the cladding has been removed. In this paper, micromachining of an optical fiber by reactive ion etching (RIE) and its application are discussed.

Temperature Dependence of Resonance Frequency of Shape-Memory Alloy Vibrated Photothermally.

The temperature dependence of the resonance frequency for a cantilever of a shape-memory alloy vibrated photothermally is described. The temperature coefficient of the resonance frequency of the alloy with memory for shape recovery was positive (2.0×10-2/° C) at a temperature near the martensitic transformation, in contrast with it being negative (-2.2×10-3/° C) for the alloy without memory. The technique of using one laser for both excitation and detection was adopted for determining the resonance frequency of the photothermal vibration.

Beam scanning system for large tilt angle ion implantation

Abstract A trench structure has been adopted to a VLSI device such as a 4M DRAM. To implant effectively on the trench wall surface, it is necessary to vary the tilt angle over a large range, for example from 0° to 60°, during implantation. A unique electrostatic scan system has been developed for such an application. According to the several input parameters, such as tilt angle and beam energy, the system can automatically generate a scanning wave form ensuring dose uniformity over the wafer.

Sweep Uniformity Control System in the NISSIN NH-20SP

The NH-20SP medium current parallel ion implanter features in situ parallelism monitoring, in situ uniformity monitoring and in situ uniformity controlling. This paper describes the hardware and software of sweep uniformity control system which is performing these functions.

Mechanical stress sensors using micromachined grating fibers

We discuss mechanical stress sensors based on fiber Bragg gratings (FBGs) micromachined by anisotropic reactive ion etching (RIE) using CF4 plasma. Locally thinned FBGs have the potential to be used as sensitive strain sensors whose sensitivities increase with decreasing measurement range. The center reflection wavelength shift rate of an etched and thinned grating (thinned grating length: 2.0 mm; thinned diameter: 15 μm; total grating length: 10.0 mm) was approximately 15 times greater than that of a conventional unprocessed FBG. The difference in the center reflection wavelengths of thinned and unetched grating regions could be used to counteract changes in the surrounding temperature. On the other hand, a single FBG with an asymmetrical cross section can detect the degree of curvature and the bending direction. The center reflection wavelength shifted by 0.4 nm at 1550 nm on bending that imparted a radius of curvature of ±127 mm.