Hirochika Nakajima

Crosstalk characteristics of Ti-LiNbO 3 intersecting waveguides and their application as TE/TM mode splitters

Crosstalk characteristics of an intersecting waveguide are presented. Two straight channel waveguides which intersect at an angle of a few degrees on y -cut LiNbO 3 were fabricated by in-diffusion of Ti. Experimental results show that the crosstalk characteristics are determined by the refractive index change profile and the geometry of intersection associated with guided wave modes. In a special case, a TE/TM mode splitter was obtained by using the intersecting waveguide which provides adequate anisotropy by the change in refractive indices. Splitting ratio was 17 and 14 dB for the TE and TM modes, respectively.

Practical method of waveguide-to-fiber connection: direct preparation of waveguide endface by cutting machine and reinforcement using ruby beads

We propose and demonstrate new practical methods of waveguide end fabrication and fiber attachment for Ti:LiNbO(3) waveguides. We fabricated waveguide endfaces with a cutting machine, which simplifies the manufacture of waveguide devices and provides a low excess loss of 0.3 dB or less. Our proposed fiber attachment method features fibers that protrude slightly from the reinforcement. It provides easy alignment, low excess loss (<0.1 dB), high strength (>600 gf), and high thermal stability (-10 to 60 degrees C). We also developed an easy way to reduce the backreflection from the joint without using anti-reflection coating. Instead, a tapered hemispherical end fiber and an angled waveguide endface are used. Backreflection is easily reduced to less than -30.

Nonmechanical optical switch for single-mode fibers

This paper introduces a bistable nonmechanical optical switch for single-mode optical fibers. A l-input/2-output device for the l-microm wavelength range, the optical losses of the switch are independent of the polarization state in the input fiber. The insertion losses for the optical signal from the input fiber to the output fiber are 1.4 dB and the crosstalks are -28 dB at 1.3-microm wavelength. Switching is performed by a 20-microsec one-shot pulse with a maximum current of 500 mA. The voltage to switch the optical path is 5 V.

Magnetooptical 2×2 switch for single-mode fibers

An optical switch for single-mode fibers is presented in this paper. A novel polarizing prism is introduced to make the 2 input, 2 output optical switch insertion loss low and independent of the polarization state of the input fiber. This switch operates by one electric pulse with a voltage of only 2.5 V and a current of 35 mA. The insertion loss was 1.2 dB, its fluctuation for different input polarizations was within 0.03 dB, and the far-end crosstalk was −26 dB at a wavelength of 1.3 μm. The shock resistance of the switch was confirmed during an acceleration of 100 g.

Event-related magnetic fields at latencies of over 400 ms in silent reading of Japanese Katakana meaningless words.

Event-related magnetic fields (ERFs) were recorded when subjects were presented with meaningless readable words or unreadable words. The ERF averages for readable words and those for unreadable words showed a large difference at latencies of over 400 ms. The equivalent current dipoles were obtained only for readable words, and were located near the cingulate gyrus and the supplementary motor area whose functions are considered to be related to attention and motor planning.

Crosstalk Characteristics of Ti-LiNbO/sub 3/ Intersecting Waveguides and Their Application as TE/TM Mode Splitters

Crosstalk characteristics of an intersecting waveguide are presented. Two straight channel waveguides which intersect at an angle of a few degrees on y-cut LiNbO/sub 3/ were fabricated by in-diffusion of Ti. Experimental results show that the crosstalk characteristics are determined by the refractive index change profile and the geometry of intersection associated with guided wave modes. In a special case, a TE/TM mode splitter was obtained by using the intersecting waveguide which provides adequate anisotropy by the change in refractive indices. Splitting ratio was 17 and 14 dB for the TE and TM modes, respectively.

Permalloy film for single‐level detector with high sensitivity

The use of single‐level circuit has simplified the fabrication process. A thick film detector, however, has weak points; it has a low detection efficiency due to the large demagnetizing field and unfavorable noise is inherent in it. The authors study the magnetoresistive characteristics of permalloy films and find out the detectors with high senstitivity, selecting the appropriate evaporation conditions. The significant results are as follows. (1) The large detection voltage is obtained from those elements whose magnetic easy axis deviates from the shape anisotropy direction, which serves to reduce the effective anisotropy field. (2) This angle of deviation α is increased with the raising of the substrate temperature and with the lowering of the evaporation rate. For example, α=60° at 310°C, 3AC, 3A/sec, and α=0° at 250°C, 10A/sec. (3) Detection performances are investigated on the 30‐column serpentine detector using 3 μm stripe domain width of (YGdYb)3(GaFe)5012 with a 4π Ms of 260 Gauss. The signal volt...

Low-drive-voltage Ti:LiNbO 3 Mach-Zehnder modulator using a coupled line

A Ti:LiNbO3 Mach-Zehnder modulator with an asymmetric traveling-wave electrode has been studied for use as a high speed external modulator because of its low chirp and wide bandwidth.1 The overly high drive voltage prohibits practical use, however. Our attempts to reduce the drive voltage by, for example, using two traveling-wave electrodes,2 have met with problems, such as the interaction of microwaves.

Si 1-x Ti x O 2 guided-wave connecting circuits grown by magnetron sputtering

Connection between optical active/passive elements and libers is very important in practical device packaging. Multichannel connection is very hard if we use liber array direct coupling to multichannel elements such as laser diode arrays, matrix switches, and grating filters. Minford et al. reported a Ti:LiNbO3 seven-channel waveguide concentrator between a single-mode fiber array and a grating filter with a GRIN lens.1 However, Ti:LINbO3 has a relatively low ΔN and needs a large bending radius and connection length to expand the interchannel distance with low insertion loss. To realize compact connecting circuits, a large ΔN waveguide is needed.