The fields in the junctions between straight and curved rectangular waveguides are analyzed by using the method of separating variables. This method was succeeded because the authors developed the method of numerical calculation of the cylindrical functions of complex order. As a result, we numerically calculate the reflection and transmission coefficients in the junctions in various situations, and we compare these results with the results by the perturbation method and with the results by Jui-Pang et al.

After a bend structure has been obtained through application of an appropriate voltage, a pi-cell exhibits one of two stable structures: a bend structure if the applied bias is above a certain threshold ( 2 V), and a twist structure at a lower voltage. For use in an optical device, the pi-cell must be operated with the bend structure. It was found, however, that when the bias is switched quickly to a level lower than the threshold, a metastable structure exists for a few hundreds of milliseconds before relaxing to a twist structure. From dynamic optical transmittance analysis, this structure is considered to have a bend configuration. The temporary bend structure persists at lower voltages because it takes a while to initiate an energy redistribution from the bend structure to the twist. This is considered as a novel physical state, and is called a "dynamic bend structure. " It enables the pi-cell to be operated even if the bias is below the threshold voltage, provided that the device is biased at higher voltages for a fraction of each cycle to retain the bend structure.

In order to examine the validity of Mott-Schottky model at organic/metal interfaces, the position of the vacuum level of N,N'-bis(3-methylphenyl)-N,N'-diphenyl -[1,1'-biphenyl]-4,4'-diamine (TPD) film formed on various metal substrates (Au, Cu, Ag, Mg and Ca) was measured as a function of the film-thickness by Kelvin probe method in ultrahigh vacuum (UHV). TPD is a typical hole-injecting material for organic electroluminescent devices. At all the interfaces, sharp shifts of the vacuum level were observed within 1 nm thickness. Further deposition of TPD up to 100 nm did not change the position of the vacuum level indicating no band bending at these interfaces. These findings clearly demonstrate the Fermi level alignment between metal and bulk TPD solid is not established within typical thickness of real devices.

Macrobending characteristics of a newly developed hetero-core splicing sensor is investigated from the viewpoint of the practical use intended both for relatively large distortion monitoring and for liquid adhesion detection. The hetero-core sensor can be simply fabricated by fusion splicing of a hetero-core fiber portion as short as approximately 5 mm in length, which is inserted in a typical low-transmission-loss single mode fiber with a 9-µm core diameter for the wavelength of 1.3 µm as a fiber network line. Two types of the sensor are typically realized in terms of the core diameters of 3 and 5 µm for the inserted hetero-core portion which are referred to as 9-3-9 and 9-5-9 types, respectively , with showing their distinct bending loss characteristics. This paper deals with the explorative applications of the two types of hetero-core sensors in which a bending-to-linear displacement converter and a liquid adhesion sensor are successfully examined using a 9-5-9 structure with its low insertion loss and a cladding interactive 9-3-9 structure with its high sensitivity, respectively. The low-insertion loss 9-5-9 sensor has shown the capability of monitoring millimeters-order distortion in low transmission loss fiber networks. On the other hand, the 9-3-9 type has found to be a prospective sensor for liquid adhesion detection. Operational mechanisms for these two sensors are also discussed in terms both of optical leaks occurring at the hetero-core interfaces and of the build-up of cladding modes which might interrogate the outer cladding boundary conditions of the hetero-core sensor.

We investigated the reflection of light caused by sharp bends in optical fiber experimentally. The position distribution of reflection power was measured using an OTDR and an OLCR. We found that the reflection power increased linearly as the logarithm of the bending loss increased, which agrees with expectation from a simple theoretical model. We believe that the light we observed was part of the leaked light, which was reflected between the primary and secondary coatings.

We propose and experimentally confirm two approaches to improve the sensitivity of the H-type piezoelectric crystal gyroscope of LiTaO3. One is to adjust the resonant frequencies of the fz mode through additional mass control; the other is to change the driving mode from fx mode to fz mode, while the driving frequency is the resonant frequency of the fx mode. The sensitivity of the unit driving voltage is almost the same, but the threshold driving voltage level may increase more than 1,000 times, because it is far from the mechanical resonance. The high sensitivity of 0.11 pC (deg/sec) was obtained at a driving voltage of 30 Vpp.

Characterization of a mitered, a squarely cut, and a circular E-plane bend in rectangular waveguide is implemented by combining the port reflection coefficient method and the mode-matching method. Based on the port reflection coefficient method, the two-port waveguide bend is converted to a one-port structure comprised of cascaded waveguide step-junctions. After solving the reflection coefficient caused by these waveguide step-junctions using the mode-matching method, the desired scattering parameters of the bend are obtained readily. Convergence properties of the calculated numerical results are validated. Influences of the mitered, the squarely cut, and the circular part of the bend on the scattering parameters are investigated, and the optimal design dimensions for realizing wide-band and low return loss bends are found. Based on the optimal compensation dimension, an E-plane waveguide circular bend is fabricated and tested. The measured result agrees well with the theoretical prediction, and a full-band matched bend is practically realized.

A model for estimating the bending loss of 1.3 µm zero-dispersion single-mode fibers at 1.58 µm from the value at 1.55 µm is investigated experimentally and theoretically. An approximated equation for estimating the bending loss ratio of 1.58 µm to 1.55 µm is proposed, which provides good agreement with the experimental results.

This paper presents a theoretical study on transmission properties of bent optical waveguides of uniaxial anisotropic material. The waveguiding structure consists of two parallel straight slab waveguides connecting by an oblique section. By arranging the direction of the optical axis in the oblique section so that the wave normal always points to the same direction throughout the waveguiding structure, low loss transmission can be realized. The analysis of wave propagation through the structure is based on the finite difference beam propagation method. Numerical results indicate that by optimally arranging the direction of the optical axis in the oblique section power coupling coefficients better than 95% can be obtained for any tilt angle of the oblique section when the tilt angle is smaller than 2 degrees. Some field distributions are also presented along the waveguiding structure.

Transmission characteristics of CPW bends having various curvatures and a fixed bend angle were measured. It was found that the transmission level shows dips at some particular frequencies, and that the dips are less pronounced as the radius of curvature becomes larger.

Pure bend loss of a fiber with a trench section is calculated by the alternating-direction implicit finite-difference method. The dependence of the loss on the trench location is evaluated. The mechanism of the oscillatory behavior of the loss is discussed in terms of a modal approach in a dielectric slab waveguide.

Optical waveguides are one of the key devices for photonic integrated circuits considered to be one of the candidates for optical interconnects. In particular lossless bend type waveguides are necessary to integrate different optical devices monolithically. In this paper, we report on the bending loss characteristics of the multi-quantum well bend waveguide with respect to the bend radius and lateral optical mode confinement. We show that to decrease the bending loss to less than 0.5 dB, it is necessary to increase either the confinement or the bend radius. For an example, when the confinement is around 85%, the bend radius should be more than 2 mm. We also show the application of the S-bend waveguides to directional coupler type optical switch.

This report will present an expression for the mechanical behavior of a drum-wound dual coated fiber and an analytical expression for the microbending loss in single mode dual coated fibers. These analytical expressions are then compared with experimental drumwinding microbending loss results to determine their validity.