Takeshi Inoue

Purely gain‐coupled distributed feedback semiconductor lasers

We propose a new distributed feedback (DFB) laser structure in which almost pure gain coupling can be embodied in principle, without sacrificing low threshold operation. An analysis of coupling coefficients has revealed the condition for canceling index‐coupling component. Utilizing organometallic vapor phase epitaxy, we have fabricated GaAlAs/GaAs ridge waveguide distributed feedback lasers having this structure. Excellent single longitudinal mode oscillation independent of facet reflection has been obtained along with low threshold current. The single‐mode spectrum has exhibited distinctive characters of purely gain‐coupled DFB lasers.

Piezoelectric ceramic transformer operating in thickness extensional vibration mode for power supply

A new kind of multilayer piezoelectric ceramic transformer for switching regulated power supplies is described. This transformer operates in the second thickness extensional vibration mode. Its resonant frequency is higher than 1 MHz. Theoretical calculations are implemented using a distributed constant electromechanical equivalent circuit method. It is calculated that this transformer can operate with higher than 90% efficiency. A fabricated transformer is examined. PbTiO/sub 3/ family ceramics are used because of the large anisotropy between electromechanical coupling factors. Results indicate that the piezoelectric transformer has good resonant characteristics, with little spurious vibration, and exhibits 16 W/cm/sup 3/ power density with high efficiency at 2 MHz. A switching regulated power supply, applying the piezoelectric transformer, is built and examined.<<ETX>>

Fabrication and characteristics of gain-coupled distributed feedback semiconductor lasers with a corrugated active layer

A distributed feedback (DFB) semiconductor laser structure in which pure gain coupling can be realized is proposed. The fabrication procedure of this structure makes use of a special feature of organometallic vapor phase epitaxy. Lasers of this structure were fabricated to show the validity of the proposal. Coupling coefficients of DFB lasers were calculated considering the gain-coupling component. Using the results, a DFB laser was designed to obtain pure gain coupling. The parameters of the actual structure observed under a scanning electron microscope showed good agreement with those designed. Device characteristics predicted for purely gain-coupled DFB lasers were achieved. For greater gain coupling and lower threshold current operation, an optimization of the Al composition of the pattern-providing layer and the thickness of the active layer in the structure has been carried out. >

Step-Down Piezoelectric Transformer for AC-DC Converters

In this paper, a new piezoelectric transformer for AC-DC converters is presented. This piezoelectric transformer, with a multilayered construction in the thickness direction, operates in a fundamental contour-extensional vibration mode. Output impedance is designed to be low, approximately several tens of ohms. First, we simulated the design of the transformer using equivalent circuit method and finite element method (FEM) analyses. We calculated that the transformer could work with an eficiency higher than 95% and a gain of 0.4 at a resonant frequency of 140 kHz. Second, we fabricated a transformer of 14 mm length, 14 mm width and 5.8 mm thickness and examined it. It was found that the transformer exhibited a 0.4 gain and 96.3% efficiency at 135 kHz, when the temperature increase was 30°C. We applied the transformer to the fabrication of an AC-DC converter using a half-bridge zero voltage switching circuit, and examined the converter. It was found to achieve good line and load regulation, and the highest efficiency of 90% was obtained for Vin=80–120 Vac, Vout=13 Vdc, and Iout= 0.8–1.5 A.

Underwater low-frequency ultrasonic wave transmitter

Non-active columnar members are disposed on both sides of an active columnar member consisting of a piezoelectric ceramic material or a magnetically strainable material. Levers are connected to the active and non-active columnar members via first and second hinges. Convex shells are connected to the levers via third hinges. The displacement of the active columnar member is enlarged via the lever action, thereby enabling a miniaturized ultrasonic wave transmitter having high power capability.

Piezoelectric ultrasonic motor using longitudinal-torsional composite resonance vibration

A piezoelectric ultrasonic motor, which uses longitudinal and torsional composite vibration, is examined in order to obtain high torque characteristics with small diameter. Piezoelectric ceramic elements, oscillating in both longitudinal and torsional modes, respectively, are used as piezoelectric stiffened modes having high electromechanical coupling factors k/sub 33/ and k/sub 15/, respectively. It is found that the resonant frequencies for longitudinal mode and torsional mode could coincide with each other in the ultrasonic motor, according to finite element method analysis and experimental measurement. The motor operating in both resonant vibrations indicated good performance. The 20-mm diameter motor exhibited 4 kgfcm maximum torque, 450 r/min maximum rotational speed, 40% maximum efficiency, and quick responsiveness, within 2.5 ms.<<ETX>>

Zero-voltage-switching techniques and their application to high-frequency converter with piezoelectric transformer

This paper classifies the zero-voltage-switching, clamped-voltage (ZVS-CV) topologies for high-frequency switching dc-dc converters. These topologies are suitable for high-frequency operation because they can suppress the switching loss and voltage stress to the switching elements. In order to demonstrate this feature, we applied a ZVS-CV topology to the high-frequency dc-dc converter with a piezoelectric transformer which operates in megahertz frequency region. In our experiments, the efficiency of 77.8% at the switching frequency of 1.3 MHz was obtained.<<ETX>>

Tonpilz piezoelectric transducers with acoustic matching plates for underwater color image transmission

Tonpilz piezoelectric transducers with multiple acoustic matching plates are suitable for color image acoustic transmission, to achieve wideband low-ripple characteristics as well as high-efficiency high-power transmitting capability. The design method for the transducers was investigated on the basis of multiple-mode filter synthesis theory. For transducers with single, double, and triple matching plates, optimum specific acoustic impedances and lengths were calculated. Moreover, based on this design method, a 24 kHz array comprising nine identical transducers with single matching plates was built and evaluated. As a result, this array showed high-efficiency, low-ripple, and wideband characteristics. Excellent agreement between theoretical values and experimental results was obtained. A field test was carried out on color image transmission from a 3500 m sea depth, using the fabricated array, during which good color images were received.<<ETX>>

Tonpilz Piezoelectric Transducer with a Bending Piezoelectric Disk on The Radiation Surface

In recent years, it has become necessary to use wide-band signals in various kinds of signal processing and communication technology fields. One of these is the field of underwater acoustic technology, and therefore wide-band transducers are needed in this field. To address this need, we developed a Tonpilz piezoelectric transducer with a bending piezoelectric disk on the radiation surface of the front mass. This transducer was designed by providing a bending piezoelectric disk on the radiation surface of the front mass of a conventional Tonpilz piezoelectric transducer to enable it to generate in two resonance modes: the longitudinal vibration resonance mode and the bending vibration resonance mode of the bending disk. Coupling these two resonance modes makes it possible to achieve low-frequency transmission, and wide-band signals can be attained by adjusting the phase in the two modes. We obtained the optimum design dimensions of the transducer through analysis using the finite element method (FEM), and constructed a prototype based on the analysis. Experiments verified that the measured results for the prototype correspond well to the simulation results and that the bandwidth can be widened without changing the external size of the conventional transducer.

Piezoelectric ultrasonic motor using longitudinal-torsional composite vibration of a cylindrical resonator

A piezoelectric ultrasonic motor, which uses longitudinal and torsional composite vibration of a cylindrical resonator, was investigated. It was found that the resonant frequencies for longitudinal mode and torsional mode could coincide with each other in the cylindrical resonator, according to finite element analysis and experimental measurement. The motor using both resonant vibrations showed good performance. The 20-mm-diameter motor exhibited a 4 kgf-cm maximum torque, a 450-r.p.m maximum rotational speed, and a 40% maximum efficiency.<<ETX>>