bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and characterizations of Al12 W intermetallic compound film by Co‐sputtering
Authors: Sasaki Katsutaka , Noya Atsushi
Published: July 2007

An Al12W intermetallic compound film was formed by the co‐sputtering method for the development of Si‐LSI metallization technology. The condition to form a stoichiometric Al12W film, its electrical properties and surface characterizations were investigated. As a result, when a film deposited on an unheated substrate was annealed at a temperature above 400d̀C, it recrystallized and became a stoichiometric Al12W intermetallic compound.

The resistivity and temperature coefficient of resistance for an Al12W intermetallic compound film were 45 μω‐cm and 800 ppm/d̀C, respectively. Since the film resistivity is low compared with those of many other intermetallic compounds, it is expected to be useful as metallization material for an Si‐LSI. When the film is exposed to air, Al atoms segregate and become oxidized, resulting in the formation of a thin Al2O3 formed is at most 100 Å even after annealing in air at 440d̀C, the surface oxide layer is expected to be a passivation layer.
Boundary‐element method analysis of light‐beam scattering and the sum and differential signal output by DRAW‐type optical disk models
Authors: Kojima Toshitaka , Ido Jun
Published: July 2007

This paper assumes a simple model for the DRAW (direct‐read/after‐write) optical disk using a Te‐alloy recording medium. The scattering of the light‐beam by the pit or boss of arbitrary shape on the boundary of three‐layered dielectrics is analyzed by the boundary‐element method. The sum and the differential signal output characteristics of the two‐split‐type optical detector also is discussed. The results of simulation are shown for the effect of the adjacent pit in the square and V‐shaped pregrooved models, the dependencies of the sum and the differential signals on the tracking error, and the dependencies of the sum and the differential signals on the pit depth, when the signal recording pit is provided in the two types of pregrooved models.
Noise characteristics of NbN nanobridge dc SQUIDs fabricated by field emission technique
Authors: Nagaoka Shiro , Irie Akinobu , Hamasaki Katsuyoshi , Yamashita Tsutomu
Published: July 2007

NbN nanobridge dc SQUIDs were fabricated by the field evaporation method and their noise characteristics were evaluated. The fabricated device has a magnetic flux‐voltage conversion efficiency Φ of about 2.5 mV/Φ0 and hence the device has a higher gain than that of the tunneling‐type device with a resistive shunt. The energy resolution is as small as 40 h. When the fabricated SQUID was installed in an FLL circuit and the dynamic range was measured, it is found that an output is proportional to the input for the input magnetic flux of ±32Φ0 without removing the lock. The magnetic flux resolution of the FLL circuit used is 9 × 10−10 Φ02/Hz in the white noise region (at 3 kHz). In the low‐frequency region less than 100 Hz, the 1/f noise described by 5.8 × 10−8 (1/f)Φ02/Hz was observed. This value of the magnetic flux resolution is large by one order of magnitude than that inherent to the device and the noise of the electronics is predominant.
Polarization‐independent guided‐wave optical hybrid coupler
Authors: Haga Hiroshi , Negami Takayuki , Yamamoto Sadahiko
Published: July 2007

A new guided‐wave hybrid coupler is proposed and its operating analysis is described. The device structure resembles that of a conventional directional coupler. It consists of a parallel portion in which two waveguides, with identical phase constants, are placed closely in parallel and of input and output sections, in which two waveguides separated sufficiently to allow input and output from other devices, adjoin the parallel portion. Although one of the input‐output sections is symmetric with the phase constants of the two waveguides equal, another has a nonsymmetric structure with different phase constants. The optical wave coupling in this non‐symmetric part plays an important role for the device operation.

In the analysis of operation, the coupling coefficient and difference of the phase constants between the waveguides are used as the waveguide parameters. The range of these parameters was obtained as necessary for stable operations in terms of difference in polarization and fabrication errors. It is shown that a rather large coupling coefficient and a large phase constant difference are needed in the case where the phase constant difference is constant. Hence, a new structure is proposed in which the phase constant difference increases gradually as the waveguide spacing is increased. This structure is analyzed. Unlike the conventional directional coupler, this structure has a large fabrication tolerance as regards the waveguide length in the parallel portion and the coupling coefficient and operation independent of the polarization can be obtained.
Improvement of power efficiency for the class‐BD amplifier with final bridge circuits
Authors: Mochimaru Masayoshi
Published: July 2007

The class‐D amplifier section used in a bridge‐type hybrid class‐BD (BHD) power amplifier is diminished to only one block by use of the full bridge configuration in the final stage. However, since the power loss in the full bridge is larger than that of the half‐bridge used in the original hybrid class‐BD (HD) amplifier, the BHD amplifier cannot overtake the HD amplifier in the power efficiency without selecting for a high load resistance.

This paper presents a new method for improving the power efficiency of the BHD amplifier by reduction of the power loss in the final bridge section. In the improved amplifier, the bias voltage applied to the bridge is minimized instantaneously corresponding to the load current. Moreover, the additional emitter resistor of the BJT for prevention of thermal run away is located in the base circuit. A high‐efficiency BHD amplifier with these modifications is developed which has an overall power efficiency of 92 percent at a large output (k = 0.92, output of 48 W) and of 33 percent at a small output (k = 0.1, output of 570 mW) for a load resistor of 8 ω and a distortion factor of less than 0.1 percent.
Study on discharge circuits for word‐lines in high‐speed bipolar rams
Authors: Yamaguchi Kunihiko , Homma Noriyuki , Sakurai Yoshiaki
Published: July 2007

To speed‐up the access of bipolar RAMs, the fall‐time of the word‐line drive voltage must be reduced by the discharge circuit. Various word‐line discharge circuits have been proposed for this purpose. This paper aims at the determination of the best discharge circuit for the future high‐speed, large‐capacity RAM. Four typical conventional kinds of discharge circuits plus one each newly proposed discharge circuit for small and large capacities are applied to the same memory cell array, and the performances are compared by circuit simulation with the same load condition and the same device.

As a result, when the degree of integration is not very high and the voltage drop in the word‐line can be ignored, the conventional delayed‐type discharge circuit is the best. When the integration is high and the voltage‐drop in the word‐line cannot be ignored, the newly proposed discharge circuit flowing the discharge current also from the upper word‐line is shown to be the best. Thus, it is concluded that the newly proposed discharge circuit is well‐suited to the future high‐speed, large‐capacity RAMs. The performance of the typical delayed‐type discharge circuit is actually measured for 4‐kbit RAM; and it is verified that the fall‐time of the word‐line drive voltage is reduced, as in the result of simulation. This paper presents a discussion concerning primarily the comparison of performances among the newly proposed and conventional discharge circuits.
Stress analysis of a metal cap with sapphire windows for hybrid ICs
Authors: Fukuoka Yoshitaka , Nishimura Takuya , Terao Takahiro
Published: July 2007

To hermetically seal a hybrid IC with several EPROM IC ships, sapphire windows are brazed to a metal cap. Since it was necessary to investigate the pressure resistance of the sapphire windows, stress analysis was performed using the finite element method. In stress analysis, we consider the thermal stress generated in brazing the sapphire window on the metal cap, the forced stress generated in the hermetic seal process of the hybrid IC and the pressured stress generated in the hybrid IC. The allowable stress in sapphire was measured by the bending test with two‐point support to obtain the stress limit of sapphire. The theoretical and experimental results were compared to confirm the validity of the analytical model.

The analytical method developed in this study will be helpful to achieve high reliability in a hybrid IC with sapphire windows.
Some interesting transmission characters of nonradiative dielectric waveguides using high‐permittivity material
Authors: Shinohara Soubee , Yoneyama Tsukasa
Published: July 2007

The nonradiative dielectric waveguide (NRD‐guide) is a dielectric waveguide which normally is composed of low‐permittivity dielectric materials; but, if high‐permittivity materials are used, then the circuit size may be reduced. However, when high‐permittivity materials are used, then single‐mode transmission becomes impossible and some unpredictable phenomena are observed which have never been observed in a low‐permittivity waveguide.

In this paper, transmission characteristics of the high‐permittivity nonradiative dielectric waveguide are studied theoretically as well as experimentally. Assuming that the presence of small air gaps between the dielectric strip and metal plates of the NRD‐guide, which cannot be avoided in practice, is the origin of these phenomena, the analysis has been performed which shows that a serious effect occurs even for extremely small gaps and the bandwidth of single‐mode transmission becomes very small. Ultimately, this makes the single‐mode transmission impossible. The electromagnetic field distribution in the NRD‐guide is also calculated and the curious phenomena are interpreted physically. Moreover, a trapped insular NRD‐guide is proposed which permits single‐mode transmission even if high‐permittivity material is used. An experimental confirmation is made of the usefulness of this new type of NRD‐guide.
Some characteristics of Pd electrical contacts mounted on relays that make and break a dc 30‐v, 10‐a resistive circuit
Authors: Kubono Takayoshi
Published: July 2007

A description of some of the measured characteristics of palladium switching contacts mounted on miniature relays is presented.

For 100,000 switching operations of Pd contacts in the dc 30‐V, 10‐A resistive circuit, we measure the duration of each closing and opening are at each switching, the contact resistance at each closure, the temperature of supporting arm nearby the stationary contact, the number of bouncing at each closure, and the number of switching actions with normal switching functions. Then we compare the data with those data on Ag, AgCdO12 wt% and AgSnO29.3 wt% contacts.

On contacts with duty‐making current, closing‐arc duration is very short and the amount of metal transfer is very small. On contacts with duty‐breaking current and those with both making and breaking duty, the large amounts of metal transfer that result will create a large pip and a deep crater on each contact pair.

These large pips, deep craters, and the palladium oxide of true contact area influenced greatly each characteristic. Therefore, an obvious difference did not appear between each characteristic in nonpunched contacts and those in punched contacts.

After several thousand switching operations, the real contact area consists of a large pip and a crater with a whitish surface; this contact area is made by metal transfer and is made of palladium oxide. It is discussed here that these large oxidized palladium pips and craters influence greatly arc duration, contact resistance, contact sticking, and shortening of the closing‐arc duration simultaneously with an increase in the number of switching operations.
Fabrication of sin thin films by rf biased microwave plasma CVD
Authors: Itoh Naomi , Kato Kiyotaka , Kato Isamu
Published: July 2007

The purpose of this study is to clarify the effect of ion bombardment during the deposition of silicon nitride film. Since silicon nitride is an insulator, ion bombardment was controlled by RF bias to the substrate. When the effective value of the RF voltage was increased from 0 to 120 V, the self‐bias, which is an indicator of the acceleration voltage of ions is impinging on the film, monotonically changed from 0 to −75 V.

Therefore, when RF voltage is increased, the ion bombardment increased, hydrogen content in the film decreased, the content of nitrogen and silicon in the film increased, and the film density increased. This phenomenon is caused by the acceleration of surface reaction due to the thermal effect on the film surface by the increase of ion bombardment. The Si/N ratio was constant regardless of the RF voltage.
Three‐dimensional electromagnetic analysis of rectangular waveguide containing high‐permittivity anisotropic dielectric
Authors: Ko Youngho , Yoshida Norinobu , Fukai Ichiro
Published: July 2007

Various waveguides made of different materials with complex configurations have been reported for use at the millimeter‐wave frequencies to optical wavelength. In general, it is difficult to analyze vectorially the characteristics of the waveguide with a three‐dimensional shape.

In this paper, the spatial network method using all of the electromagnetic field components is employed as a vector analysis method to analyze a rectangular waveguide loaded with an anisotropic material with an extremely high relative permittivity. As the anisotropic material, the iron‐doped rutile used in a traveling‐wave maser is assumed.

First, the propagation constant for the basic mode of the rectangular waveguide loaded completely with an anisotropic material is obtained. Next, the change of the propagation characteristics for the symmetric and non‐symmetric cases is studied for a rectangular waveguide partially loaded with an anisotropic material. The electromagnetic field distributions are presented for the case where the relative permittivity tensor of the anisotropic material has only the diagonal terms and where off‐diagonal terms exist. By means of the time domain analysis, the wave propagation in an anisotropic material can be found successively so that the effects of the boundary shape and the medium condition can be known directly.
Achromatic liquid crystal display using homogeneously oriented nematics with a compensation layer
Authors: Takahashi Taiju , Saito Susumu
Published: July 2007

This paper describes a homogeneously oriented LCD with a homogeneously oriented Np driving layer and a homogeneously oriented Np compensator and its characteristic. In general, in such an LCD, the V‐T characteristic improves as 〈Δn〉10d1 becomes larger. When the elastic constant ratio K33/k11 is small and the dielectric constant ratio is close to unity in the Np material, the V‐T characteristic remains sharp even if 〈Δn〉10d1 is small. Considering both high time‐division driving and low‐voltage driving, vp and n should be chosen so that 〈Δn〉= 〈Δn〉p = 〈Δn〉n does not deteriorate. Using ZLI‐2842 (manufactured by Merck & Co., Inc.), 〈Δn〉 of 7.5 percent was obtained when 〈Δn〉10d1 = 0.76 μm, where the achromaticity was comparable with that in the VAN type. As 〈Δn〉10d1 increased, the viewing angle characteristic became worse. In a cell with 〈Δn〉10d1 suitable for high time‐division driving at a duty cycle lower than 1/200, the viewing characteristic was worse than those in the VAN CSH types. However, in a homogeneously oriented Np LCD, the instability caused by the dynamic scattering effect which is common in the VAN type does not occur.
Analysis of short‐channel effect in thin‐film SOI MOS transistor
Authors: Nakamura Kaori , Okura Yasuyuki , Takeda Eiji , Izawa Ryuiti
Published: July 2007

The short‐channel effect in thin‐film SOI MOS‐FETs was analyzed by two‐dimensional, two‐carrier simulation. In thin‐film SOI MOSFETs, the channel length dependence of the threshold voltage is influenced strongly by the avalanche effect caused by impact ionization. It was found that the short‐channel effect is enhanced by the avalanche effect.

The holes generated by impact ionization raises the substrate potential, causing a decrease in the potential barrier between the source and substrate. In bulk MOSFETs, the potential barrier is not affected by the holes generated by the avalanche effect because the holes flow into the substrate electrode. However, in thin‐film SOI MOSFETs, the potential distribution near the source is influenced strongly by the holes because the holes flow into the source. The holes generated by the avalanche effect degrade the punch‐through breakdown voltage. The punch‐through breakdown voltage is highest when the SOI layer has a certain thickness. When the layer thickness is lower than a certain thickness, the punch‐through breakdown voltage decreases. The punch‐through breakdown voltage is lowest when the underlying oxide film is a certain thickness.
A bitmap memory bank which allows block accesses
Authors: Takakubo Hajime , Pham Cong‐Kha , Shono Katsufusa
Published: July 2007

Along with the development of high‐density memory devices (Mbit DRAM), there have been many studies on how to manage two‐dimensional binary data by employing a bitmap method. A special purpose, memory bank for systematically managing bitmap data has been produced. It can be used for various purposes, not only for bitmap CAD but for enumerating binary or gray images expanded on a bitmap editor. In order to transfer bitmap data on the scale of a few Mbits within a practical time, the memory bank executes an access of bitblt method using special purpose hardware for addressing, memory accessing, and bitwise operations. In this study the hardware consists of TTL, PAL, RAM, a custom LSI DRAM controller chip and a custom LSI bit operation chip. The system has a programmable sequencer which makes access from MS‐DOS possible. The memory access rate is 20 Mpixel/s in the case that extended regions are transferred while refreshed and logical operations are being performed.
Quasi‐E junction in a planar circuit
Authors: Takashima Mitsugu , Iga Hiroaki
Published: July 2007

In the E‐junction, when the phase shifts from the E‐arm to two straight arms are in‐phase and out‐of‐phase, respectively, the phase shifts in the opposite directions are also in‐phase and out‐of‐phase. On the other hand, in the quasi‐E junction which is a T‐shaped three‐way junction, when the phase shifts from the vertical arm to the two straight arms are in‐phase and out‐of‐phase, the phase shifts in the opposite direction are out‐of‐phase and in‐phase, respectively.

In this paper, the quasi‐E junction characteristics are studied and two circuit configurations and their elements are derived. Next, the relationship between the quasi‐E junction and the E junction is studied. The result found is the symmetry. Also, the two circuit configurations are actually circuit systems. One of them is made of two gyrators (a nonreciprocal circuit in which the phase shift from the left to the right is −π/2 while the one in the opposite direction is π/2) and an H‐plane T junction in which the phase shifts between the vertical arm and each straight arm is −π/2 if the phase shift between the ends of the straight arms is π. From the measured results of the circuit system designed and fabricated, the operating principle of the quasi‐E junction is confirmed.

The circuit configuration in this paper contains active devices since active gyrators are used. However, due to the fact that it is a planar circuit, the technology is important for MIC.
An analog neurochip and its applications to multilayered artificial neural networks
Authors: Masumoto Daiki , Ichiki Hiroki , Yoshizawa Hideki , Kato Hideki , Asakawa Kazuo
Published: July 2007

A multipurpose neurochip (analog neuroprocessor) has been developed that incorporates neural networks into equipment. This paper describes this analog neurochip and the multilayered artificial neural networks that run on it. This chip was built using 2‐μm Bi‐CMOS technology. Input/output signals are analog and weights are digital. An analog time‐sharing bus is used for input and output; analog data can be sampled at intervals of 13 μ. An example of the exclusive‐OR problem has been included. Construction of a three‐layered network using the chips required development of a system that consists of the following:

chip

memory to store weights

board on which chips, memories, and control circuit are mounted

software simulator dedicated to error backprop‐agation learning

This system performs parallel processing in each network layer and executes pipeline processing between the layers. It has a processing speed of up to 0.6 million interconnections per second (MIPS). The current chip has some problems, including dispersion of device characteristics, loss of significant digits of weight, and digit overflow. Some countermeasures for these problems also are examined.
Optical phase‐locked loop for suppression of external disturbances in optical fiber sensors
Authors: Hirose Yasuo , Tsuzuki Yasuo , Ando Haruo
Published: July 2007

Very high sensitivities can easily be achieved in optical fiber interference‐type sensors which are also sensitive to such external disturbances as low‐frequency phase changes of interference‐light, oscillations getting into the optical system in the form of frequency fluctuations, etc. To realize stable measurements, it is very important to suppress these effects.

This paper investigates the second‐order optical phase‐locked loop (OPLL) developed to suppress such fluctuations due to external disturbances and treats an optical vibration sensor as an example. By introducing small‐amplitude phase variations into the interfering lights, a new detection method is adopted to investigate the effects of external disturbances. It can suitably be applied to fiber‐transmission type sensors to which it was difficult to apply the previous differential detection methods for the purpose of compensating external disturbances. The OPLL remains locked in at about 50‐Hz frequency pulling range and can suppress frequency and phase variations caused by external disturbances having frequency components of at most 10 Hz.
Analysis of crosstalk between parallel microstrips using finite‐difference time‐domain method
Authors: Maeda Shuji , Kashiwa Tatsuya , Fukai Ichiro
Published: July 2007

Recently, malfunctions by crosstalk between signal lines have become a problem in an electronic circuit which has been more densely organized and handles signals at higher frequencies. To prevent malfunctions due to these noises, it is important to find the relationship of the crosstalk with the materials and structures of the circuit board. Especially, as the density is increased, the use of multilayered configuration is increased so that the understanding of the crosstalk between interconnects arranged in a three‐dimensional fashion is increasingly more important.

Usually, the analysis of crosstalk has been carried out by means of the equivalent circuit analysis. It is not easy to adjust the number of discretizations and the analysis between the three‐dimensional (3‐D) interconnects.

In reference to the foregoing, this paper describes a crosstalk analysis between parallel microstrips by means of the finite‐difference time‐domain (FD‐TD) method which, among the 3‐D electromagnetic field analysis methods, requires small memory and computational time. Good agreement is confirmed between the thoretical and experimental results on the crosstalk waveforms and the crosstalk coefficient. Hence, the effectiveness of the FD‐TD method for the crosstalk analysis has been confirmed. It is believed that the FD‐TD method is extremely effective for analysis in the circuit design.
Study of the thermal stability of AI12 W/W/Si contact structure by AES analysis
Authors: Sasaki Katsutaka , Noya Atsushi , Takeyama Mayumi , Bando Masato
Published: July 2007

The thermal stability of the contact system of the AI12W intermetallic compound film with Si was investigated by AES analysis. The diffusion of Si into the film is observed in the AI12W/Si direct contact system at temperatures above 250°C, while the Si diffusion in the AI12W/W/Si system can be completely blocked up to 550°C, but the barrier properties of the W layer interposed are thickness‐dependent; W layer must be thick enough to separate the AI atoms in AI12W layer from the Si substrate. It is shown that the use of AI12W films combined with W in contact systems is a useful metallization technology for Si‐LSI.
A 40‐Msps 10‐bit video BiCMOS analog‐to‐digital converter
Authors: Sugimoto Yasuhiro , Tsugaru Kazunori
Published: July 2007

A 40‐Msps 10‐bit video A/D converter LSI has been developed. A 0.8‐μm BiCMOS technology is applied. The two‐step parallel type conversion scheme is adopted, using the MOS analog switch and bipolar comparator. A redundant structure is employed using 5 bits for the coarse stage and 5.5 bits for the fine stage. Three points of voltages in the coarse ladder circuit are transferred to the fine ladder resistor circuit and are used as the upper‐end, middle‐point and lower‐end voltages.

Wire connection configuration for the fine ladder resistors is redesigned so that the error is reduced and the speed is improved. A high‐speed circuit with a preamplifier is used in the fine comparator. Protection functions for the overflow and underflow are also provided. With this design, the S/N ratio of 60 dB is realized, for the clock frequency of 40 MHz and the full‐scale 50‐kHz input. The designed LSI operates with the 5‐V single supply. Power consumption is 700 mW, the number of elements is 7000, and the chip size is 4.1 × 4.8 mm2. The following performance is obtained by overall evaluation of the printed board containing the S&H IC and DAC. The D.G. and D.P. for 40‐MHz clock are 1 percent and 1 deg, respectively. The S/N ratio is 52 dB for 10 MHz full‐scale input and 48 dB for 20‐MHz full‐scale input. A future problem involves the on‐chip implementation of the S&H circuit.
Pulse response of high Tc superconductive transmission line
Authors: Furusawa Satoshi , Morisue Michitada , Asahina Jyoji
Published: July 2007

This paper studies the transmission characteristics of the microstrip line consisting of a YBCO high temperature superconducting material and investigates the effect of attenuation and distortion of the pulse propagating along such a transmission line. The effectiveness of high temperature superconducting material for interchip and intrachip interconnections is described. Presently, the high temperature superconducting thin film devices are often made on an MgO substrate that has rather high permittivity and a high dielectric loss. Calculation of the characteristics of the transmission line based on the two fluid model is used to demonstrate that the effect of the dielectric loss of the substrate becomes significant at the frequency range below 20 GHz; further, the attenuation constant increases by two orders of magnitude in comparison to the case without the loss caused by the substrate. However, the attenuation constant is smaller than that of the A1 interconnect at 77 K and the phase constant is almost constant independent of frequency so that this transmission line has excellent properties.

The distorted wave is derived by simulation when a pulse is applied to this transmission line. It is demonstrated that the line of an MgO substrate at 77 K is superior as a transmission line. On the other hand, a YBCO microstrip line was fabricated on an MgO substrate. The attenuation and phase constants were measured and compared with the theoretical values.
An optoelectronic device using Au‐diffused Pb2CrO5 thin films
Authors: Toda Kohji , Yoshida Shinzo
Published: July 2007

To form a thin‐film line‐image sensor with high density and a high‐speed response, an optoelectronic device was fabricated using a gold‐diffused Pb2CrO5 thin film; its basic characteristics were evaluated as well. A Pb2CrO5 film was deposited using the electron beam evaporation method; this was followed by the deposition of an Au film. The Au was then thermally diffused. As a result, the photoresponse was increased by 150 times, without degrading the spectral response characteristic and the photocurrent/dark current ratio.

After Au diffusion, the bias voltage dependence of the photocurrent changed from a parabolic to a linear relationship and the γ coefficient changed from 0.5 to 0.7. In addition, the photoresponse and the transient characteristic in the pulse voltage operation of the Pb2CrO5 thin‐film sensor array were improved. It was confirmed experimentally that the resulting device is suitable for high‐speed and high‐density read‐out.
LSI‐oriented scanning systems using tree structures
Authors: Kondo Toshio
Published: July 2007

Two types of scanning systems using N‐ary tree structures are proposed for high‐speed intelligent processing in an SIMD parallel processor. The scanning systems are constructed by connecting operating elements to each other with hierarchical bypasses or hierarchical and selective propagation paths. After evaluating their operating times, the amount of hardware, and LSI implementation, the following conclusions were reached: (1) the number of serially operating elements in the propagation path is only O(N logN M); (2) enlarging the N‐value decreases the amount of hardware; (3) the selective‐type scanning system is twice as fast as the bypass‐type system although both require almost the same amount of hardware; and (4) a 42‐ary tree structure leads to a simple and dense chip layout.
Soliton‐type femtosecond pulse lasers
Authors: Ishida Yuzo , Nakano Hidetoshi
Published: July 2007

The propagation of optical pulses in optical fibers through an optical soliton has been studied widely. The results of the studies have contributed not only to the development of ultrafast optical communication but also to the creation of a soliton laser designed for generating ultrashort optical pulses. The soliton concept is applied successfully to the generation mechanism of ultrashort optical pulses in a laser cavity. This paper will describe the generation of femtosecond optical pulses in soliton lasers and in solitons in the laser cavity.
Optical sheet memory system
Authors: Ohyama Shinji , Nagae Yoshiharu , Takasaka Masahiro
Published: July 2007

This paper proposes a system for information storage and delivery. It is based on the new concept where the information corresponding to 10 still pictures and approximately 3 min of sound are encoded digitally and printed on a postcard as a dot pattern to be read and restored. The system is called an optical postcard system.

In this study, after the basic technologies for the realization of this system are investigated, the printed optical postcard and the reproducing system are constructed experimentally. As a result of there production experiment, the information recorded on the postcard is read and the original picture and sound signal are played back. This indicates that the information can be delivered by optical postcard. The proposed idea of an information storage/delivery system can be applied not only to postcard‐sized sheet, but also to sheets of various sizes. Also, there can be various applications which differ from
the use of the traditional information media, e.g., the the use of the traditional information media, e.g., the zine.
Generation of ultrafast laser pulses by electrooptic modulation
Authors: Kobayashi Tetsuro
Published: July 2007

The passive mode locking traditionally used frequently for generation of ultrafast optical pulses has a problem in generality and controllability although the method can generate short pulses. On the other hand, it is considered that the method based on electrooptic modulation cannot reduce the pulsewidth and the speed is slow even though the controllability is superior.

This paper describes the research on the forced mode‐locking method for possible ultrashort and ultrafast properties and the external direct modulation pulse generation method, even though the highly controllable electrooptic modulation is used. First, the forced mode‐locking method is described in which the locking modulator (mode locker) with a pulse‐like transparency in itself and a deflector and a composite resonator are used.

Next, a method is described in which short pulses on the order of subpicoseconds can be generated regardless of the laser bandwidth by means of the pulse‐generating modulator outside the laser cavity. (An example is a modified Fabry‐Perot modulator.) Further, an optical pulse synthesizer with a possibility of generating subpico‐second to several tens of femtosecond pulses is described in which the narrowband large signal electrooptic modulator and a deflector are used for generating optical sidebands with a wide optical bandwidth and they are combined for generation of arbitrary‐shaped optical pulse after the phase and amplitude are controlled. The concept is compared with the experiments. Some methods are still under development.
Fast recovery of excitonic absorption bleaching in tunneling Bi‐quantum well
Authors: Tackeuchi Atsushi , Inata Tsuguo , Muto Shunichi , Sugiyama Yoshihiro , Fujii Toshio
Published: July 2007

Excitons in a quantum well of a semiconductor exhibit large optical nonlinearity. Therefore, a quantum well of a semiconductor is regarded as a key to realizing a device which can control light using light. However, the lifetime of excitons, which are generated optically, is several nanoseconds to several tens nanoseconds. Therefore, the nonlinear optical effect including absorption saturation continues for the lifetime of the excitons.

To shorten the lifetime of the excitons without disturbing the optical nonlinearity, a new superlattice structure is proposed called the “tunneling bi‐quantum well.” This structure uses the tunneling effect and measures the absorption recovery time. As a result, it was found that in a tunneling bi‐quantum well in a GaAs/AlGaAs system with a barrier width of 1.7 nm, the absorption recovery time was as short as 1 ps.
Equivalent characteristic impedance formula of waveguide and its applications
Authors: Ishihara Fujio , Iiguchi Shinichi
Published: July 2007

The equation widely known as the characteristic impedance of the waveguide is defined from the voltage in the cross section, wall current along the axial direction and Poynting vector. For the rectangular waveguide, the impedance has a form proportional to (b/a)λ. However, it is not possible to derive a correct reflection coefficient with this form of characteristic impedance. It has been predicted empirically by the present authors and others that the characteristic impedance connected directly to the reflection coefficient has a form proportional to bλg. However, investigation of the theoretical foundation has not been carried out clearly.

In this paper, based on the fundamental differential equation describing the characteristics of the nonuniform waveguide, a transmission line equivalent to the waveguide is derived. By means of this transmission line, the forementioned characteristic impedance is proven to be theoretically correct. Here, this quantity is called the equivalent characteristic impedance.

Based on this result, it is proved that there are several different procedures for the analysis of the characteristics of the tapered waveguide and that they all arrive at the same results. The theoretical results are verified by three different experiments. In addition, the applications of this equivalent characteristic impedance are described for the design of the connecting tapered waveguide and the quarterwave transformer.
Polarization control of Q‐switch solid‐state lasers with intracavity SHG crystals
Authors: Taira Takunori , Sasaki Takao , Kobayashi Takao
Published: July 2007

Wavelength conversion of a laser beam by nonlinear optics has been widely developed for practical applications because optical output with different wavelengths can be obtained efficiently without disturbing the coherence of the fundamental wave. Especially, in the intracavity second harmonic generation (SHG) technique which utilizes a nonlinear optical crystal in the laser cavity, the efficiency and output are high because an intense fundamental wave is used; KTP (KTiOPO4) is an excellent crystal with a high nonlinear optical coefficient. However, when it is placed inside a cavity, the polarization characteristic of the fundamental wave is disturbed because of the birefringence of the crystal. As a result, during Q‐switching, the loss of the fundamental wave in the polarizer increases and the oscillation threshold increases. Therefore, polarization control of the fundamental wave has been carried out by using a γ/4 plate.

In this paper, the optical properties of a KTP crystal are analyzed using John's matrix and it is found that polarization control of the fundamental wave could be achieved with maintaining phase matching. Next, by analyzing the operation of the Q‐switch laser by the intracavity SHG‐method, optimization was carried out. As a result, low‐loss polarization control was realized without using a wavelength plate inside the cavity. Then a highly efficient SHG characteristic was realized, wherein the effective efficiency was 84 percent at repetition frequency of 1 kHz and the maximum output was 3.2 W at repetition frequency of 5 kHz.
Laminated polarizer with granular metallic films for short wavelength region (∼0.85 μm)
Authors: Ma Deshan , Tsuchida Kanji , Kawakami Shojiro , Kataoka Haruki
Published: July 2007

A laminated polarizer (LAMIPOL) is smaller in size and has a higher extinction ratio and lower insertion loss than the conventional polarizer. Therefore, it is suitable for optical integration. However, when a LAMIPOL with a conventional continuous metallic film is used in a short wavelength region, the property is not sufficiently good.

On the other hand, we fabricated a Cu/SiO2 LAMIPOL and achieved an extinction ratio of 46 dB and insertion loss of 0.3 dB, which are better than theoretical values for the device with a continuous film. After detailed investigation of this particular device, it was found that the metal film had granular structure.

To investigate the superior characteristic of a LAMIPOL with granular metallic films, a simple model for a granular Cu film was proposed, and the film parameters were estimated using the wavelength dependence of the optical transmittance and reflectance. Using these parameters, the wavelength dependencies of the attenuation constants of LAMIPOL for TE and TM waves were calculated. The agreement between the experimental and calculated results were excellent.
Nonlinear interaction between optical solitons and maximum transmission capacity
Authors: Shimizu Katsuhiro , Fujii Yoichi
Published: July 2007

The very short optical soliton pulse transmission for the very high‐speed communication system is limited by the dispersion of the fiber. The problems due to the neighboring solitons, especially in the wavelength‐multiplex soliton transmission, is analyzed theoretically. As a numerical example, the soliton pulse of 2 ps pulsewidth with the preemphasis factor 1.4 can transmit 150 Gbit/s pulses for 12 km and by the wavelength‐division multiplex system, the 20 channel pulses with the wavelength spacing 1 nm and of 5 ps pulsewidth can transmit the pulses by 400 Gbit/s.
Millimeter‐wave junction circuits using nonradiative dielectric waveguide
Authors: Kuroki Futoshi , Yoneyama Tsukasa
Published: July 2007

The nonradiative dielectric waveguide (NRD guide) is suitable for constructing millimeter‐wave circuits of complicated structure because of nonexistence of radiating wave at the bend and discontinuity based on the non‐radiative nature, the construction technique of the T‐junctions, the cascaded multiport junctions in NRD guide, and their performances at 50 GHz are described in this paper.

First, a new T‐junction based on the mode transformation between the two types of nonradiative modes in the NRD guide is proposed and its operation is confirmed experimentally. Next, using this T‐junction, a three‐port and a five‐port junction have been fabricated and tested. Reasonable output levels of ‐3 dB and ‐6 dB in average for the three‐port and five‐port junctions were obtained, respectively, over a bandwidth of about 2 GHz with the center frequency at 50 GHz. From this fact, it is evident that the radiation loss which cannot be suppressed in conventional dielectric waveguide junctions can be completely eliminated in the NRD‐guide junctions.

The output ports of these junctions can be increased by stacking several T‐junctions. These junctions can be applied for feed network of millimeter‐wave planar antenna in the future.
Direct Overwrite Characteristics of InSbTe Phase‐Change Optical Disks and the Mechanism
Authors: Maeda Yoshihito , Andoh Hisashi , Nagai Masaichi , Ikuta Isao , Katoh Yoshimi , Tuboi Nobuyoshi , Minemura Hiroyuki , Satoh Yoshio , Ishigaki Masaji
Published: July 2007

This paper examines the direct overwrite characteristics of a 5.25‐inch diameter disk fabricated with an InSbTe ternary‐alloy recording film. This recording film has a novel optical property, namely that the reflectivity is larger in the amorphous (recorded) state than in the crystalline (erased) state. To improve the erasability in direct overwrite, melt‐erasing process was attempted and carried out above the melting point. A high erasability of more than 40 dB and a high carrier‐to‐noise ratio (C/N) of more than 50 dB were realized at the rotating speed of 1800 rpm. A simple model explaining the contribution of the thermal conditions of the melt erasing to the high erasability is proposed.
Tunable waveguide CO2 laser making use of three‐mirror‐type internal modulation method
Authors: Matsushima Tomoshi , Maeda Naoki , Nakao Masatoshi , Kobayashi Tetsuro , Sueta Tadasi
Published: July 2007

A novel frequency‐tunable CO2 laser system using an internal modulator is proposed. In the proposed scheme, a tunable filter is used as the output laser mirror. One of the sideband components produced by the modulator is taken out efficiently by the filter as a frequency‐shifted output.

From the analysis of internal modulation, the relation between frequency‐shifted output power and modulation index is obtained using the single‐pass laser gain as a parameter. It is shown that a laser with higher gain is favorable for this system. The effect of the modulator location in the laser cavity also is discussed.

An experimental system using a CdTe internal modulator and a Fabry‐Perot interferometer was constructed. By the modulation experiment at the VHF band, the output power of 1.5 W was obtained for the frequency shift of ±150 MHz. The output power for ±1.45 GHz shift (UHF band) was 70 mW.

Finally, possible output power for SHF modulation is estimated using the published data for a traveling‐wave modulator. Calculation shows that several hundred milliwatts of frequency‐shifted power would be obtainable by the proposed method.
Considerations of ultrahigh‐speed, low‐power active pull‐down NTL logic circuits
Authors: Usami Mitsuo , Nakamura Tohru , Shiozawa Noboru , Tanabe Masamichi , Mandai Takahiro
Published: July 2007

Low‐power logic circuits are necessary in order to realize high‐integration, ultrahigh‐speed logic LSIs. For this purpose, a new circuit is proposed which adds an active pull‐down circuit to an NTL circuit with emitter follower which is a logic circuit with small logic swing of 500 mV. Compared to the conventional ECL circuit, this circuit achieves 2.75 times higher speed under 1 mW/gate power and an average wire capacitance of 0.57 pF per gate.

As a result of fabricating this active pull‐down NTL logic circuit by 0.5 μm SICOS self‐aligned transistor with U‐groove, a minimum delay time of 25.3 ps, and the load drive capability of 50 ps/pF have been realized.

Furthermore, this circuit can achieve even lower power with high speed by adding a pMOS transistor to the collector of input transistor. The simulation has shown that the circuit is four times faster compared to the conventional NTL circuit with an emitter follower with the same power consumption of 0.3 mW/gate and the load capacitance of 1 pF if a pMOS drain current of around 1 mA can be realized with conditionsVds, = ‐0.5 V andVgs= ‐1.3 V.
Geometrical law of total reflection for wave‐normal rays on the discontinuous interfaces in inhomogeneous media
Authors: Hashimoto Masahiro
Published: July 2007

When the wave‐normal ray associated with a spherical wave is incident upon an interface between two homogeneous media and undergoes a total reflection, the angle of reflection differs slightly from the angle of incidence. The position of the image source, which so far has been known to be located at the position geometrically symmetrical to the real source, also shifts.

This paper shows that similar phenomena occur for the case when the media are inhomogeneous. Moreover, it also shows that the expressions obtained for the location of the image source and its phase are completely coincident with those obtained earlier in homogeneous media.
Control of GaInAs/InP layer thickness for surface‐emitting lasers by chemical beam epitaxy
Authors: Uchida Takashi , Uchida Toshikazu , Koyama Fumio , Iga Kenichi
Published: July 2007

To grow a highly reflective semiconductor multilayer mirror and to grow a reproducible composition of GaInAsP/InP for surface‐emitting lasers, a high growth rate (a few μm/h) with a good thickness controllability is required. The authors have investigated the controllability of GaInAs/InP growth of chemical beam epitaxy (CBE). The maximum growth rate of 2.6 μm (InP) and 6.0 μm/h (GaInAs) was obtained without sacrificing surface morphology. With the growth rate being kept reasonably high, a good controllability of layer thickness was obtained and confirmed by growing a 6‐Å quantum well. The thickness error for InP and GaInAs was 1.5 and 2.0 percent, respectively.
Photonic ATM switch using vertical‐to‐surface transmission electro‐photonic devices (VSTEPs)
Authors: Nishio Makoto , Takagi Kazuo , Suzuki Shuji , Kaede Kazuhisa , Ogura Ichiro , Numai Takahiro , Kasahara Kenichi
Published: July 2007

This paper proposes a new architecture of photonic ATM switch for the purpose of eventually moving beyond the terabits‐per‐second (Tbps) level throughout ATM operation. The proposed architecture is based on vertical‐to‐surface transmission electro‐photonic devices (VSTEPs) which can be used both as an optical buffer memory and as an optical self‐routing circuit. Since VSTEP is an integrated two‐dimensional array, the VSTEP‐based optical buffer memory using massively parallel optical interconnections based on the free‐space optical beam propagation is an effective solution to achieve ultrahigh throughput in the buffer. The optical cell signal speed in the proposed optical buffer memory can reach about 10 Gbps. By using the VSTEP function as the optical header‐driven gates in a two‐dimensional array, the high‐speed and large‐capacity optical self‐routing circuit can be fabricated without being limited by the electric control circuit operation.

In the proposed optical self‐routing circuit, priority control to prevent collision among cell signals at the output port in the case of cell signal contention can easily be achieved. The numbers of possible input and output ports in the self‐routing circuit are estimated to be around 100. An optical header is inserted at the front of the ATM cell signal for processing at the self‐routing circuit. To reduce the overhead of the optical header, a wavelength‐division technique also is proposed for the self‐routing circuit. Finally, experiments on operations of both the buffer memory and the self‐routing circuit with priority control for 1.6‐Gbps optical cells are carried out successfully.