785 nm (AlGaAs) laser diode (LD) with a window-mirror structure is demonstrated to be a potential candidate as a highly reliable light source of CD-R. The intermixing of a multi-quantum well structure by silicon implantation is used to form the window-mirror structure. Carbon is adopted as an acceptor because of its low thermal diffusion constant in crystals. As a result, the window-mirror-structure 785 nm AlGaAs LDs with ordinary far field patterns suitable for the actual CD-R drives have shown stable single lateral mode operation up to 250 mW. A mirror degradation level is significantly increased by the window-mirror structure. The pulsed operation current at 160 mW, 70 of the carbon doped LD is reduced by about 15% from that of zinc doped one. Highly reliable 160 mW pulsed operation is also realized at 70. This LD believed to be suited for the next generation high-speed (16-24x) CD-R drives necessitating 160 mW class LD.

A new approach for extracting significant characteristic within speech signal for distinct speaker is presented. Based on the multiresolution property of wavelet transform, quadrature mirror filters (QMFs) derived by Daubechies is used to decompose the input signal into varied frequency channels. Owning to the uncorrelation property of each resolution derived from QMFs, Linear Predict Coding Cepstrum (LPCC) of lower frequency region and entropy information of higher frequency region for each decomposition process are calculated as the speech feature vectors. In addition, a hard thresholding technique for lower resolution in each decomposition process is also used to remove the effect of noise interference. The experimental result shows that by using this mechanism, not only effectively reduce the effect of noise inference but improve the recognition rate. The proposed feature extraction algorithm is evaluated on MAT telephone speech database for Text-Independent speaker identification using vector quantization (VQ). Some popular existing methods are also evaluated for comparison in this paper. Experimental results show that the performance of the proposed method is more effective and robust than that of the other existing methods. For 80 speakers and 2 seconds utterance, the identification rate is 98.52%. In addition, the performance of our method is very satisfactory even at low SNR.

We propose a compact multi-channel 90 optical deflection device for short-distance optical interconnection. The device consists of stacked bent multimode optical waveguides having reflecting mirrors with bending angles of 90. The structure of the bent multimode optical waveguide with a bending angle of 90 was designed by ray-tracing simulations. The simulated insertion loss for each channel of the device was 0.5 dB. We also propose a simple fabrication process using a pair of multi-channel linear optical waveguides with symmetrical 45 mirrors. An 8-channel 90 optical deflection device was fabricated using polymer materials and basic operation was confirmed. Our device has good potential for use as a high-density optical interconnection device.

This study presents two new bit-parallel cellular multipliers based on an irreducible all one polynomial (AOP) over the finite field GF(2m). Using the property of the AOP, this work also presents an efficient algorithm of inner-product multiplication for computing AB2 multiplications is proposed, with a structure that can simplify the time and space complexity for hardware implementations. The first structure employs the new inner-product multiplication algorithm to construct the bit-parallel cellular architecture. The designed multiplier only requires the computational delays of (m+1)(TAND+TXOR). The second proposed structure is a modification of the first structure, and it requires (m+2) TXOR delays. Moreover, the proposed multipliers can perform A2iB2j computations by shuffling the coefficients to make i and j integers. For the computing multiplication in GF(2m), the novel multipliers turn out to be efficient as they simplify architecture and accelerate computation. The two novel architectures are highly regular, simpler, and have shorter computation delays than the conventional cellular multipliers.

For the realization of low-voltage full-color FEDs, requirements for phosphor for the FED are proposed. Especially, the influence of released gases or substances from phosphors on the field emission within the FED was made clear. It was clarified that the analysis of F-N plots of the V-I curve of field emission characteristics was helpful to know the interaction of field emission and phosphors. In the experiment, we first obtained the depth from the phosphor surface of the low voltage electron excitation in case of ZnGa2O4, where the region available for cathodoluminescence at the anode voltage of 400 V is about 63 nm deep from the surface. The characteristic of the 12.4 cm-320(trio)240 pixels low-voltage full-color FED is reported. The luminance of 154 cd/m2 was attained at the anode voltage of 400 V and the duty factor of 1/241. Supported by the high potential of the FED as a flat panel, each problem shall be steadily solved to secure the firm stand as a new full color flat display in new applications.

We prove that binary images of irreducible cyclic codes C over GF(2m) and binary concatenated codes of C and a binary [m+1,m,2] even-parity code are optimal (in the sense that they meet the Griesmer bound with equality) and proper, if a root of the check polynomial of C is primitive over GF(2m) or its extensions.

A neuron-MOS transistor (νMOS) is applied to current-mode multi-valued logic (MVL) circuits. First, a novel low-voltage and low-power νMOS current mirror is presented. Then, a threshold detector and a quaternary T-gate using the proposed νMOS current mirrors are proposed. The minimum output voltage of the νMOS current mirror is decreased by VT (threshold voltage), compared with the conventional double cascode current mirror. The νMOS threshold detector is built on a νMOS current comparator originally composed of νMOS current mirrors. It has a high output swing and sharp transfer characteristics. The gradient of the proposed comparator output in the transfer region can be increased 6.3-fold compared with that in the conventional comparator. Along with improved operation of the novel current comparator, the discriminative ability of the proposed νMOS threshold detector is also increased. The performances of the proposed circuits are validated by HSPICE with Motorola 1.5 µm CMOS device parameters. Furthermore, the operation of a νMOS current mirror is also confirmed through experiments on test chips fabricated by VDEC*. The active area of the proposed νMOS current mirror is 63 µm 51 µm.

In this paper, current-mode integrators which consist of only n-channel depletion-mode FET and their application to filters are presented. Lossy integrator is simply realized with a capacitor and a grounded gate FET. Lossless integrator can be obtained by providing a lossy integrator with a positive feedback. To do this, multi-output current mirror is proposed. To reduce 2nd-order harmonic and THD of the filter, unbalanced/balanced conversion circuit is proposed. As an application example, 3rd-order leapfrog low-pass Chebyshev filter is simulated with GaAs MESFET process parameters. Simulation results show good performances.

We investigate the basic properties of focused electron beam (FEB)-damaged Josephson junctions on silicon (Si) substrates for high-frequency device applications. YBa2Cu3O7-y (YBCO) Josephson junction arrays were also fabricated by FEB irradiation to confirm the junction uniformity and to investigate their applicability. The junctions exhibit resistively shunted junction (RSJ)-like current-voltage (I-V) curves and the microwave-induced Shapiro steps for all operation temperatures. Two-junction arrays show single-junction-like behavior with the Shapiro steps in an array up to 2 mV. Microwave-induced Shapiro steps correspond to the double voltages Vn=2nVJ, where VJ=f0h/2e in two-junction arrays. The microwave power dependence of I-V curves shows the steps corresponding to the RSJ model.

The paper obtains an algorithm to estimate the irregular sampling in wavelet subspaces. Compared to our former work on the problem, the new estimate is relaxed for some wavelet subspaces.

We have studied the basic optical and physical characteristics of polymeric optical waveguide films with S-shaped waveguides and 45 mirrors applied as multimode optical interconnection components. The core and cladding of the waveguide films were made of deuterated-polymethylmethacrylate (d-PMMA) and UV-cured resin, respectively. We evaluated the insertion losses of the waveguides, the crosstalk and the 45-mirror losses in these waveguide films and demonstrated that they have low propagation loss. The shrinkage and thermal expansion of the polymeric optical waveguide films are also discussed because of the interest in improving module packaging.

An equivalent circuit for designing a coherent power combiner using a quasi-optical resonator has been developed. In the resonator, large numbers of devices (HEMT, HBT, etc. ) are arrayed two dimensionally and mounted on a surface of a metal grooved-mirror. A newly developed equivalent circuit for the resonator has been constructed using a transmission-line model. Experiments performed at Ku-band have shown that oscillation frequencies in a 33 HEMT array oscillator can be predicted with errors of less than 1% by using this equivalent circuit.

Vehicular speed response phase locked loop (VSR-PLL) is a novel circuit to remove a steady-state frequency offset which arises in the receiver with directive antenna. In this paper, the circuit is applied to Ricean fading environment. For the application of VSR-PLL to Ricean statistics channel, the Doppler shift information of direct wave must be obtained because the self-oscillation frequency of VCO is controlled by using the information. This paper describes an estimation method for the Doppler shift of the direct wave, and shows the several results of the performance analysis for the estimation method and proposed VSR-PLL with the method. As a result, we found that the proposed VSR-PLL could reduce the irreducible bit-error rate for QPSK system from about 10-2 to 10-3 on several conditions.

This paper summarizes our recent efforts in modelocking Ti:sapphire lasers with semiconductor saturable absorber mirrors (SESAMs). We present the shortest optical pulses ever generated directly from a laser. The modelocking build-up time (T BU) of 60 µs is, to our knowledge, the shortest reported for a passively modelocked KLM laser to date.

Area-restricted illumination of light onto a voltage-biased single-electron tunnel junction array is modeled by reduced resistance of junctions, and its effects on current-voltage characteristics, charge distributions and potential profiles are calculated by a Monte Carlo method. The results show that photocurrent nearly proportional to the applied voltage is generated above a threshold voltage determined by Coulomb blockade effect. The photocurrent increases with increasing irradiated area, which is ascribed to reduction in total resistance of the circuit. Under irradiation, a characteristic charge distribution is formed, i. e. , negative and positive charge bumps are formed in the nodes at the dark and bright boundaries. The charge bumps serve to screen the electric field formed by the bias voltage and create almost a flat potential in the irradiated area. Furthermore, time-response of the charge distribution to a pulse irradiation is also studied. For high dark resistance, the charge bumps are sustained for a long period working as a memory of light. These results suggest feasibility of single-electron photonic devices such as photodetectors and photomemories.

Irreducible components of canonical graphs for second order spectral null constraints at a rational submultiple of the symbol frequency fsk/n are studied where fs is the symbol frequency. We show that if n is prime then a canonical graph consists of disjoint irreducible components. We also show that the number of irreducible components of a canonical graphs is finite if n is prime. For the case n = 2 and p O mod n, all aperiodic irreducible components are identified explicitly where p is a parameter of a canonical graph.

The necessary and sufficient conditions for f (x2+x+1) and f (x2+x) to be irreducible, when f (x) is irreducible, are proved. A method that produces polynomials whose roots are linearly independent (therefore form a normal basis for a finite field) is presented.

A high performance, high-swing CMOS cascode current mirror operating with 1V power supply voltage and using standard CMOS technology is presented. The present circuit employs PMOS source-coupled pair as voltage level shifter to reduce the power supply voltage requirement. The additional advantages of the use of the source-coupled pair are the improved output resistance and the automatic adaptive biasing, thereby enabling the high-swing of output terminal, when used in the cascode configuration. An analytical discussion of the circuit is carried out and the results are confirmed by SPICE simulation. SPICE simulation results show that the input voltage requirement is 370mV and the minimum output voltage requirement is 273mV at the maximum input current of 40µA, whose requirements decrease with decreasing input currens. The output resistance is shown to be greater than 4MΩ at the maximum output current of 40µA, which increases with decreasing output currents. The -3dB bandwidth is shown to be greater than 400MHz and the total harmonic distortion better than -54.34dB at 100kHz at the maximum peak-to-peak input current swing of 40µA. The present circuit will be useful for the low voltage, low power, high-performance mixed analog/digital signal processing.

Extremely compact multi-mode interference (MMI) devices using central wide-angle coupling of input and output waveguides are proposed. It is shown that MMI can be used to change the propagation direction of light without the need for corner mirrors or bent waveguides. The concept can also be used for very compact power splitters which are even smaller than conventional MMI power splitters. Coupling between waveguides at wide angles is discussed and a number of regularities are found. The results can be useful for the design of more compact integrated circuits by a reduction of the number of bent waveguides which usually take up the largest part of the area of a photonic integrated circuit.

The growing availability of commercial foundry processes allows easy implementation of micro-opto-electro-mechanical systems (MOEMS) for a variety of applications. Such applications go beyond single devices to include whole optical systems on a chip, consisting of mirrors, gratings, Fresnel lenses and shutters, for example. Hinged and rotating structures, combined with powerful and compact thermal actuators, provide the means for positioning and operating these optical components. This paper presents examples of such systems built in a commercial polycrystalline silicon surface-micromachining process, the ARPA-sponsored Multi-User MEMS ProcesS (MUMPS). Examples range from optical sub-components to large mirror arrays, communication components, and micro-interferometers. Using the examples discussed in this paper, a designer can take advantage of commercially available surface-micromachining processes to design and develop MOEMS without the need for extensive in-house micromachining capabilities.