We demonstrated all-optical demultiplexing of 160-Gb/s signal to 40- and 80-Gb/s by a Mach-Zehnder Interferometric all-optical switch, where the picosecond cross-phase modulation (XPM) induced by intersubband excitation in InGaAs/AlAsSb coupled double quantum wells is utilized. A bi-directional pump configuration, i.e., two control pulses are injected from both sides of a waveguide chip simultaneously, increases a nonlinear phase shift twice in comparison with injection of single pump beam with forward- and backward direction. The bi-directional pump configuration is the effective way to avoid damaging waveguide facets in the case where high optical power of control pulse is necessary to be injected for optical gating at repetition rate of 40/80 GHz. Bit error rate (BER) measurements on 40-Gb/s demultiplexed signal show that the power penalty is decreased slightly for the bi-directional pump case in the BER range less than 10^-6. The power penalty is 1.3 dB at BER of 10 ^{- 9} for the bi-directional pump case, while it increases by 0.3-0.6 dB for single pump cases. A power penalty is influenced mainly by signal attenuation at "off" state due to the insufficient nonlinear phase shift, upper limit of which is constrained by the current low XPM efficiency of 0.1 rad/pJ and the damage threshold power of 100 mW in a waveguide facet.

We fabricated high-power pure blue laser diodes (LDs) by using GaN-based material for full-color laser display. The operating output power, voltage and wall-plug efficiency of the LDs at forward current of 1.0 A were 1.17 W, 4.81 V and 24.3%, respectively. The estimated lifetime of the LDs was over 30,000 hours under continuous-wave operation.

We have proposed a tunable laser with silica-waveguide ring resonators. In this tunable laser, a semiconductor optical amplifier was passively aligned and mounted onto a silica-waveguide substrate. The ring resonators can be tuned by controlling their temperatures using the thermo optic heaters formed on them, and there are no mechanically moving parts. Thus, they are sufficiently stable and reliable for practical use. Our tunable laser exhibits a high fiber-output power of more than 15 dBm and a wide tunable range of 60 nm (L-band, 50 GHz spacing, 147 channels). Moreover, a tunable laser with a much wider tunable range of 96 nm using 100-GHz-FSR ring resonators is also reported.

We present a dual traveling-wave electrode InP-based Mach-Zehnder (MZ) modulator with an n-i-n waveguide structure. An electrical input/output interface placed on one side of the chip helps us to drive the modulator in a push-pull configuration. This configuration provides the modulator with great advantages such as reduced driving voltage amplitude, chirp-free operation, and the ability to support advanced modulation formats. The fabricated modulator exhibits good performance. A 40 Gb/s non-return-to-zero (NRZ) signal is successfully generated with a low driving of 1.3 V_pp. In addition, a 10-Gb/s optical duobinary (DB) signal is successfully generated and transmitted over a 240-km single-mode fiber (SMF). We also developed a wavelength tunable transmitter hybrid integrated with a modulator with a wavelength tunable laser. Full C-band 10-Gb/s operation and a 100-km SMF transmission with a low power penalty are confirmed.

A new LiTaO₃ electro-optic polarization modulator utilizing traveling-wave electrodes and a double periodic poling structure is proposed. Utilizing the double periodic poling structure, both quasi-phase matching between TE and TM guided-modes, and quasi-velocity matching between a lightwave and a modulation microwave are obtainable at modulation frequencies over 10 GHz.

Silicon photonic devices based on silicon photonic wire waveguides are especially attractive devices, since they can be ultra-compact and low-power consumption. In this paper, we demonstrated various devices fabricated on silicon photonic wire waveguides. They included optical directional couplers, reconfigurable optical add/drop multiplexers, 12, 14, 18 and 44 optical switches, ring resonators. The characteristics of these devices show that silicon photonic wire waveguides offer promising platforms in constructing compact and power-saving photonic devices and systems.

This paper reviews our recent progress on arrayed waveguide gratings (AWGs) using super-high-Δ silica-based planar lightwave circuit (PLC) technology and their application to integrated optical devices. Factors affecting the chip size of AWGs and the impact of increasing relative index difference Δ on the chip size are investigated, and the fabrication result of a compact athermal AWG using 2.5%-Δ silica-based waveguides is presented. As an application of super-high-Δ AWGs to integrated devices, a flat-passband multi/demultiplexer consisting of an AWG and cascaded MZIs is presented.

This paper focuses on optical integration technology and its application in optical microsensors used in biomedical fields. The integration is based on the hybrid integration approach, achieving high performance, small size and weight, and lower cost. First, we describe the key technologies used in hybrid integration, namely passive alignment technology, low temperature bonding technology, and packaging technology for realizing advanced microsensors. Then, we describe an integrated laser Doppler flowmeter that can monitor blood flow in human skin.

We propose a gap-less optical interconnection between BGA package and board for practical on-board, chip-to-chip optical interconnection. The optical interconnect consists of polymer optical waveguides, an integral mirror on the PWB (printed wiring board), an optical via hole through package, and a connection structure and method requiring no alignment process. Optical waveguide, mirror, waveguide extensions and alignment studs were fabricated on the PWB as horizontal optical interconnect. Coaxial structured optical vias with core and cladding were formed through the package and with precise holes for alignment. Two packages were attached onto the PWB using standard BGA technology utilizing passive optical alignment. The optical characteristics and 10 Gbit/s open-eye diagram were measured. A completely gap-less three dimensional optical interconnect between package-PWB-package was demonstrated.

An AuSn reflow process using hydrogen radicals as a way to avert the cleaning of flux residues was investigated for its application to solder bumping. AuSn particles (manufactured by a gas atomizer) smaller than 5 µm, which are difficult to reflow by conventional methods that use rosin mildly activated (RMA) flux, were used for the experiments. In this process, the reduction effect by the hydrogen radicals removes the surface oxides of the AuSn particles. Excellent wetting between 1-µm-diameter AuSn particles and Ni metallization occurred in hydrogen plasma. Using hydrogen radicals, 100 µm-diameter AuSn bumps without voids were successfully formed at a peak temperature of 300. The average bump shear strength was approximately 73 gf/bump. Bump inspection after shear testing showed that a fracture had occurred between the Au/Ni/Cr under bump metallurgy (UBM) and Si substrate, suggesting sufficient wetting between the AuSn bump and the UBM.

This paper analyzes the spurious sources in DDS synthesizers and deduces the simple model of DDS output signal. The method of feeding pseudo-random noise into the phase accumulator for spurious reduction is discussed. A new method for spurious reduction by compensating for DAC integer nonlinearity is proposed with two DACs and a power combiner. One DAC generates the error signal to compensate for the other DAC INL. The factor how the amplitude error and the phase error between the two combined signals affect the spurious level is also analyzed. The experiment shows that the spurious reduction can be improved by at least 18 dB, which proves the validity of the DAC INL compensation method for the spurious reduction.

This paper investigates and analyzes the resistive averaging network and interpolation technique to estimate the power consumption of preamplifier arrays in a flash analog-to-digital converter (ADC). By comparing the relative power consumption of various configurations, flash ADC designers can select the most power efficient architecture when the operation speed and resolution of a flash ADC are specified. Based on the quantitative analysis, a compact 5-bit flash ADC is designed and fabricated in a 0.13-µm CMOS process. The proposed ADC consumes 180 mW from a 1.2-V supply and occupies 0.16-mm² active area. Operating at 3.2 GS/s, the ENOB is 4.44 bit and ERBW 1.65 GHz. At 4.2 GS/s, the ENOB is 4.20 bit and ERBW 1.75 GHz. This ADC achieves FOMs of 2.59 and 2.80 pJ/conversion-step at 3.2 and 4.2 GS/s, respectively.

We identify a broadband equivalent circuit of an on-chip self-complementary antenna integrated with a µm-sized semiconductor mesa structure whose circuit elements can be interpreted by using closed-form analysis. Prior to the equivalent circuit analysis, an electromagnetic simulation is done to investigate frequency independency of the input impedance for the integrated self-complementary antenna in terahertz range.

In this paper, a criterion for nonlinear stability analysis of microwave oscillator has been devised. The circuit envelope method has been used for analyzing the perturbed circuit. The proposed approach is evaluated by analyzing the nonlinear stability of a practical FET oscillator.

A general-purpose multi-Gbps LVDS driver is presented with a new distortion-free level conversion scheme. For high-speed transmission, a dynamic pre-emphasis scheme is also proposed with overdriving current effectively distributed in time. The proposed LVDS driver achieves supply-insensitive duty preservation with a reduction of switching noise by 50-percent.

Body-biasing is expected to be a common design technique, and then area efficient implementation in layout has been demanded. Body-biasing outside standard cells is one of possible layouts. However in this case body-bias controllability, especially when forward bias is applied, is a concern. To investigate the controllability, we fabricated and measured a ring oscillator in a 90 nm technology. Our measurement result and evaluation of area efficiency reveal that body-biased circuits can be implemented with area overhead of less than 1% yet with sufficient speed controllability.