The high-speed limit of FM response in semiconductor lasers

The high-speed frequency modulation (FM) response has been investigated through rate equation analysis. The intrinsic limit of FM response has been found to be given by the product of FM efficiency, η_FM, and the FM bandwidth, B. This relation shows that a wide FM bandwidth means a small FM efficiency. Although the FM efficiency changes with the differential gain or the nonlinear gain coefficient, η_FMB is almost constant. The value of η _FMB was about 5 GHz²/mA for 1.5-μm InGaAsP/InP lasers with 300-μm cavity length. This limit has been confirmed experimentally     

A 10-s doping technology for the application of low-temperaturepolysilicon TFTs to giant microelectronics

A bucket-type high-density (0.25-1.2-mA/cm²) low-energy (500-2000 V) ion source was utilized for high-speed phosphorus doping directly into a thin polysilicon layer without cap SiO₂. Doping gas with He dilution was selected to reduce etching of polysilicon film. Excimer laser (XeCl, 8 mm×8 mm) pulse annealing was introduced to activate effectively the doped impurity. The combination of these techniques provided a practically low sheet resistance for the TFT source, drain, and gate with a short time doping. The low-temperature polysilicon TFT fabricated with a doping time of 10 s had characteristics comparable to those of that fabricated by a longer time doping or conventional ion implantation, showing the practicality of this technology and its promise for giant microelectronics     

IN rollout in Japan

The evolution of the intelligent network (IN) services and architecture of the Nippon Telegraph and Telephone Public Corporation (NTT) is discussed. The hierarchical structure of network functions, machine independent service execution environment, advanced service creation environment and service-independent platform of the IN architecture are reviewed. Advanced IN's impact and the technical issues that remain unsolved are described     

Experimental demonstration of soliton data transmission over unlimited distances with soliton control in time and frequency domains

A 2/sup 9/-1 pseudorandom-binary-sequence soliton signal has been transmitted experimentally over one million km for the first time with no degradation in the bit error rates. The synchronous modulator was driven by a timing clock signal extracted from the transmitting data signal. These results mean that it is possible to send soliton data signals over unlimited distances through the use of soliton control in the time and frequency domains.<>     

A circuit technology for high-speed battery-operated 16-Mb CMOSDRAM's

A battery-operated 16-Mb CMOS DRAM with address multiplexing has been developed by using an existing 0.5-μm CMOS technology. It can access data in 36 ns when powered from a 1.8-V battery-source, and 20 ns at 3.3 V. However, this device requires a mere 57 mA of operating current for an 80-ns cycle time and only 5 μA of standby current at 3.3 V. To achieve both high-speed and low-power operation, the following four circuit techniques have been developed: 1) a parallel column access redundancy (PCAR) scheme coupled with a current sensing address comparator (CSAC), 2) an N&PMOS cross-coupled read-bus-amplifier (NPCA), 3) a gate isolated sense amplifier (GISA) with low V_T, and 4) a layout that minimizes the length of the signal path by employing the lead on chip (LOC) assembly technique     

Fabrication of 64×64 arrayed-waveguide grating multiplexer onsilicon

A 64 channel arrayed-waveguide multiplexer with 0.4 nm (50 GHz) channel spacing at 1.55 μm has been fabricated using SiO₂-Si waveguides. The authors obtained a crosstalk of less than -27 dB to neighbouring and all other channels. The on-chip insertion loss ranges from 3.1 to 5.7 dB for central and peripheral output ports, respectively     

10 Gbit/s, 1200 km error-free soliton data transmission using erbium-doped fibre amplifiers

Soliton data signals at 10 Gbit/s have been successfully transmitted for the first time through a 1200 km dispersion-shifted fibre by using 24 erbium-doped fibre amplifiers. A bit error rate below 10/sup -13/ was obtained with 2/sup 20/-1 pseudorandom patterns.<>     

A monolithic three-channel LD-PD array with vertically staggeredfacets for autofocusing reflectivity sensors

A monolithic three-channel LD-PD array with vertically staggered facets is proposed for an autofocusing reflectivity sensor which uses light feedback. The focus-sensing characteristics are investigated using an array with a radiation facet displacement of 12 μm and an interchannel distance of 130 μm, fabricated on an 830-nm AlGaAs/GaAs multiple-quantum-well laser substrate with buried-heterostructure stripe geometry waveguides. High focus-sensing accuracy is achieved. A potential application of the array to optical heads for phase change media is discussed     

Infinite-distance soliton transmission with soliton controls in time and frequency domains

It is shown by computer runs and simple analysis that one hundred million km soliton transmission is possible by means of soliton transmission controls in the time and frequency domains. This means that limitless transmission is possible. The key to success is to reduce noise by the synchronous modulation technique which can also reduce timing jitter and nonlinear interaction forces. The accumulated noise converges to a fixed low level even after limitless transmission.<>     

Dependence of the frequency shift of the optical-microwave doubleresonance signal in the Cs D2 line on the pumpingfrequency and power of a GaAs semiconductor laser

The OMDR (optical-microwave double resonance) effect in the Cs D₂ line was studied for realizing a gas-cell-type Cs atomic frequency standard. A glass cell containing Cs with buffer gases (Ar/N₂=1.26, total pressure=39 torr) was placed in a TE₀₁₂ mode microwave cavity at a temperature of 45°C and was pumped using a GaAs semiconductor laser frequency locked to an external interferometer tuned to the 6P_3/2 (F=2,3,4)←6 S_1/2(F=3) transition. The OMDR signal appearing at the resonance to the F=4←3 hyperfine transition of the 6S_1/2 state shifted with detuning of the laser frequency and with change of the laser and microwave powers. The dependence of the shift on these variables around an optimum operating condition was obtained as, Δν_MW[Hz]=-(0.31±0.02) {1+(0.44±0.15) (ΔP_L/P_L)} Δν_L [MHz]-10(ΔV_MW/V _MW)