2-$mu$ m Mode-Locked Semiconductor Disk Laser Synchronously Pumped Using an Amplified Diode Laser

We report a mode-locked antimonide-based semiconductor disk laser operating at 2 $mu$m, synchronously pumped with a pulsed source incorporating a 1.57- $mu$m diode laser, a lithium niobate intensity modulator, and an erbium-doped fiber amplifier. The method for producing the pump signal utilizes commercially available telecom components and allows for convenient selection of the mode-locking harmonics. When compared with configurations based on mode-locked pump sources, the generation of pump pulses using amplitude modulation and digital data technology is simple and offers the possibility to actively lock the optical pulses to a stable clock.      

2.7-$mu$ m GaSb-Based Diode Lasers With Quinary Waveguide

Type-I double-quantum-well (QW) GaSb-based diode lasers operating at 2.7 $mu hbox{m}$ with room-temperature continuous-wave (CW) output power of 600 mW and peak power-conversion efficiency of 10% were designed and fabricated. The devices employed 470-nm-wide AlGaInAsSb waveguide optimized for improved device differential gain. CW threshold current density about 100 $hbox{A}/hbox{cm}^{2}$ per QW and slope efficiency of 150 mW/A were demonstrated at 16 $^{circ }hbox{C}$.      

Bulk Undoped GaAs–AlGaAs Substrate-Removed Electrooptic Modulators With 3.7-V-cm Drive Voltage at 1.55 $mu$ m

Substrate removed bulk GaAs-AlGaAs electrooptic modulators with 3.7-V-cm drive voltage at 1.55 mum were realized. The 1.94-mum-thick undoped GaAs-AlGaAs epilayer removed from its substrate behaves as an electrooptic dielectric layer and has electrodes placed directly on both sides. This allows a very strong modulating electric field overlapping very well with the optical mode. The propagation loss in the presence of electrodes is less than 2.9dB/cm. There is very good agreement between the measured and simulated values     

Rate Equations for 1.3-$mu$ m Dots-Under-a-Well and Dots-in-a-Well Self-Assembled InAs–GaAs Quantum-Dot Lasers

A rate-equation model, in which three discrete quantum-dot (QD) energy levels are assumed and all possible relaxation paths and carrier transport in the GaAs barrier are considered, is presented to analyze the steady-state performance of 1.3 mum undoped and doped dots-under-a-well (DUW) and dots-in-a-well (DWELL) InAs-GaAs QD lasers. DWELL QD lasers have higher saturation value of QD level occupation probabilities and characteristic temperature (T₀) than that of DUW QD lasers due to the improvement of hole confinement. The p-doped QD laser shows lower threshold current density than n-doped QD laser at the same threshold condition, and the T₀ of n-doped DWELL laser is higher than that of p-doped DWELL laser at room temperature. Optimized QD layer number of DUW and DWELL QD lasers with different QD density is discussed     

30 Gb/s Over 100-m MMFs Using 1.1-$mu$ m Range VCSELs and Photodiodes

We developed 1.1-mum-range vertical-cavity surface-emitting lasers based on InGaAs-GaAs quantum wells, back-illuminated InGaAs photodiodes, and transimpedance amplifiers (InP heterojunction bipolar transistor) for high-speed optical interconnection. Clear eye opening operation and error-free transmission at 30 Gb/s over 100-m multimode fibers (GI32) were successfully achieved for the first time.     

A 24-GHz Transmitter With On-Chip Dipole Antenna in 0.13-$mu$m CMOS

A fully integrated dual-conversion transmitter chain with an on-chip dipole antenna and an integer-N synthesizer operating in the 24-GHz Instrument, Scientific and Medical (ISM) band was fabricated in 0.13-mum CMOS. The choice of 24-GHz operation enables the integration of a 4-mm long antenna on chip. The transmitter chain can support data rate of 100 Mb/s. It provides 6-dBm output power to a 100-Omega load at 22.4 GHz with 152-mW power dissipation including that of a frequency synthesizer. At this output power level, the dual conversion architecture can mitigate the VCO pulling even when an antenna and a power amplifier are integrated on the same substrate as the VCO. The out-of-band emissions due to the modulation side lobes and image have been sufficiently suppressed. The stray emissions of local oscillator can also be reduced using circuit techniques. The signal from the transmitter has been picked up 95 meters away with a horn antenna, which suggests that wireless communications between a single chip radio and a base station 100 meters away is possible.     

A 2.5-GHz DDFS-PLL With 1.8-MHz Bandwidth in 0.35-$mu$m CMOS

A wideband frequency synthesizer architecture is presented. The proposed topology employs a direct digital frequency synthesizer (DDFS) to control the output frequency of an offset-PLL. In this way, the synthesizer features a very fine frequency resolution, 24 Hz, as in delta-sigma fractional-N PLLs, but without being affected by the quantization-induced phase noise. This, in turn, allows enlarging the loop bandwidth. The frequency synthesizer is designed to be employed as a direct modulator for Bluetooth transmitter in a low-cost 0.35-mum CMOS technology. At 2.5GHz it achieves 1.8-MHz bandwidth, while the settling time within 30ppm for an 80-MHz step is 3 mus. The integrated phase noise gives less than 1 degree of rms phase error and the worst-case spur is 48dBc at 1 MHz, well below the specifications. Power dissipation is 120 mW for the PLL core, 50 mW for the DDFS plus DACs, and 19 mW for the GFSK modulator.     

High Characteristic Temperature of Highly Stacked Quantum-Dot Laser for 1.55-$mu$ m Band

We fabricated broad-area laser diodes comprising 30-layer stacks of InAs quantum dots (QDs) by using strain compensation. The devices exhibited ground-state lasing at 1529 nm in pulsed mode with a high characteristic temperature of 113 K around room temperature (20 $^{circ}hbox{C}$–80 $^{circ}hbox{C}$). Ground-state lasing was achieved because of the high QD density afforded by strain compensation.      

Room-Temperature p-n-p AlGaAsSb–InGaAsSb Heterojunction Phototransistors With Cutoff Wavelength at 2.5 $mu$ m

Novel p-n-p AlGaAsSb-InGaAsSb heterojunction phototransistors (HPTs) grown by solid-source molecular beam epitaxy have been proposed and demonstrated. The p-n-p phototransistor structure provides a higher emitter injection ratio than its n-p-n counterpart, due to the large conduction band offset and almost continuous valence band edges between InGaAsSb and AlGaAsSb quaternary alloys. The resulting HPT devices exhibit high responsivities under a bias voltage above 0.3 V. A high room-temperature spectral responsivity of 2984 A/W is achieved at 2.24 mum, corresponding to an optical gain of 1652. The 50% cutoff wavelength of spectral photoresponse at room temperature is 2.50 mum. A room-temperature specific detectivity (D^*) of 8.3times10 ¹¹ cm middot Hz^1/2/W is obtained     

A 100-kHz to 20-MHz Reconfigurable Power-Linearity Optimized $G_m$–$C$ Biquad in 0.13-$mu$ m CMOS

Fully reconfigurable transceivers are required to answer the low-power high flexibility demand of future mobile applications. This paper presents a fully reconfigurable G_m-C biquadratic low-pass filter which offers a large range of both frequency and performance flexibility. First, a design approach is proposed focusing on linearity properties by extending Volterra analysis from circuit to architectural level in order to optimize the filters performance. Secondly, a novel switching technique is discussed that allows a bandwidth tuning over more than two orders of magnitude starting from 100 kHz up to 20 MHz and which uses only gate transistor capacitance. Fundamental to this technique is that the power consumption can be traded with the desired performance. Furthermore, the quality factor, noise level and linearity are all programmable over a very wide range. The biquad is processed in a 0.13-mum CMOS technology and operates at different supply voltages down to less than 0.8 V. For a 1.2-V supply, the filter consumes between 103 muA (100 kHz) and 11.85 mA (20 MHz) for a low noise setting around 25 to 35 muVrms integrated over the filter bandwidth achieving an third-order intermodulation intercept point of 10 dBVp.     

Low-Threshold 1.3-$mu$m GaInNAs Quantum-Well Lasers Using Quaternary-Barrier Structures

GaInNAs quaternary-barrier structures, where indium is incorporated to achieve the lattice-matched condition, have been employed for 1.3-m GaInNAs-GaAs single- (SQW) and triple-quantum-well (TQW) lasers. Compared to a GaNAs ternary-barrier structure, photoluminescence results from the quaternary-barrier sample show improved optical properties. Threshold current densities have been achieved with the lowest values of 150 and 529 A/cm² for GaInNAs SQW and TQW lasers at room temperature, respectively.     

1.3-$mu$m Amplifier-Free All-Optical 2R Regenerator Using Two-Mode Injection-Locked Distributed Feedback Laser Diode

This study presents a novel and cost-effective 1.3-mum all-optical 2R regenerator based on a two-mode injection-locked distributed feedback laser diode. The proposed 2R regenerator, with 14.13-dB small signal gain, has achieved an amplifier-free 10-Gb/s straight line transmission over 60 km while keeping the power penalty less than 0.84 dB at bit-error rate (BER) =10^-9. In addition, properties like BER degradation, output extinction ratio, gain, and data-rate transparency are also experimentally investigated     

Optical Absorption Glucose Measurements Using 2.3-$mu$m Vertical-Cavity Semiconductor Lasers

Continuous glucose monitoring has been shown to help diabetes mellitus patients stabilize their glucose levels, leading to improved patient health. One promising technique for monitoring blood glucose concentration is to use optical absorption spectroscopy. This letter proposes the use of thermally tunable 2.3-mum vertical-cavity surface-emitting lasers to obtain blood absorption spectra. The partial least squares technique is used to determine the glucose concentration from the spectra obtained in aqueous glucose solutions.     

Self-Oscillation Free 0.35 $mu$ m Si/SiGe BiCMOS X-Band Digital Frequency Divider

This letter reports a digital master-slave D-type register divide-by-512 frequency divider designed in a 0.35 Si/SiGe BiCMOS technology. The 600times1200 mum² circuit operates up to 9.5 GHz dissipating 120 mW. Self-oscillations are avoided by the use of a radio frequency carrier detector that controls the bias of the last six registers.     

Quantum-Dot Semiconductor Optical Amplifiers With Polarization-Independent Gains in 1.5-$mu$ m Wavelength Bands

We have demonstrated a polarization-independent gain in semiconductor optical amplifiers that have columnar quantum dots surrounded by strained side barriers in 1.5-$mu$ m wavelength bands. We obtained a polarization-dependent gain of 0.5 dB with a gain of 10 dB and a saturation output power of 18 dBm at a wavelength of 1.55 $mu$ m.      

A 40-Gb/s Transimpedance Amplifier in 0.18-$mu$m CMOS Technology

A 40-Gb/s transimpedance amplifier (TIA) is realized in 0.18-mum CMOS technology. From the measured S-parameters, a transimpedance gain of 51 dBOmega and a 3-dB bandwidth up to 30.5 GHz were observed. A bandwidth enhancement technique, pi-type inductor peaking (PIP), is proposed to achieve a bandwidth enhancement ratio (BWER) of 3.31. In addition, the PIP topology used at the input stage decreases the noise current as the operation frequency increases. Under a 1.8 V supply voltage, the TIA consumes 60.1 mW with a chip area of 1.17 X 0.46 mm2. The proposed CMOS TIA presents a gain-bandwidth product per DC power figure of merit (GBP/P_de) of 180.1 GHzOmega/mW.     

All-Silicon 1.55-$mu$m High-Resolution Photon Counting and Timing

We investigate the performances at 1.55- $mu{hbox{m}}$ wavelength of silicon single photon avalanche diodes (SPADs), demonstrating their suitable applicability in laser characterizations and ultra-sensitive autocorrelation measurements. We investigate the photon detection efficiency and the two-photon absorption process of both lightly doped thick SPADs and heavily doped thin SPADs. Finally, we report the accurate pulse-shape characterization of a 1.55- $mu{hbox{m}}$ pulsed laser by means of a thin silicon SPAD that exploits the best intrinsic time resolution of 25 ps with wide dynamic range and low measurement time.      

Bipolar Cascade Superluminescent Diodes at the 1.04-$mu$m Wavelength Regime

In this study, we investigate the performance of GaAs-based bipolar cascade superluminescent diodes with different cavity lengths. The device operates around the important bio-optical therapeutic 1.04- $muhbox{m}$ wavelength window. The introduction of tunnel junctions tends to minimize the nonuniform carrier distribution between distinct multiple quantum-wells (QWs), which is a problem in conventional SLDs, whose electroluminescent spectra are governed by the center wavelength of QWs near the p-side. Our devices exhibit nice electrical characteristics of low leakage current and overcome the limitation of nonuniform carrier distribution, thereby presenting a promising prospect for the near infrared white-light sources.      

Packaged 1.5-$mu$ m Quantum-Well SOA With 0.8-W Output Power and 5.5-dB Noise Figure

We report the demonstration of a lensed-fiber- pigtailed InGaAsP–InP quantum-well semiconductor optical amplifier based on the slab-coupled optical waveguide (SCOW) concept. At a 5-A bias current and a wavelength of 1540 nm, the packaged SCOW amplifier (SCOWA) exhibits a record 0.8-W saturation output power, 13.8-dB small-signal gain, 5.5-dB noise figure, and a maximum electrical-to-optical conversion efficiency of 11%. The estimated coupling efficiency between the large (5.6 $,times,$7.5 $mu$m), fundamental SCOWA mode and the lensed fibers (6.5-$mu$ m spot size) is 90%.      

Optical Injection-Induced Polarization Switching Dynamics in 1.5-$mu$m Wavelength Single-Mode Vertical-Cavity Surface-Emitting Lasers

We report the first experimental invetigation of the polarization-mode switching dynamics and injection-wavelength-dependent polarization-mode bistability of a 1.5-m wavelength single-mode vertical-cavity surface-emitting lasers (VCSELs) under external laser beam injection. An injection beam with polarization orthogonal to that of the stand-alone VCSEL caused polarization-mode instability and switching of the VCSEL output. By varying the optical injection detuning for fixed injection power observation was made of a novel form of polarization bistability which will have applications in a new type of all-optical flip-flop and signal processing scheme.