1.3-μm Quantum-Dot Multisection Superluminescent Diodes With Extremely Broad Bandwidth

A novel ridge-waveguide quantum-dot superluminescent diode is reported. The multisection configuration enables the simultaneous realization of ultrawide 3-dB bandwidth (>150 nm) and an output power greater than 1 mW     

High-Power 1.3-μm Quantum-Dot Superluminescent Light-Emitting Diode Grown by Molecular Beam Epitaxy

In this letter, we demonstrate the improved performance of 1.3-mum seven-layered InAs-GaAs quantum-dot superluminescent light-emitting diodes by the engineering of the epitaxial growth conditions alone, namely the thickness of the low-temperature GaAs spacer layer between quantum-dot layers. For laser devices, a significant reduction in threshold current density and increase in external efficiency is observed, while for superluminescent diode structures, a ~4 fold increase in CW power at a given drive current is obtained     

Systematic Study of the Effects of Modulation p-Doping on 1.3-μm Quantum-Dot Lasers

The effects of modulation p-doping on 1.3-mum InGaAs-InAs quantum-dot (QD) lasers are systematically investigated using a series of wafers with doping levels from 0 to 18 acceptors per QD. Various characterization techniques for both laser diodes and surface-emitting light-emitting diode structures are employed. We report: 1) how the level of modulation p-doping alters the length dependant laser characteristics (in turn providing insight on various key parameters); 2) the effect of modulation p-doping on the temperature dependence of a number of factors and its role in obtaining an infinite T₀; 3) how increasing concentrations of modulation p-doping affects the saturated gain, differential gain, and gain profile of the lasers; and finally, 4) the effect modulation p-doping has on the small signal modulation properties of 1.3-mum QD lasers. In each of these areas, the role of modulation p-doping is established and critically discussed.     

1.6-μ m Multiwavelength Emission of an InAs–InGaAsP Quantum-Dot Laser

A multiwavelength laser with maximum signal-to-noise ratio up to 62 dB was demonstrated on the basis of a 461-m-long InAs-InGaAsP quantum-dot waveguide Fabry-Perot cavity chip. It has 24 channels with 0.8-nm channel spacing and 8.0-dB maximum channel intensity nonuniformity over a wavelength range from 1612 to 1632 nm. Its channel spacing irregularity due to linear intracavity waveguide dispersion was also investigated.     

High-Temperature Continuous-Wave Operation of GaInAsN–GaAs Quantum-Dot Laser Diodes Beyond 1.3 μm

Internal laser parameters and characteristic temperature T₀ of a GaInAsN-GaAs quantum-dot (QD) laser emitting above 1350 nm were determined. Continuous-wave operation of GaInAsN-GaAs QD ridge waveguide laser diodes with an emission wavelength of 1355 nm at room temperature (RT) is reported for the first time. Low threshold currents of 16 mA are achieved at RT. Ground state laser emission is observed up to temperatures of 75degC with a resulting laser emission wavelength of 1395 nm.     

Dynamics and Temperature-Dependence of 1.3-μm GaInNAs Double Quantum-Well Lasers

We have measured the small-signal modulation response of 1.3-mum ridge waveguide GaInNAs double quantum-well lasers over a wide range of temperatures (25 degC-110 degC) and analyzed the temperature dependence of the modulation bandwidth and the various bandwidth limiting effects. The lasers have low threshold currents and high differential efficiencies with small temperature dependencies. A short-cavity (350 mum) laser has a modulation bandwidth as high as 17 GHz at room temperature, reducing to 4 GHz at 110 degC, while a laser with a longer cavity (580 mum) maintains a bandwidth of 8.6 GHz at 110 degC. We find that at all ambient temperatures the maximum bandwidth is limited by thermal effects as the temperature increases with current due to self-heating. The reduction and subsequent saturation of the resonance frequency with increasing current is due to a reduction of the differential gain and an increase of the threshold current with increasing temperature. We find large values for the differential gain and the gain compression factor. The differential gain decreases linearly with temperature while there is only a weak temperature dependence of the gain compression. At the highest temperature we also find evidence for transport effects that increase the damping rate and reduce the intrinsic bandwidth     

High-Performance Directly Modulated 1.3- μm Undoped InAs–InGaAs Quantum-Dot Lasers

In this letter, we report on experimental results of directly modulated single-transverse mode 1.3-mum InAs-InGaAs quantum-dot (QD) lasers in a wide temperature range. A 3.125-Gb/s data modulation over temperature with an extinction ratio up to 10 dB is reported. Moreover, 10-Gb/s eye patterns at 15 degC and 50 degC and 5-Gb/s modulation in the whole explored temperature range (15 degC-85 degC) are demonstrated. These results were obtained by exploiting heterostructures containing six layers of high modal gain InAs QDs grown without incorporation of p-doping in the active region or tunnelling injection structure implementation. QD lasers exhibited a saturation modal gain as high as 36.3 cm^-1, ground state lasing from short cavities down to 400-mum length and a characteristic temperature of about 110 K in a large temperature range between 15 degC and 85 degC     

Analysis of the Double Laser Emission Occurring in 1.55-μm InAs–InP (113)B Quantum-Dot Lasers

In this paper, a theoretical model based on rate equations is used to investigate static and dynamic behaviors of InAs-InP (113)B quantum-dot (QD) lasers emitting at 1.55 mum. More particularly, it is shown that two modelling approaches are required to explain the origin of the double laser emission occurring in QD lasers grown on both, GaAs and InP substrates. Numerical results are compared to experimental ones by using either a cascade or a direct relaxation channel model. The comparison demonstrates that when a direct relaxation channel is taken into account, the numerical results match very well the experimental ones and lead to a qualitative understanding of InAs-InP (113)B QD lasers. Numerical calculations for the turn-on delay are also presented. A relaxation oscillation frequency as high as 10 GHz is predicted which is very promising for the realization of directly modulated QD lasers for high-speed transmissions.     

A 2.2-μm-Pitch Single-Transistor Charge-Modulation Pixel in a 0.13-μm CMOS Process

This paper presents the investigation of a 2.2-mum-pitch single-transistor pixel designed in a 0.13-mum CMOS process. Based on charge-induced potential variation of the floating-body of the transistor, this single pixel device can be operated to perform photodetection, charge integration, signal readout, and reset. The main electrical characteristics of the pixel are evaluated by device modeling and simulations as well as measurements of test chips. With optimization of process and electrical parameters, testing results show a conversion factor of 47 muV/hole, a charge-handling capability of 3500 holes, a temporal noise of four holes, and a dynamic range of 40 dB.     

Intrinsic Dynamic Properties of High-Characteristic Temperature GaInNAs Laser Diodes Operating at 1.3 μm

The properties of a high-characteristic temperature (T₀=155K) 1.3-mum GaInNAs-GaAs laser are presented with an emphasis on laser dynamic characteristics evaluated by linewidth enhancement factor and relative intensity noise. It is found that the relatively high differential gain of GaInNAs-GaAs quantum wells leads to a small linewidth enhancement factor of 2.8, indicating a small magnitude of frequency modulation with modulation current. The relative intensity noise measurements indicate a relaxation frequency of 4.7 GHz at a moderate bias current, from which the maximum intrinsic modulation bandwidth was calculated to be 9.7 GHz. The experimental determination of the low linewidth enhancement factor and high relaxation frequency reinforce the potential of dilute nitride lasers for high-speed directly modulated fiber links     

Differential Temperature Sensors Fully Compatible With a 0.35-μm CMOS Process

Four differential temperature sensors, two passive and two active, designed and fabricated in a 0.35-m standard CMOS technology, are presented and characterized. Passive sensors are based on integrated thermopiles. Each one consists of eight thermocouples (16 strips) serially connected: poly1-poly2 for the first thermopile and poly1-P+diffusion for the second one. The active sensors are based on differential amplifiers, one with single-ended output and the other with differential output. Lateral parasitic bipolar transistors are used as temperature transducer devices. Both simulated and experimental characterizations are presented. The high sensitivity of active differential temperature sensors proves the feasibility of such sensors to observe the power dissipated by devices and circuits embedded in the same silicon die, with applications to the test and characterization of circuits, packaging characterization and compensation of thermal gradients, among others.     

Characterization and Modeling of Broad Spectrum InAs–GaAs Quantum-Dot Superluminescent Diodes Emitting at 1.2–1.3 μm

High-power broadband superluminescent diodes (SLDs) emitting in the 1.2-1.3-mum region are demonstrated using InAs-GaAs quantum dots (QDs). The highest output powers of ~30-50 mW are achieved using 18 QD layers with p-doped GaAs spacers. At these high powers the device operates in a regime of broad bandwidth (~100 nm) with a spectral dip of ~5 dB between two separate peaks originated by the QD ground and excited states. Spectral calculations performed with a traveling-wave rate equation model show excellent agreement with the experimental data and provide design rules for optimizing the output spectrum. SLD characteristics are presented for two different device structures consisting of tilted and bent waveguides. The latter allows the achievement of higher output powers at lower currents. The coherence properties and the temperature characteristics are also discussed in detail.     

Highly Reliable 1.5-μm DFB Laser With High-Mesa SIBH Structure

The degradation behavior of 1.5-mum uncooled distributed feedback (DFB) lasers with a semi-insulating buried heterostructure during constant-power aging is investigated. Long-term stability is achieved by suppressing the t^0.5 deterioration in the current increase rate (second-stage degradation). The improvement in reliability is attributed to the fact that some defects on the grating interface are simultaneously suppressed by the mutual diffusion that occurs when growing the SI-InP layer. We realized a DFB laser with high reliability (< 1000 failure digits) at 95 degC that is capable of error-free 2.5-Gb/s 80-km transmission at -20degC to 100 degC     

1.3-μm GaInAsN Vertical-Cavity Surface-Emitting Lasers by Oxide-Planarized and Surface-Relief Processes for Single-Mode Operation

In this letter, we investigate and characterize the 1.3-mum single-mode vertical-cavity surface-emitting lasers (VCSELs) with two GaInAsN strained multiple quantum wells as the active region. Surface relief technique and a thick silicon oxide were used for the spatial mode filtering and the planarization processing, respectively. The VCSELs with a 5-mum-diameter surface-relief aperture and a 12-mum-diameter oxide-confined aperture at room temperature exhibit a threshold current of 3 mA, a slope efficiency of 0.14 mW/mA, a maximum operation temperature of 90 degC, and a single-mode behavior. These VCSELs show a maximum light output power of 1 mW for the single fundamental mode with a transverse-mode suppression of more than 30 dB and also show a clear eye-opening feature operated at 2.488 Gb/s and 12.6 mA     

Degradation Analysis of 2-μm DFB Laser Using Optical Beam-Induced Current Technique

The degradation behavior of 2-mum wavelength distributed feedback lasers with a p- and n-type InP buried heterostructure during constant-power aging is investigated. The degradation mechanism is governed by diffused defects with a parallel direction in the crystal plane. Furthermore, it is clarified that the epitaxial layers on the mesa affect both first- and second-stage degradations.     

1.3–1.55-μ m CMOS/InP Optoelectronic Receiver Using a Self-Aligned Wafer Level Integration Technology

A heterogeneous 10-Gb/s 1.3- to 1.55-mum optoelectronic receiver is designed and fabricated using a complementary metal-oxide-semiconductor transimpedance amplifier and an InGaAs-InP PIN (p-type, intrinsic, n-type diode) photodiode. The receiver is heterogeneously integrated based on a batch fabrication process which promises low fabrication cost. The receiver measures a transimpedance gain of higher than 50 dBldrOmega over a bandwidth of 6 GHz and demonstrates an open eye diagram with a 1.55-mum 10-Gb/s light source.     

Optical properties of a 1.3-µm InGaAsP superluminescent diode

The optical properties of a 1.3-µm InGaAsP-InP buried heterostructure (BH) superluminescent diode (SLD) are described. The spectra of this device exhibit a large number of longitudinal modes. The light output at constant current from an SLD has a strong temperature dependence in the superluminescent region (high currents) and week temperature dependence in the spontaneous region (low currents). This severe temperature dependence will limit the systems application of this type of device unless thermoelectric cooling is used. The coupling efficiency (butt-coupling) into a 0.23-NA 50-µm-diameter graded index fiber is 26 percent. A model of the SLD including a temperature dependent nonradiative mechanism (same as in 1.3-µm InGaAsP lasers) suggests that the strong temperature dependence in the superluminescent region is a fundamental property of the device.     

1.3-μ m InGaAlAs Short-Cavity DBR Lasers for Uncooled 10-Gb/s Operation With Low Drive Current

We present a novel 1.3-mum laser, a short-cavity distributed-Bragg-reflector (DBR) laser that enables uncooled, 10-Gb/s operation with low drive currents. The laser consists of a short InGaAlAs multiple-quantum-well active region butt-jointed to an InGaAsP-DBR region. A fabricated laser with a 75-mum active region demonstrated 100 degC, 10-Gb/s operation at a record low drive current of 14-mA peak-to-peak (mA_p-p) with an average output power of -3 dBm     

A 0.13-μ m CMOS Phase Shifter Using Tunable Positive/Negative Refractive Index Transmission Lines

This letter presents a tunable positive/negative refractive index transmission line (TL) phase shifter utilizing active circuits. It comprises a microstrip TL loaded with series varactors and a shunt monolithic microwave integrated circuit (MMIC) to synthesize a tunable inductor. This implementation increases the phase tuning range and maintains the input and output matching of the phase shifter across the entire phase tuning range, while eliminating the need for bulky passive inductors. The phase shifter is capable of providing both positive and negative phase shifts. The MMIC tunable inductors are fabricated in a 0.13-mum CMOS process and operate from a 1.5-V supply. The phase shifter achieves a phase of -40deg to +34deg at 2.5GHz from a single stage with less than -19dB return loss, and better than 1.1-dB insertion loss at 2.5 GHz. The phase shifter has a 1-GHz bandwidth over which the return loss remains better than 12.1dB     

A 1.3-µm microwave fiber-optic link using a direct-modulated laser transmitter

A 1.3-μm 1.1-km-long single-mode fiber-optic link with a 4.1-4.7 GHz frequency response has been developed. This is one of the highest freqUency fiber-optic links reported to date. A 60-dB SNR, ±1.0-dB gain flatness, and 44-dB spur-free dynamic range was observed. The performance of this link is primarily determined by the direct-modulated laser transmitter. This paper discusses the design of that component along with the development and performance of the complete fiber-optic link.