Structure-dependence of the chirp-to-power ratio spectrum for GaAsexternal cavity lasers

The chirp-to-power ratio (CPR) spectrum has been modeled for GaAs quantum well external cavity lasers. The model includes effects of transverse carrier spatial hole burning, finite carrier transport and capture time from the separate confinement-heterostructure (SCH) region to the quantum well region, and intrinsic material gain compression. The model explains the measured difference of the phase of the CPR at low modulation frequencies between GaAs quantum well and channel-substrate planar (CSP) lasers both in extended cavities. Our results indicate that the carrier effect in the SCH region can make a major contribution to the CPR     

GaAs MESFET laser-driver IC for 1.7-Gbit/s lightwave transmitter

GaAs monolithic integrated circuits for modulating junction lasers (laser drivers) have been developed for a 1.7-Gb/s lightwave communication system. The modulation currents can be varied continuously from a few mA up to 50 or 100 mA, depending on the types of laser drivers. It has been demonstrated that devices of the low-current type are capable of driving a 50-Ω load with a 50-mA modulation current with pulse rise and fall times (10% to 90%) less than 200 ps, and the high-current devices are capable of driving a 25-Ω load with up to 100-mA modulation current with pulse rise and fall times less than 250 ps. Nearly temperature-independent performance has been achieved from 0°C to 70°C. The laser drivers are also capable of providing output DC currents proportional to the duty cycle of input data for the purpose of duty-cycle-independent feedback control of junction lasers. The circuit designs and performance of these devices are described     

Demonstration of a low bandwidth 1.06 μm optical phase-lockedloop for coherent homodyne communication

A type-II, 1.06-μm, optical phase-locked-loop (OPLL) for use in a coherent homodyne receiver is discussed. Diode-laser-pumped solid-state lasers are used for both the local oscillator and transmitter, because their phase noise is significantly lower than that of diode lasers. Closed-loop RMS phase noise of less than 12 mrad (0.69°) is achieved, and modulation-demodulation in bulk modulators at rates from 20 kHz to 20 MHz with less than 19° of modulation depth is demonstrated     

Highly uniform operation of high-performance 1.3-μm AlGaInAs-InPmonolithic laser arrays

We describe the fabrication of monolithically integrated 1×12 arrays of 1.3-μm strain-compensated multiquantum-well AlGaInAs-InP ridge lasers. The laser array shows highly uniform characteristics in threshold current, slope efficiency, and lasing wavelength with a standard deviation of 0.08 and 0.27 mA, 0.012 and 0.007 W/A, and 0.59 and 0.57 nm, respectively, at 20°C and 100°C. Besides, each laser on the array exhibits a low threshold current of 8 mA at 20°C and 21 mA at 100°C, a characteristic temperature of 92 K, and a slope efficiency drop of 0.7 db between 20°C and 80°C. A low thermal crosstalk of less than -4 dB can be obtained from one diode as the injected current of other elements is increased to 70 mA. Also, each laser on the array has a negligible degradation after a 24-hr burn-in test at 80 mA and 100°C. An expected lifetime of more than 20 years is estimated for the lasers when operating at 10 mW and 85°C. The lasers have a small-signal modulation bandwidth of about 9 GHz at 25°C and a low relative intensity noise of -155 dB/Hz without an isolator at 2.5 GHz. It can transmit a 2.5-GHz signal to 50 km through standard single-mode fiber and to 308 m through multimode fiber, with a clear eye opening in OC-48 data-rate tests     

增益饱和对半导体激光器调制特性的影响

本文用小信号分析法建立了半导体激光器调制的数学模拟，用这个模型研究了增益饱和对半导体激光器的功率调制，波长调制和ＣＰＲ值的影响。     

Scalable etched-pillar, AlAs-oxide defined vertical cavity lasers

Etched-pillar, bottom-emitting vertical cavity lasers have been fabricated using lateral oxidation of AlAs. The devices have threshold currents as low as 315 μA for a 4 μm×4 μm, three quantum well active region. Using the data and a numerical model the authors extract excess optical and carrier losses and an effective surface recombination velocity for the devices. The data show that size dependent optical scattering persists as the lasers are scaled to smaller sizes, but lateral carrier leakage is suppressed, allowing for scaling of lasers to small sizes to achieve lower threshold currents     

增益非线性参数对半导体激光器调制特性的影响

本文用小信号分析法建立了半导体激光器调制的数学模拟，用这个模型研究了增益与载流子密度的非线性依赖关系对半导体激光器的功率调制、波长调制和ＣＰＲ值的影响。     

Ultrahigh temperature and ultrahigh speed operation of 1.3 μmstrain-compensated AlGaInAs/InP uncooled laser diodes

High performance 1.3 μm uncooled lasers with excellent high temperature and high speed characteristics are reported. A CW characteristic temperature of 105 K between 25 and 85°C, a maximum CW operating temperature above 170°C, and an intrinsic 3 dB modulation bandwidths estimated at ⩾23 GHz at 25°C and 15 GHz at 85°C, have been achieved. These values are among the best obtained for 1.3 μm AlGaInAs laser devices     

Influence of carrier nonuniformity on the phase relationshipbetween frequency and intensity modulation in semiconductor lasers

The modulus and phase of the chirp to modulated power ratio (CPR) was measured for a 1.5-μm buried-heterostructure laser and a 0.85-μm channeled-substrate planar (CSP) laser. The results for the phase are inconsistent with previously published expressions including spontaneous emission and spectral hole burning. In particular, the CSP laser exhibits an abrupt phase shift in the CPR. An explanation of this behavior is presented in terms of the influence of a nonuniform carrier density on the phase-amplitude coupling, as expressed by an integral expression for the mode parameter α representing the linewidth enhancement factor. Using a simple model for lateral behavior which analytically incorporates diffusion and a nonuniform material α parameter, qualitative agreement was obtained with the CSO data. The authors demonstrate the importance of the lateral laser structure on the phase-amplitude coupling in index-guided semiconductor lasers, and the usefulness of CPR phase measurements for laser characterization     

Approaching intraband relaxation rates in the high-speed modulation of semiconductor lasers

This paper uses a nonequilibrium semiconductor laser model to investigate high-modulation bandwidth operation in semiconductor lasers. In particular, limitations to /spl gsim/100GHz modulation response, which approaches the carrier-phonon scattering rate, are analyzed. It is found that plasma heating leads to a dynamic carrier population bottleneck, which limits scaling of modulation bandwidth. An optical injection scheme is proposed to verify this phenomenon experimentally.     

Frequency modulation of GaAlAs injection lasers at microwave frequency rates

Frequency modulation of GaAlAs double heterostructure injection lasers at microwave frequencies is reported for the first time. The lasers are operating at a 0.85 μm wavelength and have been modulated at frequencies up to 2.25 GHz with a modulation index of 2.4. The laser FM modulation is displayed by a high resolution spectral measuring setup comprising a monochromator and a Fabry-Perot interferometer. A simple laser model is presented which allows the static frequency shift of the laser resonance frequency to be calculated as a function of the bias current change. The results are compared with measured data.     

Pump source requirements for end-pumped lasers

A simple model is developed to relate laser design and properties of a gain medium to the requirements on a pump source for end-pumped lasers or amplifiers. A novel technique for scaling the pump power or energy for end-pumped lasers is presented and analyzed in terms of this model. The results indicate that power or energy scaling of the pump source for end-pumped lasers is not limited by geometry; however, the results also show that some minimum pump energy or power is required     

Room-temperature pulsed operation of triple-quantum-well GaInNAslasers grown on misoriented GaAs substrates by MOCVD

The lasing operation of three-quantum-well GaInNAs stripe geometry lasers grown by MOCVD on 0° and 6° misoriented (100) GaAs substrates, respectively, have been demonstrated and their performance is compared for the first time. Both devices achieved room temperature, pulsed lasing operation at an emission wavelength of 1.17 μm, with a threshold current density of 667 A/cm² for lasers grown on 6° misoriented substrates, and 1 kA/cm² for lasers grown on 0° misoriented substrates. The threshold for the lasers grown on 6° misoriented substrates compares favorably with the best results for GaInNAs lasers. Lasers with narrower stripe width and a planar geometry have also been demonstrated by the use of lateral selective wet oxidation for current confinement, with a threshold current density of 800 A/cm² for 25-μm-wide devices     

High-temperature characteristics of 1.3-μm InAsP-InAlGaAs ridgewaveguide lasers

High-temperature characteristics of InAsP-InAlGaAs strained multiquantum-well (MQW) lasers with a large conduction band discontinuity (ΔE_c) are demonstrated. The InAsP-InAlGaAs MQW ridge waveguide lasers with narrow stripes exhibited a characteristic temperature as high as 143 K in the range from 25°C to 85°C. This material system is promising for developing a cooling-system-free 1.3-μm laser     

Low-threshold tensile-strained InGaAs-InGaAsP quantum-well laserswith single-step separate-confinement heterostructures

The authors studied tensile-strained InGaAs-InGaAsP quantum-well lasers with single-step separate-confinement heterostructures (SCH). They obtained threshold currents below 2 mA at 20°C and below 10 mA at 100°C with indium mole fractions of 0.3 and 0.35 in the active layers. They found that the poorer carrier confinement of the longer wavelength SCH layer lowered the characteristic temperature at high temperatures. A laser with two In_0.35Ga_0.65As wells and a 1.1-μm composition InGaAsP SCH layer produced a 1.6-mA CW threshold current at 20°C and lasing at 120°C. Using this laser, very short lasing delays under zero-bias current over a wide temperature range and 2 Gb/s modulation under zero-bias current at 70°C were achieved     

Low threshold current high-temperature operation of InGaAs/AlGaAsstrained-quantum-well lasers

The authors report improved high-temperature characteristics for In_0.2Ga_0.8As strained-quantum-well ridge waveguide lasers with an optimized cavity design. They have fabricated In_0.2 Ga_0.8As lasers that operate CW at up to 220°C with over 9-mW output power. At 200°C the threshold current is as low as 15.9 mA for a 400-μm-long laser with 35/98% reflectivity facets. Optimization of the laser cavity also improves the high-temperature operation of quantum-well lasers in other material systems; GaAs quantum well lasers that operate at up to 220°C CW have been fabricated     

Strain-compensated 1.3-μm AlGaInAs quantum-well lasers withmultiquantum barriers at the cladding layers

Strain-compensated 1.3-μm AlGaInAs graded-index separate confinement heterostructure (GRINSCH) lasers with multiquantum barrier (MQB) at both the nand p-cladding layers are comprehensively studied and compared with the conventional GRINSCH lasers. It is found that the lasers with MQBs exhibit lower threshold current, higher maximum output power and better temperature characteristics because of the enhanced barrier height for carrier leakage. The characteristic temperature is improved as much as 10 K and the vertical far-field angle is also reduced from 38° to 32° as compared to the conventional counterpart     

A rate equation analysis for the frequency chirp to modulated power ratio of a semiconductor diode laser

An expression for the frequency chirp to modulated power ratio (CPR) is derived from a rate equation analysis of the small-signal, injection current modulation in a semiconductor diode laser. The model includes the effect of lateral carrier diffusion across the active region of the laser diode. The modulation frequency dependence of the CPR is flat from dc to a few hundred megahertz, beyond which it is proportional to the modulation frequency.     

Static and dynamic characteristics of 1.29-μm GaInNAsridge-waveguide laser diodes

Rapid progress has been made in the growth of GaInNAs-GaAs by solid source molecular beam epitaxy, leading to significant improvements of such heterostructures for 1.3-μm wavelength laser emission. We report on growth, device fabrication and characteristics of ridge-waveguide lasers in this material system. Performance data of these devices (emission at λ=1.29 μm, threshold currents of 16 mA, slope efficiencies of 0.35 W/A per facet, and continuous-wave (CW) operation at 100°C) prove that this new material can successfully compete with the well matured InGaAsP-InP system. Furthermore, the very first small-signal modulation measurement results of laser diodes in this novel material-system as well as first ageing results are presented     

High temperature 10 Gbit/s directly modulated 1.3 μm DFB lasersusing InAsP/InGaAsP materials

Uncooled 10 Gbit/s direct modulation of high-power 1.3 μm InAsP/InGaAsP directly modulated multiple quantum well distributed feedback (DFB) lasers is demonstrated. High resonant frequencies and high efficiency at 85°C are obtained due to the high epitaxial quality of ternary, aluminium-free, quantum wells. Floor-free transmission on 90 and 140 ps/nm within ITU recommendations are demonstrated