Two-dimensional simulation of constricted-mesa InGaAsP/InPburied-heterostructure lasers

A fully two-dimensional self-consistent numerical model of the steady-state behavior of 1.3 μm constricted-mesa InGaAsP/InP buried-heterostructure lasers is presented. Devices operating at this wavelength are very temperature sensitive and therefore the model for the first time includes coupled solutions to the thermal as well as the electrical and optical equation sets. The temperature dependence is included in the Fermi-Dirac statistics, bandgaps, mobilities, densities of states, Auger recombination coefficients, intervalence band absorption, optical gain, and thermal conductivities. The lasing mode profiles, carrier distributions, threshold currents, and temperature characteristics are analyzed and good agreement is found with experimental results, including the temperature dependence of the threshold current and the prediction of a break-point temperature. The optimum design parameters are investigated for reduced threshold currents, and the effect of optical loss in the blocking regions on lateral-mode control is analyzed     

Millimetre-wave response of InGaAsP lasers

The intensity modulation response of 1.3 ?m-wavelength InGaAsP constricted-mesa lasers under pulsed operation is measured from 100 MHz to 40 GHz. 3 dB bandwidths of 25 GHz at 20°C and 31 GHz at ?40°C are observed.     

Short-cavity single-frequency InGaAsP buried-heterostructure lasers

Short-cavity (50?100 ?m) index-guided lasers made by recleaving conventional 1.3 ?m BH devices have been found to provide improved single-frequency output under both CW and modulated conditions.     

Etched-coupled-cavity InGaAsP/InP lasers

A new structure for coupled-cavity lasers operating at 1.25 ?m wavelength is presented. Using chemical etching, we made a three-cavity laser from an index-guided channelled-substrate Fabry-Perot laser. It oscillates in a single longitudinal mode with a side-mode suppression ratio of 200:1 in the pumping current range of 120 mA to 220 mA. The same mode was maintained at a fixed current of 160 mA as the heat-sink temperature was varied from 9°C to 45°C. The advantages of this laser over other coupled-cavity lasers are the simplicity of fabrication, the accuracy of cavity length control, and the possibility of incorporating short-etalon sections in the coupled cavities.     

InGaAsP/InP dual wavelength lasers

The first successful dual wavelength lasers emitting at 1.2 ?m and 1.3 ?m wavelengths are described. The lasers operated up to 0°C.     

High-speed InGaAsP/InP multiple-quantum-well laser

The authors describe practical high-speed InGaAsP/InP lasers based on compressively strained quantum wells. Buried heterostructure lasers with threshold currents of 10 mA and slope efficiencies of 0.23 mW/mA are used. A modulation bandwidth of 20 GHz is obtained at a low drive current of 90 mA. A K factor of 0.25 ns is obtained and the intrinsic bandwidth of these lasers is estimated at 35 GHz     

Reflection noise in index-guided InGaAsP lasers

We report a detailed study of the excess noise induced in index-guided InGaAsP laser structures by reflection feedback. The phenomena of high-frequency noise (1-5 GHz), low-frequency noise (< 100 MHz), and intensity fluctuations are shown to have a common physical origin in the unusual instability of the coupled laser-external cavity system. After a randomly occurring light intensity drop, the light output recovers in 10-15 steps, each corresponding to an external cavity roundtrip (high-frequency noise); the total recovery time corresponds to the low-frequency noise. The instability, and the subsequent noise, can be suppressed under conditions of very strong feedback such as obtained for lasers with anti-reflection-coated facets. The reflection noise characteristics are shown to be largely independent of the laser structure and structure modifications such as distributed feedback.     

Auger recombination rate in InGaAsP lasers

For the Auger recombination rate in InGaAsP there is an order of magnitude discrepancy between the measurements by Su et al. and the calculations by Dutta and Nelson, and Sugimura. It is suggested that a major source of this discrepancy is the method used to calculate the overlap integrals. A calculation that supports this suggestion is described.     

Extremely low-noise facet-reflectivity-controlled InGaAsP distributed-feedback lasers

Extremely low-noise (relative intensity noise (RIN) < - 160 dB/Hz) was attained with the facet-reflectivity-controlled 1.3-μm wavelength InGaAsP buried-heterostructure distributed-feedback lasers, Noise increase due to the optical feedback was greatly suppressed. It was interpreted as a result of counterbalanced mode competition between distributed-feedback mode and Fabry-Perot mode.     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved     

Low-threshold-current distributed-feedback InGaAsP/InP CW lasers

Distributed-feedback buried-heterostructure InGaAsP/InP lasers with room temperature CW threshold current as low as 50 mA, corresponding to a current density of 2.3 kA/cm2, are presented. CW operation in the temperature range from ?20°C to 58°C was confirmed.     

Intermodulation and harmonic distortion in InGaAsP lasers

A theoretical and experimental study is presented of intermodulation and harmonic distortion in high-speed 1.3 and 1.5 ?m InGaAsP lasers modulated at frequencies up to 8 GHz. It is found that all lasers measured, including Fabry-Perot and distributed feedback lasers, generate approximately the same distortion levels for a given modulation depth and relaxation resonance frequency. There are minor differences between lasers, which result from differences in the damping of the small-signal resonance peak.     

Dual wavelength InGaAsP/Inp TJS lasers

InGaAsP/InP dual wavelength TJS lasers emitting at 1.17 ?m and 1.3 ?m wavelengths at room temperature are described. The threshold currents for both diodes are the same. The fabrication procedure and characteristics of the lasers are presented.     

1.3 ?m InGaAsP DCPBH multiquantum-well lasers

We report the fabrication and performance characteristics of InGaAsP double-channel planar buried heterostructure (DCPBH) lasers with multiquantum-well active layers emitting at 1.3 ?m. These lasers have threshold currents in the range 40?50 mA at 30°C, external differential quantum efficiencies of ?50% at 30°C and T0 values ?160 to 180 K in the temperature range 10?60°C.     

Properties of wide-mesastripe InGaAsP/InP lasers

Wide-mesastripe InGaAsP/InP heterostructure lasers emitting at 1.3–1.5 µm were grown by metal-organic chemical vapor deposition (MOCVD). Radiation-power-current and spectral characteristics of the lasers have been studied in pulsed and continuous wave (cw) operation in the temperature range of 10–60°C. The temperature of the active region of the diode laser is higher by 30–60°C than that of the copper heatsink upon saturation of the cw output power. The temperature dependence of the differential quantum efficiency strongly affects the cw output power. Output powers of 3 and 2.6 W are achieved in mesastripe lasers in cw operation, and 9 and 6.5 W in pulsed operation, at wavelengths of 1.3 and 1.5 µm, respectively.     

Strained InGaAs/GaAs quantum well constricted-mesa lasers andapplication in a vertical-twin-guide tunable laser

Constricted-mesa semiconductor lasers containing a strained-layer InGaAs single-quantum-well-separate-confinement-heterostructure have been demonstrated. Very high etching selectivity between Al_xGa_1-xAs (x=0.9) and Al_xGa _1-xAs (x=<0.6) was achieved using diluted hydrofluoric acid to create a deeply undercut current confinement region, which enables a side contact for current injection. A process combining a self-aligned reactive ion etch and the undercut wet chemical etch has been developed for implementing a vertical twin-guide three-electrode tunable laser structure. Low-threshold currents for both single-guide devices with centered top contacts (5.2 mA) and twin-guide ones with side contacts (6.5 mA) were obtained     

Low threshold 1.55 ?m InGaAsP lasers double clad with InGaAsP confining layers

Preliminary results for 1.55 ?m InGaAsP double-heterostructure lasers with symmetrical InGaAsP confining layers are presented. The lowest broad-area threshold is 1.36 kA/cm2, which is 30% lower than the best value previously reported for 1.55 ?m lasers. This improvement is believed to be related to the absence of terracing on InGaAsP confining layers.     

Aging characteristics of InGaAsP/InP DFB lasers

Aging tests of InGaAsP/InP DFB lasers with a constant light output of 5 mW/facet and ambient temperatures 25°C and 40°C have been carried out. Up to the present, with an aging time of more than 2000 h for six lasers, appreciable degradations have been observed in their driving currents and spectra. This indicates that the corrugation grating near the active region has little influence on short-term reliability of DFB lasers.     

Temperature dependence of bistable InGaAsP/InP lasers

An increase of hysteresis current width in bistable lasers with two or three sections was observed at higher temperatures. A rate equation analysis was performed where both carrier density dependence on lifetime and the bleaching of saturable absorption by the spontaneous emission were taken into account. We show that the increased loss of injected carriers due to Auger recombination process causes the increase in the hysteresis width. A small-signal stability analysis for the switch-off point revealed that increased coupling between carriers in the gain and absorption regions, through the absorption of superradiant emission, has the effect of raising the switch-off point to higher current levels. It was shown experimentally that, without changing the temperature, the current hysteresis width can be controlled by adjusting the current distribution in three sections.     

High-frequency small-signal modulation characteristics of short-cavity InGaAsP lasers

Measured small-signal frequency-response characteristics of directly modulated long-cavity and short-cavity InGaAsP double-channel buried-heterostructure (DCBH) lasers are reported. Relaxation oscillation resonance frequencies as high as 9.4 GHz at a bias current of twice threshold have been obtained with short-cavity devices.