Low-threshold and narrow-linewidth 1.5 mu m compressive-strained multiquantum-well distributed-feedback lasers

1.5 mu m compressive-strained multiquantum-well distributed-feedback lasers have been fabricated and characterised. 5.5 mA threshold current, 1 MHz mW linewidth-power product, and 600 kHz minimum linewidth were measured on 500 mu m long devices. Measured threshold current as low as 2.2 mA was also obtained on 150 mu m long devices. Both low threshold and narrow linewidth are attributed to the reduced transparency current and linewidth enhancement factor due to the effect of strain.<>     

1.5 mu m compressive-strained multiquantum-well 20-wavelength distributed-feedback laser arrays

The wide gain spectrum of compressive-strained multiquantum-well active layers was used to fabricate 20-wavelength distributed-feedback laser arrays. A record wide-wavelength span of 131 nm in the 1.5 mu m wavelength region was demonstrated. The maximum intrinsic modulation response, measured by a parasitic-free optical modulation technique, reaches 16 GHz.<>     

High performance DFB-MQW lasers at 1.5 mu m grown by GSMBE

1.5 mu m GaInAs multiquantum well distributed feedback lasers have been successfully fabricated on an InP grating substrate by GSMBE. DFB mode oscillation at high output power (50 mW) and narrow linewidth (1.3 MHz) have been obtained.<>     

Fabrication and performance characteristics of InGaAsP ridge-guide distributed-feedback multiquantum-well lasers

The fabrication and performance characteristics of InGaAsP ridge-guide distributed-feedback lasers with multiquantum-well active layers are reported. The lasers are 320 ?m long and have four active wells (?300 ? thick). The lasers have threshold current ?100 mA at 30°C, external differential quantum efficiency ?0.1 mW/mA/facet at 30°C and To? 60 K and can be operated in the same DFB mode up to 70°C. The measured frequency chirp is about a factor of 3 smaller than that for conventional double-heterostructure lasers. The smaller chirp should allow larger repeater spacing for high-bit-rate long-distance fibre transmission systems applications.     

Low-threshold 1.5 μm compressive-strained multiple- andsingle-quantum-well lasers

Design considerations for low-threshold 1.5-μm lasers using compressive-strained quantum wells are discussed. Parameters include transparency current density, maximum modal gain, bandgap wavelength, and carrier confinement. The optical confinement for a thin quantum well in the separate-confinement heterostructure (SCH) and the step graded-index separate-confinement heterostructure (GRINSCH) are analyzed and compared. 1.5-μm compressive-strained multiple- and single-quantum-well lasers have been fabricated and characterized. As a result of the compressive strain, the threshold current density is loss limited instead of transparency limited. By the use of the step graded-index separate-confinement heterostructure to reduce the waveguide loss, a low threshold current density of 319 A/cm² was measured on compressive-strained single-quantum-well broad-area lasers with a 27 μ oxide stripe width     

Continuous-wave operation of 1.5 ?m distributed-feedback ridge-waveguide lasers

CW operation of 1.5 ?m ridge-waveguide DFB lasers is reported for the first time. The ridge-waveguide DFB laser structure offers the prospect of high modulation speeds due to the absence of parasitic capacitances associated with reverse-biased current-blocking layers. These devices also represent the first report of CW operation of DFB lasers fabricated using the hybrid LPE/MOCVD crystal-growth technique and also of DFB lasers with gratings produced by electron-beam lithography.     

All-optical bistable switching dynamics in 1.55-μm two-segmentstrained multiquantum-well distributed-feedback lasers

All-optical bistable switching dynamics of 1.55-μm two-segment strained multiquantum-well (MQW) distributed-feedback (DFB) lasers were systematically studied both experimentally and theoretically. Some fundamental optical functionalities, including all-optical set-reset (flip-flop) operations, were demonstrated. The switching responses of these bistable lasers were studied, for the first time, with optical injection from a single-mode DFB laser, indicating that the switching dynamics based on gain quenching and absorption saturation are inherently different. A theoretical model including optical injection was developed to study these all-optical bistable switching characteristics in segmented bistable lasers. It was found that the nonuniform distribution of the photon density in the bistable laser cavity induced by optical injection was essential to perform the time-domain switching operations. Simulations showed a good agreement with experimental observations and indicated design improvements. Although the switching responses in the range of tens of picoseconds can be obtained with these bistable lasers, the maximum repetition frequency of the bistable systems would still be limited to the hundreds of megahertz due to the slow carrier recovery time (5 ns) of the lasers     

Cavity length dependence of K-limited bandwidth in 1.6 mu m compressive-strained quantum well lasers

The intrinsic small signal frequency response of 1.6 mu m compressive-strained quantum well lasers is measured at various cavity lengths. The highest 3 dB bandwidth reached is approximately 18 GHz. Cavity length dependence on the K factor is investigated. It was found that the optimal condition for obtaining the highest possible K-limited is the same as that for obtaining the highest relaxation oscillation frequency for a given optical power.<>     

High performance quantum dot lasers on GaAs substrates operating in 1.5 /spl mu/m range

Stacked InAs/InGaAs quantum dots are used as an active media of metamorphic InGaAs-InGaAlAs lasers grown on GaAs substrates by molecular beam epitaxy. High quantum efficiency (/spl eta//sub i/>60%) and low internal losses (/spl alpha/<3-4 cm/sup -1/) are realised. The transparency current density per single QD layer is estimated as /spl sim/70 A/cm/sup 2/ and the characteristic temperature is 60 K (20-85/spl deg/C). The emission wavelength exceeds 1.51 /spl mu/m at temperatures above 60/spl deg/C.     

1.55 mu m multiquantum-well lasers with record performance obtained by atmospheric pressure MOVPE using organometallic phosphorus precursor

The recently available precursor biphosphinoethane (BPE) was used, alongside with phosphine and with tertbutylphosphine (TBP), to grow advanced multiquantum-well (MQW) laser wafers with five quaternary, compressive strained wells. The lowest threshold current densities and the lowest optical losses were obtained with BPE. In particular, the lowest threshold current density, 328 A/cm/sup 2/, is a record among published values for lasers with five wells. In this comparison, the wafer grown with phosphine came a close second and that grown with TBP was third.<>     

Long wavelength GaInAsSb-AlGaAsSb distributed-feedback lasers emitting at 2.84 /spl mu/m

Room-temperature continuous-wave operation of a singlemode GaInAsSb/GaSb/AlGaAsSb distributed feedback (DFB) laser is presented at a record long emission wavelength for this material system of 2.843 /spl mu/m. The threshold current at 20/spl deg/C is 75 mA. Mode selection was realised by metal gratings laterally patterned to a ridge waveguide. By varying the grating period, DFB emission from 2.738 up to 2.843 /spl mu/m is obtained.     

Narrow-linewidth strained-layer 1.5 mu m multiquantum well distributed feedback lasers

The performance characteristics of narrow-linewidth strained-layer 1.5 mu m multi-quantum-well distributed feedback (MQW-DFB) lasers are presented. Measured linewidth as low as 3.5 MHz has been observed for one of the 250 mu m long devices at 14.4 mW output. Under 1.7 Gbit/s 1.0, 1.0, . . . pattern signal modulation, the lasers have 20 dB down full width chirp in the range of 5-6 AA for the off state at 0.8 I/sub th/. The chirp widths are about half of those of bulk-active DFB lasers. A 1.7 Gbit/s amplitude-shift-keying transmission experiment using one of the low-chirp lasers has been demonstrated. The transmission over 60 km of standard fibre only result in a 0.8 dB dispersion power penalty and has a receiver sensitivity of -36.2 dBm at BER=10/sup -9/.<>     

Low threshold 1.5 mu m tensile-strained single quantum well lasers

The authors have experimentally found that the threshold current density of 1.5 mu m tensile-strained single quantum well lasers decreases with increased tensile strain. A threshold current density as low as of 197 A/cm/sup 2/ is obtained with an In/sub 0.3/Ga/sub 0.7/As well. With semi-insulating current blocking layers and high reflection facet coatings, a threshold current as low as 2 mA is obtained from 150 mu m long lasers and a maximum CW operation temperature of 135 degrees C is achieved from 1 mm long lasers.<>     

Spontaneous emission efficiency of compressively strained 1.5 mu m MQW lasers

The spontaneous emission efficiency of 1.5 mu m compressively strained MQW lasers was found to be higher than that of comparable unstrained devices. The activation energy for Auger recombination was higher in the strained devices. Both effects were explained in terms of a reduction in the hole mass by strain.<>     

1.55 mu m gain-coupled quantum-well distributed feedback lasers with high single-mode yield and narrow linewidth

The fabrication and characteristics of gain-coupled 1.55- mu m GaInAlAs quantum-well metal-clad ridge-waveguide distributed-feedback lasers are discussed. The gain-coupling mechanism was provided by a thin ternary loss grating layer with an estimated gain-coupling strength of about 30/cm. For as-cleaved devices, the single-mode yield was as high as 70 and 95% for 600- and 800- mu m-long devices, respectively. Typical threshold currents were 40 and 55 mA, respectively. Both the high single-mode yield and the pronounced asymmetric spectra were calculated theoretically and give a strong indication that a significant amount of gain coupling was realized in the laser structure. For a 600- mu m-long device, a continuous-wave (CW) output power of 10 mW and a minimum linewidth of 1.6 MHz were measured.<>     

1.55 mu m index/gain coupled DFB lasers with strained layer multiquantum-well active grating

The fabrication and characterisation results of a novel 1.55 mu m index/gain coupled DFB laser with a strained-layer multiquantum-well active grating are reported. The laser exhibits very clear spectral features due to gain-coupling effects.<>     

2.0-/spl mu/m single-mode operation of InGaAs-InGaAsP distributed-feedback buried-heterostructure quantum-well lasers

Distributed-feedback (DFB) buried-heterostructure (BH) lasers with quantum-well active region emitting at 2.0 /spl mu/m have been fabricated and characterized. The lasers with four wells showed performance of practical use: threshold current as low as 15 mA for 600-/spl mu/m-long devices and CW single-mode output up to 5 mW at 2.03 /spl mu/m under operation current of 100 mA were observed. The current- and temperature-tuning rates of DFB mode wavelength are 0.004 nm/mA and 0.125 nm/K, respectively.     

High temperature operation of lambda =1.5 mu m tensile strained multiple quantum well SIPBH lasers

The high temperature operation of 1.5 mu m wavelength, strained-layer multiple quantum well, semi-insulating planar buried heterostructure lasers is reported. The lasers, which are grown by low-pressure organometallic vapour phase epitaxy and which have four 1.6% tensile strained In/sub 0.3/Ga/sub 0.7/As wells (thickness 8 nm), operate in CW mode up to heatsink temperatures of 140 degrees C. The CW output power at 100 degrees C is 26 mW per facet. These results are a marked improvement when compared to data reported thus far for 1.5 mu m wavelength lasers.<>     

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.     

High performance 1.28 /spl mu/m GaInNAs double quantum well lasers

The use of multiple quantum wells and GaAs barriers favours the temperature stability and modulation bandwidth of GaInNAs lasers. It is shown that a very low threshold current density and a high characteristic temperature can be achieved for GaInNAs/GaAs double quantum well lasers, emitting at 1.28 /spl mu/m, when grown by molecular beam epitaxy under favourable conditions.