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.<>     

Characterization of mass-transported p-substrate GaInAsP/InPburied-heterostructure lasers with analytical solutions for electricaland thermal resistances

Studies have been carried out to evaluate mass-transported p-substrate GaInAsP/InP buried-heterostructure lasers, which have a number of potential advantages over the more conventional n-substrate lasers. Devices have been fabricated with series resistances as low as 3 Ω, in good agreement with the p-substrate spreading resistance calculated using conformal mapping. A further development of this theory yields simple formulas of thermal resistances of heat generated both in the active region and in the p-InP. The presently fabricated p-substrate lasers also showed CW threshold currents as low as 4.5 mA, differential quantum efficiencies as high as 34% per facet, output powers as high as 33 mW per facet, and a maximum total electrical-to-optical power conversion efficiency of 36%     

Room-temperature CW operation of GaAs-AlGaAs diode lasers on silicon-on-insulator wafers

GaAs-AlGaAs diode lasers have been fabricated on silicon-on-insulator wafers for the first time. Gain-guided graded-index separate-confinement heterostructure single-quantum-well (GRINSCH-SQW) lasers operated CW at room temperature with threshold current as low as 43 mA, differential quantum efficiency as high as 54%, and output power of more than 60 mW/facet. One device operated CW for 75 min at an output power of 1 mW/facet.<>     

Scaling of GaAs/AlGaAs laser diodes for submilliampere threshold current

GaAs/AlGaAs lasers grown by a single-step MBE on grooved substrates have been used to investigate the scaling of lasers for very low threshold current. By tuning the facet reflectivity and the laser length, to keep the photon lifetime constant, it has been possible to scale down the threshold current to 0.65 mA without changing the external efficiency.<>     

High-temperature CW operation of planar buried-ridge structurelasers at λ=1.5 μm

GaInAsP/InP-PBRS lasers emitting at 1.5 μm have been fabricated by multiple liquid-phase epitaxy. Effective current confinement is achieved without current blocking layers. CW threshold current is as low as 9 mA at 25°C. Output powers per facet of up to 10 mW at 80°C and 3.5 mW at 100°C are obtained. The maximum operation temperature of 110°C is the highest value yet achieved with this type of laser at 1°5 μm     

具有线性GRIN结构GaAs/AlGaAs单量子阱激光器

采用ＭＯＣＶＤ 方法成功地研制了具有线性ＧＲＩＮ 结构ＧａＡｓ／ＡｌＧａＡｓ单量子阱激光器。该激光器的峰值波长为８１５～８２５ ｎｍ ,阈值电流为１３０ ｍ Ａ。工作电流在４８０ ｍ Ａ 时,单面连续输出光功率高达２００ ｍ Ｗ,且基本保持在单模工作状态。工作在９７０ ｍ Ａ 时,单面连续输出光功率为０．５ Ｗ。     

High efficiency InGaAs/GaAs single-quantum-well lasers usingsingle-step metalorganic chemical vapor deposition

Low-threshold-current single-quantum-well InGaAs/GaAs lasers are fabricated by metalorganic chemical vapor deposition on a nonplanar substrate. By taking advantage of the growth rate and doping differences on different crystal facets during the growth, a buried heterostructure laser with natural current blocking p-n-p-n junction is formed by a single growth step. Threshold currents as low as 1.0 mA under pulsed operation and 1.2 mA under continuous-wave operation are obtained for uncoated lasers at room-temperature. The lasers showed high external quantum efficiency (80%) and high T₀ (150 K). High reflection coated laser (95%/95%) have CW threshold current as low as 0.28 mA     

Very-low-threshold, highly efficient, and low-chirp 1.55-/spl mu/m complex-coupled DFB lasers with a current-blocking grating

Low-threshold current DFB lasers have been fabricated based on a complex-coupled structure with a current blocking grating. A threshold current as low as 5 mA was obtained, which enabled high temperature operation up to 105/spl deg/C. Asymmetric facet coatings were applied to obtain a high efficiency of 0.3 W/A. The strained InGaAsP MQW active region and the antiphase coupling has resulted in a low modulation chirping. By direct modulation of the device at 2.488 Gb/s and using optical amplifiers, we have demonstrated digital transmission over a 235 km-long standard single-mode fiber with a power penalty of 1.55 dB.     

Low operating currents of monolithically integrated 780 nm/650 nm-band self-sustained pulsating lasers with silicon nitride current blocking layers

The characteristics of monolithically integrated 780 nm/650 nm-band self-sustained pulsating (SSP) lasers with silicon nitride current blocking layers are reported. The record low operating current of 60 mA at 5 mW, 70/spl deg/C and a characteristic temperature of 90 K over 20 to 70/spl deg/C were obtained from the 650 nm-band SSP lasers. The attenuation factor of the visibility was observed to be as low as 0.3, which ensures SSP operations of the dual-mode lasers.     

In(Al)GaAs–AlGaAs Wafer Fused VCSELs Emitting at 2- μm Wavelength

We demonstrate 2-mum wavelength, wafer-fused In(Al)GaAs-InP-AlGaAs-GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting single-mode power of 0.5 mW at room temperature with a threshold current of 4 mA and sidemode suppression ratio of over 30 dB. These devices can be continuously tuned with current by 5 nm without mode hopping, with a tuning rate of 0.31 nm/mA. These features demonstrate the potential of these long wavelength VCSELs for gas sensing and other optical spectroscopy applications.     

GaInAsP/InP DH laser on semi-insulating InP substrate with terrace structure

GaInAsP/InP DH lasers for the 1.3 ?m region were fabricated through a single LPE process on semi-insulating InP substrates with a terrace structure. The threshold current of the mounted lasers was typically 65 mA under CW operation at room temperature. Light output of 450 mW per facet was achieved at a pulsed injection current of 4.2 A.     

Performance characteristics of buried facet quarter-wave shifted distributed feedback lasers

The performance characteristics of quarter-wave shifted GaInAsP distributed feedback lasers emitting near 1.3 mu m are described. The quarter-wave shifted grating is fabricated on a substrate using the double-exposure holographic technique. The low reflectivity required for this quarter-wave shifted DFB laser is obtained using buried facets at both ends of the laser. The lasers have threshold current of 30 mA, quantum efficiency of 0.18 mW/mA/facet, bandwidth of 11.5 GHz at 10 mW and 10 dB chirp width of 2.5 AA under 40 mA modulation current at 5 Gbit/s.<>     

Molecular beam epitaxy-grown separate confinement buried heterostructure PbEuSeTe-PbTe diode lasers

Separate confinement buried heterostructure (SCBH) tunable PbEuSeTe-PbTe diode lasers were fabricated by molecular beam epitaxy for the first time. Continuous wave (CW) operating temperature of 215 K was realized, which is the highest CW operating temperature ever reported for lead-chalcogenide diode lasers. Preliminary results show a significant improvement in threshold current and emission power. Exceptionally low threshold currents of 2.5 mA at 120 K, 76 mA at 180 K, and 252 mA at 200 K were measured. The temperature tuning range of the SCBH diode laser spans between 6.49 /spl mu/m at 20 K to 4.19 /spl mu/m at 215 K.     

CW performance of an InGaAs-GaAs-AlGaAs laterally-coupleddistributed feedback (LC-DFB) ridge laser diode

Single-mode distributed feedback (DFB) laser diodes typically require a two-step epitaxial growth or use of a corrugated substrate. We demonstrate InGaAs-GaAs-AlGaAs DFB lasers fabricated from a single epitaxial growth using lateral evanescent coupling of the optical field to a surface grating etched along the sides of the ridge. A CW threshold current of 25 mA and external quantum efficiency of 0.48 mW/mA per facet were measured for a 1 mm cavity length device with anti-reflection coated facets. Single-mode output powers as high as 11 mW per facet at 935 nm wavelength were attained. A coupling coefficient of at least 5.8 cm^-1 was calculated from the subthreshold spectrum taking into account the 2% residual facet reflectivity     

A submilliampere-threshold multiquantum-well AlGaAs laser withoutfacet coating using single-step MOCVD

An extremely low threshold current, of 0.88 mA under continuous wave (CW) operation was obtained for a three-quantum-well AlGaAs-GaAs laser without facet coating at room temperature. This laser was fabricated using only single-step metalorganic chemical vapor deposition (MOCVD) on a nonplanar GaAs substrate. The energy conversion efficiency from input electric power to light output power was 42% at 1 mW/facet, which is the highest value for all types of lasers. The laser beam shape was nearly round with an aspect ratio of 0.86     

MQW wavelength-tunable DBR lasers with monolithically integrated external cavity electroabsorption modulators with low-driving voltages fabricated by selective-area MOCVD

The design and operation of multiple-quantum-well (MQW) wavelength-tunable distributed Bragg reflector (DBR) InGaAs QW lasers with nonabsorbing gratings and monolithically integrated external cavity electroabsorption modulators fabricated by selective-area MOCVD are presented. Uncoated devices exhibit CW threshold currents as low as 10.5 mA with slope efficiencies of 0.21 W/A from the laser facet. Wavelength tuning of 7 nm is obtained by injection current heating of the DBR section. These devices also exhibit extinction ratios of 18 dB from the modulator facet at a low modulator bias of 1 V, when measured with a broad-area detector. When coupled to a singlemode fiber, these devices exhibited high extinction ratios of 40 dB at a modulator bias of 1.25 V.     

Study on high-temperature performances of 1.3-/spl mu/m InGaAsP-InP strained multiquantum-well buried-heterostructure lasers

Stripe-width and cavity length dependencies of high-temperature performances of 1.3-/spl mu/m InGaAsP-InP well-designed buried-heterostructure strained multiquantum-well (MQW) lasers were investigated. The threshold currents as low as 4.5/10.5 mA and slope efficiencies as high as 0.48/0.42 mW/mA at 25/spl deg/C/85/spl deg/C were obtained in the MQW lasers with 1.5-/spl mu/m width, 250-/spl mu/m length, and 0.3/0.85 facet reflectivity. With temperature increasing from 25/spl deg/C to 85/spl deg/C, the MQW lasers exhibited lower output power degradation, the minimum value was 1.78 dB at an operation current of 45 mA. The MQW lasers were suitable for application in optical access networks.     

Laterally Coupled DFB Lasers With Self-Aligned Metal Surface Grating by Holographic Lithography

A laterally coupled InGaAsP-InP distributed-feedback (DFB) laser operating around 1.55 mum was fabricated through a novel technique for the formation of metal surface gratings by holographic lithography. The self-aligned Cr DFB gratings were formed on the sidewalls as well as on both sides of the laser ridge by means of angled e-beam evaporation of Ti mask and metal-SiO₂ lift-off on the top of ridges. For an uncoated 3-mum-wide and 300-mum-long cavity, the device emitted an output power of ~9.7 mW/facet at an injection current of 100 mA with a threshold current of 29 mA and a slope efficiency of 0.14 mW/mA per facet at 20 degC under continuous-wave mode. A stable single-mode emission near 1.54 mum with a sidemode suppression ratio of nearly 28 dB was observed and a tuning coefficient of 0.21 nm/K was obtained in the temperature range of 15 degC -55 degC.     

High-performance 770-nm AlGaAs-GaAsP tensile-strained quantum-welllaser diodes

Experimental results on tensile-strained Al_0.3Ga_0.66As-GaAs_0.78P_0.22 separate-confinement-heterostructure single-quantum-well (SCH-SQW) laser diodes are reported. Threshold current density as low as 260 A/cm² for broad-stripe lasers with a cavity length of 1500 μm has been observed. Broad-stripe devices have operated cw at room temperature with output power as high as 620 mW/facet. Ridge-waveguide lasers have exhibited cw threshold currents as low as 13.5 mA and output power of 90 mW. The output of the tensile-strained lasers is TM polarized     

InGaAsSb(Gd)/InAsSbP double heterostructure lasers (λ=3.0–3.3 µm) for diode laser spectroscopy

Data on threshold currents, the differential quantum efficiency, the emission spectrum, current tuning, and radiation power of mesastripe InGaAsSb(Gd)/InAsSbP double heterostructure lasers with λ=3.0–3.3 µm and a cavity length of 70–150 µm in a temperature range of 50–107 K are reported. In the experiments, the threshold currents I _th<10 mA, a total output power of 0.5 mW/facet, and a single-mode power of 0.43 mW at 77 K in the cw regime were obtained. Lasers operated in the single-mode regime at currents I≤6I _th, the spectral purity was as high as 650: 1, the tuning rate was 210 cm^?1/A, and the tuning range was 10 cm^?1 wide. An example of methane detection at 3028.75 cm^?1 is presented.