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     

AlInGaAs/AlGaAs strained quantum-well ridge waveguide lasers grownby metalorganic chemical vapor deposition

AlInGaAs/AlGaAs strained quantum-well ridge waveguide diode lasers with an emission wavelength of 890 nm are presented. These devices exhibit both single spatial and longitudinal mode operation up to 30 mW of optical output power. A CW threshold current of 13 mA was obtained for a 5-μm-wide ridge waveguide having a cavity length of 500 μm. The differential quantum efficiency was 52%. The lateral and perpendicular far-field radiation patterns (FWHM) from the laser were 6° and 51°, respectively. Reliability testing on uncoated gain-guided lasers made from the same wafer showed no sudden death failures and degradation rates as low as 4.6%/kh     

InGaAs-GaAs-InGaP distributed feedback buried heterostructurestrained quantum-well lasers for high-power operation at 0.98 μm

Data are presented on device results from InGaAs-GaAs distributed feedback buried heterostructure (DFB BH) strained-quantum-well lasers with InGaP cladding layers. DFB BH lasers with a p-n InGaP current blocking junction entirely grown by a three-step MOVPE on GaAs substrates show a low laser threshold of 3.2 mA and a high output power of 41 mW with single-longitudinal-mode operation, both measured CW at RT. The monomode oscillation is obtained even at the injection current of 140 mA (44 times the laser threshold) with the side-mode suppression ratio of 35 dB and the temperature sensitivity of Bragg modes being 0.5 Å/°C measured between 20 and 40°C     

Low-threshold, high-temperature operation of 1.2 μm InGaAsvertical cavity lasers

The growth and characterisation of high performance InGaAs/GaAs quantum-well vertical cavity lasers with an emission wavelength of 1215 nm is reported. Continuous wave operation is demonstrated up to 105°C with a threshold current below 1 mA for T<80°C. For a 2.5 μm device the room temperature threshold current, output power and slope efficiency is 0.6 mA, 0.6 mW and 0.2 W/A, respectively     

InGaAsP (λ=1.3 μm) strip buried heterostructure lasersgrown by MOCVD

The authors describe InGaAsP-InP index guides strip buried heterostructure lasers (SBH) operating at 1.3 μm with a 1.1-μm guiding layer grown by a two-step atmospheric pressure metalorganic chemical vapor deposition (MOCVD) growth procedure. These lasers are compared with buried heterostructure lasers having similar guiding layers under the active layer but terminated at the edge of the active layer. SBH lasers with 0.15-μm-thick active layer strips, 5-μm wide, and guide layers varying from 0 to 0.7 μm have threshold currents increasing from 34 to 59 mA, and nearly constant differential external quantum efficiencies of 0.2 mW/mA. The threshold current increases more rapidly with temperature with increasing guide layer thickness, with T₀ decreasing from 70°C for lasers without a guide layer to 54.3°C for lasers without a guide layer to 54.3°C for lasers with 0.7-μm-thick guide layers. Output powers of up to 30 mW/facet have been obtained from 254-μm-long lasers and were found to be insensitive to guide layer thickness     

Low-threshold laterally oxidized GaInP-AlGaInP quantum-well laserdiodes

Low-threshold, high-efficiency edge-emitting visible AIGaInP-GaInP laser diodes using a buried AlAs native oxides for carrier and optical confinement are described. The lasers incorporate a thin AlAs layer in the upper cladding region, which when laterally wet oxidized, forms a narrow aperture. The lasers operate with room temperature, continuous-wave (CW) threshold currents of 11 mA with external differential quantum efficiency of 34% per facet for an uncoated 300-μm-long 3.5-μm-wide device. As-fabricated lasers exhibited modest performance under CW operation. Post-fabrication annealing was shown to dramatically improve the device characteristics     

High-power temperature-insensitive gain-offset InGaAs/GaAsvertical-cavity surface-emitting lasers

The authors have grown 997 nm vertical-cavity surface-emitting lasers with an offset between the wavelength of the cavity mode and the quantum well gain peak to improve high temperature operation, and with higher aluminum-content barriers around the active region to improve the carrier confinement. They fabricated lasers of 8-15 and 20-μm diameters. The 8-μm-diameter devices exhibited CW operation up to 140°C with little change in threshold current from 15°C to 100°C, and the 20-μm-diameter devices showed CW output power of 11 mW at 25°C without significant heat sinking     

Continuous operation of high-power (200 mW) strained-layerGa1-xInxAs/GaAs quantum-well lasers with emissionwavelengths 0.87⩽λ⩽0.95 μm

Separate confinement single-quantum-well lasers with 100-120 Å-thick strained Ga_1-xIn_xAs/GaAs active layers have been grown on (100) GaAs substrates by metalorganic chemical vapour deposition. Ten-stripe proton-implanted arrays with 90 μm-wide aperture and 250 μm cavity length emit 200 mW CW optical power at wavelengths 0.87⩽λ⩽0.95 μm. Lifetest data on an uncoated device emitting 90 mW/facet at 50°C and λ=0.95 μm suggest a mean-time-to-failure in excess of 2500 h at room temperature. The performance of lasers with strained Ga_1-xIn_xAs quantum wells is comparable to that of unstrained Al_xGa_1-xAs/GaAs quantum-well lasers without facet coating     

Single-mode distributed-feedback 761-nm GaAs-AlGaAs quantum-welllaser

We have developed single-mode distributed-feedback 761-nm GaAs-AlGaAs quantum well lasers as sources for O₂ sensing through laser absorption spectroscopy. Devices containing a 4-μm-wide ridge waveguide exhibit low threshold currents of 25 mA and quantum efficiencies greater than 35% at output powers in excess of 25 mW. The spectral linewidths of these devices are 12.0 MHz at 15 mW. Temperature- and current-tuning rates are 0.06 nm/°C and 0.0075 nm/mA (-3.9 GHz/mA), respectively. The devices display smooth, continuous, single-mode wavelength tuning over a 4.2 nm interval     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

分子束外延生长高应变单量子阱激光器

采用分子束外延方法研究了高应变InGaAs/GaAs量子阱的生长技术.将InGaAs/GaAs量子阱的室温光致发光波长拓展至1160nm,其光致发光峰半峰宽只有22meV.研制出1120nm室温连续工作的InGaAs/GaAs单量子阱激光器.对于100μm条宽和800μm腔长的激光器,最大线性输出功率达到200mW,斜率效率达到0.84mW/mA,最低阈值电流密度为450A/cm2,特征温度达到90K.     

Uniform linear arrays of strained-layer InGaAs-AlGaAs quantum-wellridge-waveguide diode lasers fabricated by ECR-IBAE

Uniform linear arrays of strained-layer multiple-quantum-well InGaAs-AlGaAs ridge-waveguide diode lasers have been fabricated that operate near 980 nm and have low threshold currents I_th and high differential quantum efficiencies η_d. Uniformity was achieved by a combination of uniform ion-beam-assisted etching with an electron cyclotron resonance ion source and uniform organometallic vapor-phase epitaxial (OMVPE) growth. We investigated the effects of device geometry, namely, ridge width, cavity length, and remaining cladding thickness outside the ridge t, on I_th and η_d. For uncoated lasers with 500-μm-long cavities, 2- to 3-μm-wide ridges, and t=165±75 nm fabricated in double-quantum-well OMVPE material, I_th was typically in the range 6-7 mA and η_d was >40% per facet. A 24-element array of 2-μm-wide, 200-μm-long ridge-waveguide lasers with a high reflection coating on the back facet exhibited excellent uniformity, with threshold currents and single-ended differential quantum efficiencies that averaged 3.4 mA and 72%, respectively. Similar arrays with high-reflectivity coatings on both facets exhibited threshold currents as low as 2 mA     

Temperature dependence of light-current characteristics of0.98-μm Al-free strained-quantum-well lasers

The decrease of the differential efficiency of 0.98-μm semiconductor lasers with temperature can make high power, high temperature applications difficult. We present an experimental and theoretical study of the temperature dependence of the internal quantum efficiency, internal loss and differential gain of 0.98-μm InGaAs/InGaAsP/InGaP strained quantum well lasers. In contrast to some earlier results, our measurements show the dominance of internal loss, attributed to free carrier absorption, in determining the temperature dependence of the differential efficiency, and show that leakage current is negligible below 120°C     

High-performance λ=1.3 μm InGaAsP-InP strained-layerquantum well lasers

Compressively and tensile strained InGaAsP-InP MQW Fabry-Perot and distributed feedback lasers emitting at 1.3-μm wavelength are reported. For both signs of the strain, improved device performance over bulk InGaAsP and lattice-matched InGaAsP-InP MQW lasers was observed. Tensile strained MQW lasers show TM polarized emission, and with one facet high reflectivity (HR) coated the threshold currents are 6.4 and 12 mA at 20 and 60°C, respectively. At 100°C, over 20-mW output power is obtained from 250-μm-cavity length lasers, and HR-coated lasers show minimum thresholds as low as 6.8 mA. Compressively strained InGaAsP-InP MQW lasers show improved differential efficiencies, CW threshold currents as low as 1.3 and 2.5 mA for HR-coated single- and multiple quantum well active layers, respectively, and record CW output powers as high as 380 mW for HR-AR coated devices. For both signs of the strain, strain-compensation applied by oppositely strained barrier and separate confinement layers, results in higher intensity, narrower-linewidth photoluminescence emissions, and reduced threshold currents. Furthermore, the strain compensation is shown to be effective for improving the reliability of strained MQW structures with the quantum wells grown near the critical thickness. Linewidth enhancement factors as low as 2 at the lasing wavelength were measured for both types of strain. Distributed feedback lasers employing either compressively or tensile strained InGaAsP-InP MQW active layers both emit single-mode output powers of over 80 mW and show narrow linewidths of 500 kHz     

1.3-μm CW lasing of InGaAs-GaAs quantum dots at room temperaturewith a threshold current of 8 mA

We demonstrate the first 1.3-μm continuous-wave (CW) lasing at room temperature of self-assembled InGaAs-GaAs quantum dots. High-density 1.3-μm emission dots were successfully formed by the combination of low-rate growth and InGaAs-layer overgrowth methods of molecular beam epitaxy. The 1.3-μm ground-level CW lasing occurred at up to 40°C, and the threshold current of 8 mA at 25°C is less than one thirtieth of values ever reported for 1.3-μm dot pulse lasers. The achievement represents a milestone for creating quantum-dot lasers applicable to fiber-optic communication system     

High-performance strain-compensated InGaAs-GaAsP-GaAs(λ=1.17 μm) quantum well diode lasers

This letter reports studies on highly strained and strain-compensated InGaAs quantum-well (QW) active diode lasers on GaAs substrates, fabricated by low-temperature (550°C) metal-organic chemical vapor deposition (MOCVD) growth. Strain compensation of the (compressively strained) InGaAs QW is investigated by using either InGaP (tensile-strained) cladding layer or GaAsP (tensile-strained) barrier layers. High-performance λ=1.165 μm laser emission is achieved from InGaAs-GaAsP strain-compensated QW laser structures, with threshold current densities of 65 A/cm² for 1500-μm-cavity devices and transparency current densities of 50 A/cm². The use of GaAsP-barrier layers are also shown to significantly improve the internal quantum efficiency of the highly strained InGaAs-active laser structure. As a result, external differential quantum efficiencies of 56% are achieved for 500-μm-cavity length diode lasers     

Stable operation (over 5000 h) of high-power 0.98-μm InGaAs-GaAsstrained quantum well ridge waveguide lasers for pumpingEr3+-doped fiber amplifiers

A maximum output power of 115 mW and a slope efficiency of 0.92 W/A have been achieved in 0.98-μm InGaAs strained quantum well lasers with a 3-μm-wide ridge waveguide structure for efficient fiber coupling. Stable operation of over 5000 h under 50°C constant power operation with an optical power density of 3.9 MW/cm² has been demonstrated with a degradation rate as low as 5×10^-6 per hour. These results show that this device is promising as a practical pumping source for Er³⁺-doped fiber optical amplifiers     

GaAs:GaAlAs ridge waveguide lasers and their monolithic integrationusing the ion beam etching process

The fabrication and performance characteristics of GaAs/GaAlAs ridge waveguide lasers are discussed. Threshold currents as low as 8 mA and differential quantum efficiencies as high as 90% were obtained for 250-μm-long graded-index separate-confinement heterostructure with single quantum well (GRINSCH SQW) lasers. High-speed short-cavity ridge waveguide lasers for which both the ridge stripe and one-mirror facet were formed by Ar-ion beam etching were achieved. The dependence of threshold current and lasing spectra on the cavity length were theoretically and experimentally investigated. This process was successfully used to integrate a laser diode monolithically with a photodiode or a field-effect transistor     

Optical and microwave performance of GaAs-AlGaAs and strained layerInGaAs-GaAs-AlGaAs graded index separate confinement heterostructuresingle quantum well lasers

GaAs-AlGaAs and strained layer In_0.3Ga_0.7As-GaAs-AlGaAs GRINSCH SQW lasers grown by molecular beam epitaxy are discussed. The strained-layers have threshold currents of 12 mA for 30-μm×400-μm devices (1000 A/cm²) and threshold current densities of 167 A/cm² for 150-μm×800-μm devices. The threshold currents of strained-layer InGaAs lasers are lower than those of GaAs for all dimensions tested with 20-μm-wide GaAs devices exhibiting threshold currents three times those of In_0.3Ga_0.7As devices. Microwave modulation of 10-μm×500-μm strained-layer lasers with simple mesa structures yields bandwidths of 6 GHz. For all dimensions tested, strained-layer InGaAs devices have greater bandwidths than GaAs devices. These measurements confirm theoretical predictions of the effects of valence band modification due to biaxially compressive strain     

Semiconductor pump laser technology

Recent progress in high-power semiconductor lasers for erbium-doped fiber amplifiers is described, focusing on 1.48-μm InGaAsP/InP lasers and 0.98-μm InGaAs/GaAs lasers. The experimental output powers exceed 200 mW (the maximum power was 325 mW) for 1.48-μm lasers, and simulation results indicate that over 400 mW could be obtained by optimizing parameters in strained-layer (SL) multiple-quantum-well (MQW) lasers. Stable operation over a few thousand hours under 100-mW power is demonstrated for liquid-phase-epitaxy-grown lasers, MQW lasers, and SL-MQW lasers grown by all-metal organic vapor-phase epitaxy (MOVPE). For 0.98-μm lasers, improvement in the fiber coupling efficiencies and long-term reliabilities are described. Their power coupled into a single-mode fiber has reached over 100 mW, with coupling efficiencies of approximately 40%. Although reliability seems to be one of the drawbacks compared with 1.48-μm lasers, stable operation for over 10,000 h at 50°C and 30 mW has been reported