Broad-band superluminescent light-emitting diodes incorporating quantum dots in compositionally modulated quantum wells

We propose and demonstrate a technique for tailoring the emission bandwidth of /spl sim/1.3 /spl mu/m quantum dot superluminescent light-emitting diodes. A broadening of the emission is achieved by incorporating the InAs quantum dot layers in InGaAs quantum wells of different indium compositions. These structures exhibit a broader and flatter emission compared to a simple dot-in well structure comprised of wells of identical indium composition.     

Low-threshold-current-density 1.5 μm lasers using compressivelystrained InGaAsP quantum wells

A low-threshold current density (J_th) of 140 A/cm² for broad-area 1.5-μm semiconductor lasers with uncoated facets is demonstrated at a cavity length of 3.5 mm. This was achieved by the use of a single InGaAsP quantum well (QW) of 1.8% compressive strain inside a step-graded InGaAsP waveguide region. Low-cavity losses of 3.5 cm^-1 and a relatively wide quantum well as compared to InGaAs wells of equivalent strain contribute to this high performance. Double QW devices of 2 mm length showed threshold current densities of 241 A/cm². Quaternary single and double QWs of similar width but only 0. 9% strain gave slightly higher threshold current density values, but allowed growth of a 4 QW structure with a J_th of 324 A/cm² at L=1.5 mm     

High-efficiency light-emitting diodes at ≈1.3 μm usingInAs-InGaAs quantum dots

Light-emitting diodes (LEDs) based on long-wavelength, self-assembled InAs-InGaAs quantum dots (QDs) are demonstrated and characterized. The LEDs consist of a single layer of QDs positioned at λ/2 from a top gold mirror to enhance the extraction efficiency. The external quantum efficiency at room temperature is 1%, which corresponds to an estimated 13% radiative efficiency. High-injection electroluminescence and photovoltage spectra under reverse bias allow us to determine the transition energies of excited states in the QDs and bidimensional states in the adjacent InGaAs quantum well     

1.3 μm InGaAs/GaAs strained quantum well lasers with InGaPcladding layer

Using MOVPE, we fabricated strained quantum well 1.3 μm lasers with an InGaP cladding layer on a GaAs substrate. The lasers had a high gain coefficient of 60 cm^-1. Lasers with high reflection facets had a low threshold current density of 500 A/cm², and a high characteristic temperature of 100 K     

Electroabsorption properties of InGaAs/InAlAs multiple quantum wellstructures at 1.5 μm

The electroabsorption properties of InGaAs/InAlAs MQW structures are characterised in terms of Δα, Δα/F and Δα/α₀, where Δα is the electroabsorption, α₀ is the residual absorption coefficient under zero bias, and F is the applied electric field. The limitations of these structures for 1.5 μm modulators are primarily due to the relatively small Δα/F values as a result of the small well width. The results are compared with the literature     

High-power single-mode 2.0 μm laser diodes

Data are presented on high-power single-mode index-guided laser diodes fabricated from a strained-layer InGaAs-InGaAsP double quantum well heterostructure epitaxial design. The total maximum power and external efficiency achieved are 50 mW and 43%, respectively. The far-field is measured to be 31° by 46° in the parallel and perpendicular directions, yielding an aspect ratio of 1.5 for the single-mode laser diode. The optical output of the laser diode is a multi-longitudinal mode spectrum spanning 1.98-2.00 μm at an output power of 50 mW CW. The characteristic temperature of the laser diode is 48 K     

High-power 2.0 μm InGaAsP laser diodes

Data detailing the performance of strained-layer InGaAs/InGaAsP double-quantum-well laser diodes operating at 2.0 μm are presented. The total external efficiency and maximum power achieved are 55% and 1.6-W continuous wave (CW), respectively, from a 200-μm gain-guided laser diode. Measurements on gain-guided broad area devices yield an internal efficiency of 0.73 with a distributed loss coefficient, α, of 7.5 cm^-1. The measured threshold current density is 300 A/cm² for a 2-mm-long broad area device operated CW at 25°C     

Electroabsorption modulation in strained piezoelectric InGaAs/InPmultiquantum wells operating at λ≈1.55 μm

An investigation of absorption modulation using strained piezoelectric InGaAs/InP multiquantum wells grown on (111)B InP substrates is presented. Strong excitonic features are observed in the room temperature photocurrent spectra for a structure with 50 Å quantum wells under 0.6% compressive strain. The application of a reverse bias results in a large blue-shift of the absorption edge of up to 8 nm/V     

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     

A new GaAsP—InGaAs strained-layer super-lattice light-emitting diode

The GaAs1 - yPy-InxGa1 - xAS superlattice (SL) system with y = 2x has an average lattice constant equal to that of GaAs, thus allowing the fabrication of lattice-matched strained-layer double heterostructures. This new system can provide a large conduction band-edge discontinuity and higher electron mobility than the AlGaAs-GaAs system. The strained layers and subsequent GaAs layers epitaxially grown on them were found to be of high quality. Light-emitting diodes (LED's), based on this new superlattice, have been fabricated with emission in the wavelength range 0.9-1.1 µm. These LED's have operated for 200 h without any degradation in the output emission intensity. Also a dual-wavelength three-terminal device LED emitting near 0.87 and 0.9 µm has been fabricated. This is one of the first demonstrations of the potential applications of strained-layer superlattices (SLS).     

Multiple-quantum-well GaInNAs-GaNAs ridge-waveguide laser diodesoperating out to 1.4 μm

In this letter, results from a ridge waveguide laser diode (LD) structure, with three GaInNAs quantum wells (QWs) and GaNAs barriers, are presented. The sample was grown by solid source molecular beam epitaxy with an RF plasma nitrogen source. These devices differ from previously reported GaInNAs QWs LDs that used GaAs as the barrier material. The introduction of nitrogen into the barriers reduces the spectral blue shift caused by post-growth annealing. Long wavelength emission out to 1.405 μm was observed. The devices exhibited threshold current densities as low as 1.5 kA/cm², high differential efficiency of 0.67 W/A, and a maximum output power of 350 mW     

Broad-band emission from a multiple asymmetric quantum-well light-emitting diode

The authors demonstrate broadband light-emitting diode (LED) emission, with a full-width-at-half-maximum (FWHM) values >100 nm, based on concurrent multiple-state transitions in a single active layer containing two asymmetric quantum wells in the GaAs/AlGaAs material system. This spectral width is much broader (by a factor of 2.5) than that for commercial edge-emitting LEDs in the GaAs/AlGaAs system. The LED device is well suited for broadband source applications in wavelength-multiplexing-based, fibre-optic sensor network systems.<>     

High-speed performance of OMCVD grown InAlAs/InGaAs MSMphotodetectors at 1.5 μm and 1.3 μm wavelengths

A report is presented on the fabrication of high-speed In_0.53 Ga_0.47As metal-semiconductor-metal (MSM) photodetectors incorporating a high-quality lattice-matched InAlAs barrier enhancement layer, grown by organometallic chemical vapor deposition (OMCVD). Fast responses of ~55 ps full-width half-maximum at 1.5 μm and ~48 ps at 1.3 μm wavelengths are observed, corresponding to intrinsic device bandwidths of ~8 GHz and ~11 GHz, respectively. The absence of any tail to the pulse response, and of any low-bias DC gain, indicates a low-trap density at the InAlAs/InGaAs heterointerface. Bias independent dark currents of 10-20 μA are observed below breakdown, which occurred at >30 V in devices with a 500-A-thick InAlAs layer     

InGaAs-InGaAsP buried heterostructure lasers operating at 2.0 μm

Buried heterostructure lasers with highly strained InGaAs-InGaAsP active regions, emitting at 2 μm have been fabricated and tested. The lasers exhibited threshold current densities of 500 A/cm² for 1-mm-long cavities, an internal loss of 11 cm^-1, and characteristic temperatures as high as 50°C. The gain characteristics were also investigated and a linewidth enhancement factor of 8 was determined     

High-power GaInAsSb-AlGaAsSb multiple-quantum-well diode lasersemitting at 1.9 μm

High-power diode lasers emitting at ~1.9 μm have been fabricated from a quantum-well heterostructure having an active region consisting of five GaInAsSb wells and six AlGaAsSb barriers. For devices 300 μm wide and 1000 μm long, single-ended output power as high as 1.3 W cw has been obtained with an initial differential quantum efficiency of 47%. The pulsed threshold current density is as low as 143 A/cm² for 2000-μm-long devices     

Dark-line-resistant, aluminum-free diode laser at 0.8 μm

Quantum-well, lattice-matched InGaAsP lasers emitting at 0.8 μm are shown to exhibit resistance to 〈100〉 dark-line growth. This property in conjunction with the aluminum-free device structure augurs well for future high-power diodes and arrays operating near this wavelength     

Tunable laser-diode-pumped Nd:YAG microcrystal lasers at 1.4 μm

TEM₀₀ laser operation of a monolithic Nd:YAG crystal laser has been achieved on three transitions at 1.414 μm, 1.444 μm and at 1.431 μm with laser diode pumping at 808 nm. The laser threshold was 1.5 W and the maximum output power 50 mW. The gain linewidths at 1.414 μm and 1.444 μm were determined by means of temperature tuning the microcrystal lasers. Calculations for designing tunable single frequency microcrystal lasers have been performed     

Miniature Mach-Zehnder InGaAsP quantum well waveguideinterferometers for 1.3 μm

Electrooptic Mach-Zehnder interferometers with active lengths as small as 350 μm are discussed. These strip-loaded waveguide devices utilize the electrooptic effect in InGaAsP/InP quantum wells to achieve pi phase shift with single arm drive voltages of 12 V and 6 V drive in push-pull operation     

High-power highly strained InGaAs quantum-well lasers operating at1.2 μm

High-power highly strained In_xGa_1-xAs quantum-well lasers operating at 1.2 μm are demonstrated. The edge emitting broad area (BA) laser diode structures are grown by metal organic vapor phase epitaxy at low growth temperatures using trimethylgallium, trimethylindium, and arsine sources. In the laser structure, an InGaAs QW is sandwiched between the GaAs waveguide and AlGaAs cladding layers. The operating wavelength for the laser diode at room temperature (20°C) is about 1206 nm, which redshifts to 1219 nm at 46°C. The transparency current density for the BA laser diodes is as low as 52 A/cm² and the characteristic temperature value is 76 K. High-power laser operation in the pulse mode (about 1.6 W) at room temperature was achieved     

Strained-layer multiple-quantum-well InGaAs/GaAs waveguidemodulators operating around 1 μm

Detailed experimental results on the properties of multiple-quantum-well waveguide modulators on strained InGaAs/GaAs layers are presented. Transmission and photocurrent measurements are performed using a tunable Ti-sapphire-laser. The spectra reveal an absorption edge shift as large as 60 nm at 5 V reverse bias. Optimum performance is achieved around a wavelength of 1 μm, where an extinction ratio of up to 20 dB is obtained with an absorption loss of less than 2 dB/cm. The overall insertion loss of the modulator approaches a constant value of 6.5 dB at higher wavelengths (λ⩾980 nm) which is shown to be mainly affected by coupling losses