The Ga(AsBi) material system opens opportunities in the field of high efficiency infrared laser diodes. We report on the growth, structural investigations, and lasing properties of dilute bismide Ga(AsBi)/(AlGa)As single quantum well lasers with 2.2% Bi grown by metal organic vapor phase epitaxy on GaAs (001) substrates. Electrically injected laser operation at room temperature is achieved with a threshold current density of 1.56 kA/cm2 at an emission wavelength of ∼947 nm. These results from broad area devices show great promise for developing efficient IR laser diodes based on this emerging materials system.

The radiative and nonradiative components of the threshold current in 1.3 m, p-doped and undoped quantum-dot semiconductor lasers were studied between 20 and 370 K. The complex behavior can be explained by simply assuming that the radiative recombination and nonradiative Auger recombination rates are strongly modified by thermal redistribution of carriers between the dots. The large differences between the devices arise due to the trapped holes in the p-doped devices. These both greatly increase Auger recombination involving hole excitation at low temperatures and decrease electron thermal escape due to their Coulombic attraction. The model explains the high T 0 values observed near room temperature.

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InAs quantum-dot (QD) lasers were investigated in the temperature range 20-300 K and under hydrostatic pressure in the range of 0-12 kbar at room temperature. The results indicate that Auger recombination is very important in 1.3-m QD lasers at room temperature and it is, therefore, the possible cause of the relatively low characteristic temperature observed, of 0 = 41 K. In the 980-nm QD lasers where 0 = 110-130 K, radiative recombination dominates. The laser emission photon energy las increases linearly with pressure at 10.1 and 8.3 meV/kbar for 980 nm and 1.3m QD lasers, respectively. For the 980-nm QD lasers the threshold current increases with pressure at a rate proportional to the square of the photon energy 2 las . However, the threshold current of the 1.3m QD laser decreases by 26% over a 12-kbar pressure range. This demonstrates the presence of a nonradiative recombination contribution to the threshold current, which decreases with increasing pressure. The authors show that this nonradiative contribution is Auger recombination. The results are discussed in the framework of a theoretical model based on the electronic structure and radiative recombination calculations carried out using an 8 8 k p Hamiltonian.

In this work we study the nature of the band gap in GeSn alloys for use in silicon-based lasers. Special attention is paid to Sn-induced band mixing effects. We demonstrate from both experiment and ab-initio theory that the (direct) Γ-character of the GeSn band gap changes continuously with alloy composition and has significant Γ-character even at low (6%) Sn concentrations. The evolution of the Γ-character is due to Sn-induced conduction band mixing effects, in contrast to the sharp indirect-to-direct band gap transition obtained in conventional alloys such as Al1−xGaxAs. Understanding the band mixing effects is critical not only from a fundamental and basic properties viewpoint but also for designing photonic devices with enhanced capabilities utilizing GeSn and related material systems.

Electrically pumped GaAsBi/GaAs quantum well lasers are a promising new class of near-infrared devices where, by use of the unusual band structure properties of GaAsBi alloys, it is possible to suppress the dominant energy-consuming Auger recombination and inter-valence band absorption loss mechanisms, which greatly impact upon the device performance. Suppression of these loss mechanisms promises to lead to highly efficient, uncooled operation of telecommunications lasers, making GaAsBi system a strong candidate for the development of next-generation semiconductor lasers. In this report we present the first experimentally measured optical gain, absorption and spontaneous emission spectra for GaAsBi-based quantum well laser structures. We determine internal optical losses of 10–15 cm−1 and a peak modal gain of 24 cm−1, corresponding to a material gain of approximately 1500 cm−1 at a current density of 2 kA cm−2. To complement the experimental studies, a theoretical analysis of the spontaneous emission and optical gain spectra is presented, using a model based upon a 12-band k.p Hamiltonian for GaAsBi alloys. The results of our theoretical calculations are in excellent quantitative agreement with the experimental data, and together provide a powerful predictive capability for use in the design and optimisation of high efficiency lasers in the infrared.

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The manufacturing industry is regarded as one of the most demanding verticals with respect to URLLC requirements. A Device-to-Device (D2D) communication system is a key enabler that has been introduced to support URLLC. To enhance spectrum utilisation, D2D links can share access of radio spectrum resources occupied by cellular users. Spectrum reuse may result in performance degradation due to mutual co-channel interference of co-existing cellular and D2D users. Resource sharing in a D2D-based cellular network for wireless industrial applications is investigated in this paper. The presented schemes aim to maximise the overall system throughput while maintaining the Quality of Service / Experience (QoS/ QoE) requirements. Interference is managed by jointly considering admission and power control based on the relative distance between devices. A priced-Deferred Acceptance (p-DA) scheme with an incentive-based stability is developed to match D2D users to cellular resources. Numerical simulations show that the p-DA scheme is able to achieve better performance than the conventional DA algorithm and is close in performance to the presented centralised optimisation approach.