The main real-coded genetic algorithm (RCGA) research effort has been spent on developing efficient crossover operators. This study presents a taxonomy for this operator that groups its instances in different categories according to the way they generate the genes of the offspring from the genes of the parents. The empirical study of representative crossovers of all the categories reveals concrete features that allow the crossover operator to have a positive influence on RCGA performance. They may be useful to design more effective crossover models.

Silicon nitride photonics is on the rise owing to the broadband nature of the material, allowing applications of biophotonics, tele/datacom, optical signal processing and sensing, from visible, through near to mid-infrared wavelengths. In this paper, a review of the state of the art of silicon nitride strip waveguide platforms is provided, alongside the experimental results on the development of a versatile 300 nm guiding film height silicon nitride platform.

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Intermediate band solar cells (IBSCs) fabricated to date from In(Ga)As/GaAs quantum dot arrays (QD-IBSC) exhibit a quantum efficiency (QE) that extends to below bandgap energies. However, the production of sub-bandgap photocurrent relies often on the thermal and/or tunneling escape of carriers from the QDs, which is incompatible with preservation of the output voltage. In this work, we test the effectiveness of introducing a thick GaAs spacer in addition to an InAlGaAs strain relief layer (SRL) over the QDs to reduce carrier escape. From an analysis of the QE at different temperatures, it is concluded that escape via tunneling can be completely blocked under short-circuit conditions, and that carriers confined in QDs with an InAlGaAs SRL exhibit a thermal escape activation energy over 100 meV larger than in the case of InAs QDs capped only with GaAs.

Strained semiconductor nanostructures can be used to make single-photon sources, detectors and photovoltaic devices, and could potentially be used to create quantum logic devices. The development of such applications requires techniques capable of nanoscale structural analysis, but the microscopy methods typically used to analyse these materials are destructive. NMR techniques can provide non-invasive structural analysis, but have been restricted to strain-free semiconductor nanostructures because of the significant strain-induced quadrupole broadening of the NMR spectra. Here, we show that optically detected NMR spectroscopy can be used to analyse individual strained quantum dots. Our approach uses continuous-wave broadband radiofrequency excitation with a specially designed spectral pattern and can probe individual strained nanostructures containing only 1 × 10(5) quadrupole nuclear spins. With this technique, we are able to measure the strain distribution and chemical composition of quantum dots in the volume occupied by the single confined electron. The approach could also be used to address problems in quantum information processing such as the precise control of nuclear spins in the presence of strong quadrupole effects.

Room temperature photoluminescence at 1.6μm is demonstrated from InGaAs quantum dots capped with an 8nm GaAsSb quantum well. Results obtained from various sample structures are compared, including samples capped with GaAs. The observed redshift in GaAsSb capped samples is attributed to a type II band alignment and to a beneficial modification of growth kinetics during capping due to the presence of Sb. The sample structure is discussed on the basis of transmission electron microscopy results.

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