Optical modelling of a Si-based DBR laser source using a nanocrystal Si-sensitized Er-doped silica rib waveguide in the C-band

The availability of reliable silicon-based laser sources is at the basis of the integration of photonic and microelectronic devices on a single chip with consequent development of wavelength division multiplexing telecommunication systems. A high efficiency Si-based laser source with good stability at room temperature would encourage and push the large scale of integration of electronic and photonic devices within a single chip. Several techniques have been proposed for generating light with an internal quantum efficiency some order of magnitude greater than that typical of silicon (10-6) by using either electrical or optical pumping. Among them we mention the improvement of some fabrication process steps, reduction of the channels of non-radiative recombination, quantum confinement, the use of silicon nanocrystals (Si-ncs) incorporated in a silica matrix. This last technique is used in combination with Er3+ doping to generate light emission around 1500 nm in silicon, since Er-doped Si-ncs behave as electron-hole pairs trap, and the presence of Er shifts the emission peak to around 1500 nm. In this paper we have pointed out the optical model of a Si-based DBR laser including a Si-ncs Er-doped SiO2 rib waveguide, working at a wavelength in C-band. In particular, after a brief description of the structural and optical properties of the silicon crystals, we report on the model and design of the Er:Si-nc/SiO2 rib waveguide, of the optical cavity and of the Bragg mirrors. Numerical results are in good agreement with the literature

Design of a high-performance optical tweezer for nanoparticle trapping

Integrated optical nanotweezers offer a novel paradigm for optical trapping, as their ability to confine light at the nanoscale leads to extremely high gradient forces. To date, nanotweezers have been realized either as photonic crystal or as plasmonic nanocavities. Here, we propose a nanotweezer device based on a hybrid photonic/plasmonic cavity with the goal of achieving a very high quality factor-to-mode volume (Q/V) ratio. The structure includes a 1D photonic crystal dielectric cavity vertically coupled to a bowtie nanoantenna. A very high Q/V ~ 107 (λ/n)−3 with a resonance transmission T = 29 % at λR = 1381.1 nm has been calculated by 3D finite element method, affording strong light–matter interaction and making the hybrid cavity suitable for optical trapping. A maximum optical force F = −4.4 pN, high values of stability S = 30 and optical stiffness k = 90 pN/nm W have been obtained with an input power Pin = 1 mW, for a polystyrene nanoparticle with a diameter of 40 nm. This performance confirms the high efficiency of the optical nanotweezer and its potential for trapping living matter at the nanoscale, such as viruses, proteins and small bacteria

Solar Energy in Space Applications: Review and Technology Perspectives

Solar cells (SCs) are the most ubiquitous and reliable energy generation systems for aerospace applications. Nowadays, III-V multijunction solar cells (MJSCs) represent the standard commercial technology for powering spacecraft, thanks to their high-power conversion efficiency and certified reliability/stability while operating in orbit. Nevertheless, spacecraft companies are still using cheaper Si-based SCs to amortize the launching costs of satellites. Moreover, in recent years, new SCs technologies based on Cu(In,Ga)Se-2 (CIGS) and perovskite solar cells (PSCs) have emerged as promising candidates for aerospace power systems, because of their appealing properties such as lightweightness, flexibility, cost-effective manufacturing, and exceptional radiation resistance. In this review the current advancements and future challenges of SCs for aerospace applications are critically discussed. In particular, for each type of SC, a description of the device's architecture, a summary of its performance, and a quantitative assessment of the radiation resistance are presented. Finally, considering the high potential that 2D-materials (such as graphene, transition metal dichalcogenides, and transition metal carbides, nitrides, and carbonitrides) have in improving both performance and stability of SCs, a brief overview of some important results concerning the influence of radiation on both 2D materials-based devices and monolayer of 2D materials is also included

Recent advances in miniaturized optical gyroscopes

Low-cost chip-scale optoelectronic gyroscopes having a resolution ≤ 10 °/h and a good reliability also in harsh environments could have a strong impact on the medium/high performance gyro market, which is currently dominated by well-established bulk optical angular velocity sensors. The R&D activity aiming at the demonstration of those miniaturized sensors is crucial for aerospace/defense industry, and thus it is attracting an increasing research effort and notably funds.  In this paper the recent technological advances on the compact optoelectronic gyroscopes with low weight and high energy saving are reviewed. Attention is paid to both the so-called gyroscope-on-a-chip, which is a novel sensor, at the infantile stage, whose optical components are monolithically integrated on a single indium phosphide chip, and to a new ultra-high Q ring resonator for gyro applications with a configuration including a 1D photonic crystal in the resonant path. The emerging field of the gyros based on passive ring cavities, which have already shown performance comparable with that of optical fiber gyros, is also discussed

Theoretical investigation on the scale factor of a triple ring cavity to be used in frequency sensitive resonant gyroscopes

In this paper we study a multi-ring resonant structure including three evanescently coupled ring resonators (named triple ring resonator,TRR), with different ring radii and coupling coefficients, and coupled to two bus waveguides. The potential application of a TRR as a rotationsensor is analyzed and its advantages over a single ring resonator (SRR) under rotation conditions are also highlighted. When the coupledrings have different size and their inter-ring coupling coefficients are lower than the ring-bus coupling coefficients, the resonance frequencydifference between two counter-propagating beams induced by rotation is enhanced with respect to that of a single ring resonator (SRR)with the same footprint. The scale factor of the rotating TRR, which depends on the structural parameters (i.e. inter-ring and ring-buscoupling coefficients, lengths of the rings, overall propagation loss within the rings), is up to 1.88 times the value of the scale factor of aSRR, which depends only on the ring radius, by assuming that the waveguide structure in both configurations is the same. This promisingnumerical achievement results in a reduction of the sensor footprint of about two times, with respect to a single ring with the same scalefactor. The results obtained may be useful to define new configurations of frequency sensitive optical gyros in low-loss technology, havinga small volume. In fact, by properly choosing the structural parameters, the spectral response of the TRR is forced to assume a shape moresensitive to the resonant frequency shift due to the rotation with respect to that one of a SRR

Genetic aspects underlying the normocalcemic and hypercalcemic phenotypes of primary hyperparathyroidism

purpose: hypercalcemic primary hyperparathyroidism (PHPT) is a common endocrine disorder that has been very well characterized. In contrast, many aspects of normocalcemic primary hyperparathyroidism (NPHPT) such as natural history, organ damage, and management are still matter of debate. In addition, both the pathophysiology and molecular basis of NPHPT are unclear. we investigated whether PHPT and NPHPT patient cohorts share the same pattern of genetic variation in genes known to be involved in calcium and/or bone metabolism. Research design and methods: Genotyping for 9 single nucleotide polymorphisms (SNPs) was performed by Real-Time PCR (TaqMan assays) on 27 NPHPT and 31 PHPT patients evaluated in a tertiary referral center. the data of both groups were compared with 54 in house-controls and 503 subjects from the 1,000 genomes Project. All groups were compared for allele/haplotype frequencies, on a single locus, two loci and multi-locus basis. Results: The NPHPT group differed significantly at SNPs in OPG and ESR1. also, the NPHPT cohort was peculiar for pairwise associations of genotypes and for the overrepresentation of unusual multilocus genotypes. Conclusions: Our NPHPT patient set harboured a definitely larger quota of genetic diversity than the other samples. Specific genotypes may help in defining subgroups of NPHPT patients which deserve ad hoc clinical and follow-up studies

Highly preferential association of NonF508del CF mutations with the M470 allele

AbstractBackgroundOn the basis of previous findings on random individuals, we hypothesized a preferential association of CF causing mutations with the M allele of the M470V polymorphic site of the CFTR gene.MethodsWe have determined the M/V-CF mutation haplotype in a series of 201 North East Italian and 73 Czech CF patients who were not F508del homozygotes, as F508del was already known to be fully associated with the M allele.ResultsOut of 358 not F508del CF genes, 84 carried the V allele and 274 the less common M allele. In the N-E Italian population, MM subjects have a risk of carrying a CF causing mutation 6.9× greater than VV subjects when F508del is excluded and 15.4× when F508del is included. In the Czech population a similar, although less pronounced, association is observed.ConclusionsBesides the possible biological significance of this association, the possibility of exploiting it for a pilot screening program has been explored in a local North East Italian population for which CF patients were characterized for their CF mutation. General M470V genotyping followed by common CF mutation screening limited to couples in which each partner carries at least one M allele would need testing only 39% of the couples, which contribute 89% of the total risk, with a cost benefit

Volcanic Risk Management: the Case of Mt. Etna 2006 Eruption

Mt. Etna volcano is located in a very populated area of eastern Sicily (Italy). Its permanent degassing activity from summit craters and frequent eruptions impact significantly on town habitations and cultivated areas. In the latest years Etna has produced copious ash emission causing great losses to local economy and causing serious hazards to national and international air traffic over Mediterranean area and the often closure of Catania airport. In July 2006 eruptive vents opened on the East and South flanks of the summit craters showing irregular explosive and effusive activity lasting 6 months. This eruption represented the opportunity to perform the pre-operative test of FP6 Eurorisk-Preview (Prevention, Information and Early Warning) project aimed to develop tools for monitoring volcanoes. The test was performed during two temporal phases: the first one of early-warning was aimed to measure ground deformation and the second one during the crisis to survey volcanic ash produced during the explosions. The ground deformations were measured through the elaboration of SAR data. Beside the geophysical objectives, the test was also important to check data availability and efficiency of European Space Agency procedures. The pre-operative test has been peculiar to understand and quantify the delivering time of the final satellite products expected from the Volcanological Observatory in operative case. The analysis of July 2005 - July 2006 SAR data showed a pre-eruptive inflation trend in agreement with the ground network of GPS data. The magmatic source, that produced the September - October activity, has been located about 2.7 km below the summit craters. During the crisis phase characterized by paroxysmal activity, the Italian Civil Protection (DPC) in charge of airport closure in case of volcanic hazard, requested the satellite volcanic ash product retrieved from the NASA-MODIS data. An agreement between the industry Telespazio as direct broadcast of satellite data at Matera station and INGV was signed in order to elaborate the data in near-real time. The volcanic ash product provided information about: the presence of volcanic ash in the air; the affected area; the volcanic plume dispersal direction, dimensions and altitude and the volcanic ash loading. The satellite products and the observations report have been successively inserted in a web-interface. At the same time the observations report has been linked to the DPC dedicated Web-GIS interface that allows in a short time the availability of volcanic ash information to DPC in support to their decisions.Published77-811.10. TTC - Telerilevamentoope

A new approach for identifying non-pathogenic mutations. An analysis of the cystic fibrosis transmembrane regulator gene in normal individuals

Given q as the global frequency of the alleles causing a disease, any allele with a frequency higher than q minus the cumulative frequency of the previously known disease-causing mutations (threshold) cannot be the cause of that disease. This principle was applied to the analysis of cystic fibrosis transmembrane conductance regulator (CFTR) mutations in order to decide whether they are the cause of cystic fibrosis. A total of 191 DNA samples fl-om random individuals from Italy, France, and Spain were investigated by DGGE (denaturing gradient gel electrophoresis) analysis of all the coding and proximal non-coding regions of the gene. The mutations detected by DGGE were identified by sequencing. The sample size was sufficient to select essentially all mutations with a frequency of at least 0.01. A total of 46 mutations was detected, 20 of which were missense mutations. Four new mutations were identified: 1341+28 C/T, 2082 C/T, L1096R, and I1131V. Thirteen mutations (125 G/C, 875+40 A/G, TTGAn, IVS8-6 5T, IVS8-6 9T, 1525-61 A/G, M470V, 2693 T/G, 3061-65 C/A, 4002 A/G, 4521 G/A, IVS8 TG10, IVS8 TG12) were classified as non-CF-causing alleles on the basis of their frequency. The remaining mutations have a cumulative frequency far exceeding q; therefore, most of them cannot be CF-causing mutations. This is the first random survey capable of detecting all the polymorphisms of the coding sequence of a gene