Theory of near infra-red germanium lasers

Due to major advances in silicon photonics technology and the importance of having a silicon-compatible laser operating in the 1.3 - 1.55 micron communications wavelength window. There is currently an intense interest in the optical properties of germanium, which has a direct band gap transition in this wavelength range. The Ge band structure can be engineered using biaxial or uniaxial strain in order to achieve optical gain. Recently, both optically pumped and electrical injection pumped lasing have been reported in Ge-on-Si devices. This work aims to perform gain modeling in a germanium laser grown on a silicon substrate which operates in the near infrared wavelength communications band. A description of the background theory of the variation of the relevant electronic band structure properties of Ge with the applied strain is given. Shifts of the conduction and valence band edges with strain (biaxial and uniaxial) applied to Ge grown on substrates of different orientations has been investigated using the linear deformation potential and k.p methods. In order to make Ge behave as a direct band gap material, and to have a good electron injection efficiency, an investigation of the combination of the applied strain and doping density on direct band gap and injected carrier efficiency were carried out at 0 K, for both bulk Ge and Ge quantum wells. At finite temperatures, the k.p method and effective mass approximation were used to calculate the energy bands for [001] bulk Ge, the quasi-Fermi levels for given values of carrier densities, and then the interband gain and IVBA were calculated for biaxially tensile strained [001] bulk Ge. Furthermore, a detailed description of the free carrier absorption coefficient calculation, accounting for both intervalley and intravalley scattering in strained [001] Ge is given. The effect of unequal electron and hole densities, which are required to achieve the interband gain and reduce the absorption coefficient due to IVBA and FCA in order to obtain the net gain, has been investigated for strained bulk n+ Ge at room and typical device temperatures

Green-Synthesized Graphene for Supercapacitors—Modern Perspectives

Graphene is a unique nanocarbon nanostructure, which has been frequently used to form nanocomposites. Green-synthesized graphene has been focused due to environmentally friendly requirements in recent technological sectors. A very important application of green-synthesized graphene-based nanocomposite has been observed in energy storage devices. This state-of-the-art review highlights design, features, and advanced functions of polymer/green-synthesized graphene nanocomposites and their utility in supercapacitor components. Green graphene-derived nanocomposites brought about numerous revolutions in high-performance supercapacitors. The structural diversity of conjugated polymer and green graphene-based nanocomposites has facilitated the charge transportation/storage capacity, specific capacitance, capacitance retention, cyclability, and durability of supercapacitor electrodes. Moreover, the green method, graphene functionality, dispersion, and matrix–nanofiller interactions have affected supercapacitance properties and performance. Future research on innovative polymer and green graphene-derived nanocomposites may overcome design/performance-related challenging factors for technical usages

The Association between Body Dysmorphic Disorder (BDD) and Acceptance of Cosmetic Surgery Scale (ACSS): A nationwide study from 25 medical schools

Background: Body dysmorphic disorder (BDD) is a psychological condition that is characterized by obsessive thinking about a perceived flaw in one's appearance that may eventually cause significant distress and impairment in life.Methods: A cross-sectional study was conducted between January 2021 and August 2021 using a previously validated and published questionnaires — The Body Image Disturbance Questionnaire (BIDQ) and Acceptance of Cosmetic Surgery Scale (ACSS).  Distributed to all medical students from 25 universities across all regions of Saudi Arabia. Results: A total of 1,776 respondents completed the questionnaire. Females represented 57.1% of the study population.More than half of the respondents were concerned and preoccupied with their body appearance (59.4% and 52.8%, respectively). The average of the BIDQ and ACSS scores was significantly higher in females compared to males, while higher socioeconomic status and higher educational level were also significantly related with higher BIDQ and ACSS scores. Furthermore, a higher BIDQ score was associated with higher scores on the ACSS

Enhanced light emission from improved homogeneity in biaxially suspended Germanium membranes from curvature optimization

A silicon compatible light source is crucial to develop a fully monolithic silicon photonics platform. Strain engineering in suspended Germanium membranes has offered a potential route for such a light source. However, biaxial structures have suffered from poor optical properties due to unfavorable strain distributions. Using a novel geometric approach and finite element modelling (FEM) structures with improved strain homogeneity were designed and fabricated. Micro-Raman (μ-Raman) spectroscopy was used to determine central strain values. Micro-photoluminescence (μ-PL) was used to study the effects of the strain profiles on light emission; we report a PL enhancement of up to 3x by optimizing curvature at a strain value of 0.5% biaxial strain. This geometric approach offers opportunity for enhancing the light emission in Germanium towards developing a practical on chip light source

Detection of kidney complications relevant concentrations of ammonia gas using plasmonic biosensors : A review

Kidney-related health problems cause millions of deaths around the world annually. Fortunately, most kidney problems are curable if detected at the earliest stage. Continuous monitoring of ammonia from exhaled breath is considered as a replacement for the conventional blood-based monitoring of chronic kidney disease (CKD) and kidney failure owing to its cost effectiveness, non-invasiveness, excellent sensitivity, and capabilities for real-time measurement. The detection of ammonia for renal failure requires a biosensor with a detection limit of 1000 ppb (1 ppm). Among biosensors, plasmonic biosensors have attracted considerable research interest due to their potential for ultra-sensitivity, single particle/molecular level detection capability, multiplexing capability, photostability, real-time measurement, label-free measurement, room temperature operation, naked-eye readability, ease of miniaturization via simple sensor chip fabrication, and instrumentation, among other features. In this review, plasmonic sensors for the detection of ammonia gas relevant to kidney problems (LOD ≤ 1 ppm) are reviewed. In addition, the utilized strategies and surface functionalization for the plasmonic sensor are highlighted. Moreover, the main limitations of the reported sensors are stated for the benefit of future researchers. Finally, the challenges and prospects of plasmonic-based ammonia gas biosensors for potential application in the monitoring and screening of renal (kidney) failure, as well as the endpoint of the dialysis session, are stated

Spectral Characteristics and Molecular Structure of (E)-1-(4-Chlorophenyl)-3-(4-(Dimethylamino)Phenyl)Prop-2-en-1-One (DAP)

In this work, a laser dye of (E)-1-(4-chlorophenyl)-3-(4-(dimethylamino)phenyl)prop-2-en-1-one (DAP) was synthesized and examined as a new laser medium. The compound DAP’s photophysical properties were investigated under the influence of solvents, concentrations, and pump power excitations. The absorption spectra showed a single band, and the shape of the spectra remained the same, regardless of the optical density. The fluorescence spectra showed a band around 538 nm; its intensity was inversely proportional to the concentration. DAP exhibits dual amplified spontaneous emission (ASE) bands at 545 and 565 nm under suitable pump power laser excitation and concentration. The results revealed that the ASE band at 565 nm is affected by solvents polarity, concentrations and pump power energies. This band could be attributed to the combination of two excited molecules and the solvent between them (superexciplex). Moreover, the molecular structure, the energy bandgap, and the total energy of DAP was calculated using density functional theory

Key Generation and Secure Coding in Communications and Private Learning

The increasingly distributed nature of many current and future technologies has introduced many challenges for devices designed for such settings. Devices operating in such environments, such as Internet-of-Things (IoT), medical devices, connected vehicles, etc., typically have limited computational power and rely on batteries to operate. Therefore, efficiency is a paramount requirement for any algorithm designed to be implemented on these devices. Furthermore, these devices typically generate and collect huge amounts of extremely sensitive and personal data, such as health-related data, behavior-related data, etc. As a result, there is a need for security and privacy protections to guard against various attacks. Additionally, since these devices are typically resource-constrained, any algorithm or protocol needs to be efficient to enable its implementation on such devices. Efficient security and privacy solutions are essential to cope with, as well as enable, high deployment rate of such devices for various sensitive applications. In this dissertation, efficient solutions for protecting the security and privacy of data generated by such devices are explored. Low-complexity protocols for generating secret keys in static environments, along with a formulation of threshold-secure coding with a shared key and corresponding coding schemes are presented. Additionally, algorithms for coded machine unlearning for regression problems are presented, as well as a new setup and algorithm for federated learning with opt-out differential privacy are presented and evaluated.PHDElectrical and Computer EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/172704/1/aldaghri_1.pd

EPR steering and parameter estimation in the context of dephasing of two interacting qubits

The quantum steering and quantum Fisher information (QFI) for two qubits in the presence of qubits interaction and dephasing coupling is studied. We show how the dynamics of the quantumness measures can be influenced by the qubits interaction considering symmetry and asymmetry interaction between the environment and the qubits. We find that protection of the steering and enhancement of the parameter estimation precision (PEP) can be made through a proper choice of the quantum model parameters. Finally, we display the relationship between the fidelity, steering and QFI during the dynamics

Amplified Spontaneous Emission (ASE) Properties of a laser dye (LD-473) in solid state

The spectral characteristics of 1,2,3,8-tetrahydro-1,2,3,3,8-pentamethyl-5-(trifluoromethyl)-7H–pyrrolo[3,2-g]quinolin-7-one (LD-473) were demonstrated in liquid and solid states. For the liquid state, the absorption and fluorescence spectra of the LD-473 in Methyl Methacrylate showed bands at 385 and 420 nm, respectively. LD-473 in the solid state showed one absorption band at 530 nm, while the fluorescence spectra, under low concentration, showed one band at 615 nm. For higher concentrations, the fluorescence bands are shifted to the red. LD-473 in the solid state under an impulse of Nd: YAG laser showed dual amplified spontaneous emission (ASE) peaks at 605 and 650 nm. The longer wavelength coincided with a fluorescence peak while the shorter wavelength is an abnormal peak