Two-photon emission from a superlattice-based superconducting light-emitting structure.

Superconductor-semiconductor hybrid devices can bridge the gap between solid-state-based and photonics-based quantum systems, enabling new hybrid computing schemes, offering increased scalability and robustness. One example for a hybrid device is the superconducting light-emitting diode (SLED). SLEDs have been theoretically shown to emit polarization-entangled photon pairs by utilizing radiative recombination of Cooper pairs. However, the two-photon nature of the emission has not been shown experimentally before. We demonstrate two-photon emission in a GaAs/AlGaAs SLED. Measured electroluminescence spectra reveal unique two-photon superconducting features below the critical temperature (Tc), while temperature-dependent photon-pair correlation experiments (g(2)(τ,T)) demonstrate temperature-dependent time coincidences below Tc between photons emitted from the SLED. Our results pave the way for compact and efficient superconducting quantum light sources and open new directions in light-matter interaction studies.

An Electrically Pumped Topological Polariton Laser.

With a seminal work of Raghu and Haldane in 2008, concepts of topology have been introduced into optical systems, where some of the most promising routes to an application are efficient and highly coherent topological lasers. While some attempts have been made to excite such structures electrically, the majority of published experiments use a form of laser excitation. In this paper, we use a lattice of vertical resonator polariton micropillars to form an exponentially localized topological Su-Schrieffer-Heeger defect. Upon electrical excitation, the system unequivocally shows polariton lasing from the topological defect using a carefully placed gold contact. Despite the presence of doping and electrical contacts, the polariton band structure clearly preserves its topological properties. At high excitation power the Mott density is exceeded, leading to highly efficient lasing in the weak coupling regime. This work is an important step toward applied topological lasers using vertical resonator microcavity structures.

Cultural intelligence and proactive service performance: mediating and moderating role of leader's collaborative nature, cultural training and emotional labor.

PURPOSE: Drawing on cultural intelligence and social exchange theories, this study examines cultural intelligence and its effects on proactive service performance and the mediating role of leader's collaborative nature and the moderating role of cultural training and emotional labor, particularly deep acting and surface acting, in the relationship between cultural intelligence and proactive service performance. DESIGN/METHODOLOGY/APPROACH: The study sample comprised 510 healthcare practitioners. Structural equation modeling was used to examine the hypotheses. FINDINGS: The results show that cultural intelligence positively influences proactive service performance. Additionally, leadership's collaborative nature influences proactive service performance. The moderating effect of cultural training and deep acting positively influences the relationship between cultural intelligence and proactive service performance. In contrast, surface acting reveals a reverse effect, thus exhibiting a positive effect on this relationship. RESEARCH LIMITATIONS/IMPLICATIONS: These findings suggest that public healthcare organizations should pay more attention in improving deep acting, cultural training and leadership's collaborative nature for optimal service performance. ORIGINALITY/VALUE: The novelty of this study lies in its presentation of an integrated framework based on cultural intelligence and social exchange theories that can solve the contemporary challenges facing healthcare firms operating in emerging markets in integrating cultural intelligence and service performance.

The interplay of personality traits and motivation in leisure travel decision-making during the pandemic.

COVID-19 has negatively affected the travel and tourism industry and may continue to do so in the future. Therefore, hospitality businesses need to pay attention to consumer reactions, concerns, and motives for travelling in this era. This study leverages the stimulus-organism-behaviour-consequence (SOBC) model to examine psychological factors that influence Japanese travellers' intention to travel and willingness to pay premiums for safe travel by analysing data from 790 respondents. The findings of the study reveal that extraversion positively associates with introjected motivation and negatively with amotivation. Neuroticism personality type positively associates with amotivation and negatively associates with introjected motivation. Introjected motivation positively associates with perception of safe travel during COVID-19, whereas amotivation has a non-significant association with perception of safe travel during COVID-19. Perception of safe travel positively associates with intention to travel and willingness to pay premiums for safe travel. Finally, intention to travel has no effect on willingness to pay premiums for safe travel. These findings provide valuable theoretical and managerial implications.

Single-Photon Counting with Semiconductor Resonant Tunneling Devices.

Optical quantum information science and technologies require the capability to generate, control, and detect single or multiple quanta of light. The need to detect individual photons has motivated the development of a variety of novel and refined single-photon detectors (SPDs) with enhanced detector performance. Superconducting nanowire single-photon detectors (SNSPDs) and single-photon avalanche diodes (SPADs) are the top-performer in this field, but alternative promising and innovative devices are emerging. In this review article, we discuss the current state-of-the-art of one such alternative device capable of single-photon counting: the resonant tunneling diode (RTD) single-photon detector. Due to their peculiar photodetection mechanism and current-voltage characteristic with a region of negative differential conductance, RTD single-photon detectors provide, theoretically, several advantages over conventional SPDs, such as an inherently deadtime-free photon-number resolution at elevated temperatures, while offering low dark counts, a low timing jitter, and multiple photon detection modes. This review article brings together our previous studies and current experimental results. We focus on the current limitations of RTD-SPDs and provide detailed design and parameter variations to be potentially employed in next-generation RTD-SPD to improve the figure of merits of these alternative single-photon counting devices. The single-photon detection capability of RTDs without quantum dots is shown.

Antibiotic Resistance Pattern Of Acinetobacter Baumannii Isolated From Bacteremia Patients In Pakistan.

BACKGROUND: Acinetobacter baumannii causes a number of life-threatening infections in Hospitalized patients attributed to its ability to develop resistance against multiple antibiotics. The current scrutinisation is aimed to observe the prevalence and antibiotic resistance profile of A. baumannii strains isolated from blood of tertiary care Hospitalized patients in Lahore, Pakistan. METHODS: This research is a retrospective study conducted over a period of one year where 1864 blood samples were collected from both male and female patients with septicaemia. Total 156 A. baumannii species were identified by conventional method and their antimicrobial resistance pattern against 22 antimicrobials (representing all known classes of antibiotics) was evaluated by Kirby Bauer disc diffusion method. MICs of colistin, polymyxin B and vancomycin against A. baumannii were calculated by E test and broth dilution method. RESULTS: More males (n=97, 62%) were found infected than females (n=59, 38%). The spreading rate of A. baumannii was highest (n=101, 65%) in patients of age ≤20 years, and lowest (n=12, 7%) in the patients with the age of 41-60 years. Most of the strains of A. baumannii (n=118, 75.6%) were found to be MDR (multi drug resistant), 37 (23.7%) strains were XDR (Extensively drug-resistant) and only 1 (0.05%) strain was PDR (pandrug resistant). All the strains were sensitive to minocycline and tigecycline whereas highest non-susceptibility (n=144, 92%) was seen against Ampicillin-Sulbactam. Most of the strains demonstrated resistance against carbapenem and cephalosporin beckoning that A. baumannii can no longer be considered for salvage therapy by carbapenem. MICs of colistin, polymyxin B and vancomycin against A. baumannii divulged polymixin B as the most effective drug. CONCLUSIONS: Use of wide range of drugs has made A. baumannii multidrug resistant. Colistin, polymyxin B and vancomycin are the preferable drugs for the treatment of A. baumannii infections.

Elucidating the effects of organisational practices on innovative work behavior in UAE public sector organisations: The mediating role of employees' wellbeing.

In the context of the transitioning economy of the United Arab Emirates, which demands inculcating innovative behavior in public employees, this study investigates the relationship between high-involvement work practices and leaders' collaborative nature with employees' innovative behavior. Drawing on the social exchange and ability-motivation-opportunity theories, this research expounds the mediating effect of employees' wellbeing to examine the mechanisms through which high-involvement work practices and public leaders' collaborative nature affect employees' innovative behavior in public organisations. Using three-wave data from 207 individuals in public service organisations, this study tests the effects of employees' perceptions of high-involvement work practices and leaders' collaborative nature on their wellbeing and innovative work behaviors. Our findings have theoretical and practical implications for research on innovative work behavior in the milieu of public organisations.

Electronic and Optical Properties of InAs QDs Grown by MBE on InGaAs Metamorphic Buffer.

We present the optical characterization of GaAs-based InAs quantum dots (QDs) grown by molecular beam epitaxy on a digitally alloyed InGaAs metamorphic buffer layer (MBL) with gradual composition ensuring a redshift of the QD emission up to the second telecom window. Based on the photoluminescence (PL) measurements and numerical calculations, we analyzed the factors influencing the energies of optical transitions in QDs, among which the QD height seems to be dominating. In addition, polarization anisotropy of the QD emission was observed, which is a fingerprint of significant valence states mixing enhanced by the QD confinement potential asymmetry, driven by the decreased strain with increasing In content in the MBL. The barrier-related transitions were probed by photoreflectance, which combined with photoluminescence data and the PL temperature dependence, allowed for the determination of the carrier activation energies and the main channels of carrier loss, identified as the carrier escape to the MBL barrier. Eventually, the zero-dimensional character of the emission was confirmed by detecting the photoluminescence from single QDs with identified features of the confined neutral exciton and biexciton complexes via the excitation power and polarization dependences.

Metamorphic Buffer Layer Platform for 1550 nm Single-Photon Sources Grown by MBE on (100) GaAs Substrate.

We demonstrate single-photon emission with a low probability of multiphoton events of 5% in the C-band of telecommunication spectral range of standard silica fibers from molecular beam epitaxy grown (100)-GaAs-based structure with InAs quantum dots (QDs) on a metamorphic buffer layer. For this purpose, we propose and implement graded In content digitally alloyed InGaAs metamorphic buffer layer with maximal In content of 42% and GaAs/AlAs distributed Bragg reflector underneath to enhance the extraction efficiency of QD emission. The fundamental limit of the emission rate for the investigated structures is 0.5 GHz based on an emission lifetime of 1.95 ns determined from time-resolved photoluminescence. We prove the relevance of a proposed technology platform for the realization of non-classical light sources in the context of fiber-based quantum communication applications.

InP-Substrate-Based Quantum Dashes on a DBR as Single-Photon Emitters at the Third Telecommunication Window.

We investigated emission properties of photonic structures with InAs/InGaAlAs/InP quantum dashes grown by molecular beam epitaxy on a distributed Bragg reflector. In high-spatial-resolution photoluminescence experiment, well-resolved sharp spectral lines are observed and single-photon emission is detected in the third telecommunication window characterized by very low multiphoton events probabilities. The photoluminescence spectra measured on simple photonic structures in the form of cylindrical mesas reveal significant intensity enhancement by a factor of 4 when compared to a planar sample. These results are supported by simulations of the electromagnetic field distribution, which show emission extraction efficiencies even above 18% for optimized designs. When combined with relatively simple and undemanding fabrication approach, it makes this kind of structures competitive with the existing solutions in that spectral range and prospective in the context of efficient and practical single-photon sources for fiber-based quantum networks applications.

Anderson localisation in steady states of microcavity polaritons.

We present an experimental signature of the Anderson localisation of microcavity polaritons, and provide a systematic study of the dependence on disorder strength. We reveal a controllable degree of localisation, as characterised by the inverse-participation ratio, by tuning the positional disorder of arrays of interacting mesas. This constitutes the realisation of disorder-induced localisation in a driven-dissipative system. In addition to being an ideal candidate for investigating localisation in this regime, microcavity polaritons hold promise for low-power, ultra-small devices and their localisation could be used as a resource in quantum memory and quantum information processing.

Periodic squeezing in a polariton Josephson junction.

The use of a Kerr nonlinearity to generate squeezed light is a well-known way to surpass the quantum noise limit along a given field quadrature. Nevertheless, in the most common regime of weak nonlinearity, a single Kerr resonator is unable to provide the proper interrelation between the field amplitude and squeezing required to induce a sizable deviation from Poissonian statistics. We demonstrate experimentally that weakly coupled bosonic modes allow exploration of the interplay between squeezing and displacement, which can give rise to strong deviations from the Poissonian statistics. In particular, we report on the periodic bunching in a Josephson junction formed by two coupled exciton-polariton modes. Quantum modeling traces the bunching back to the presence of quadrature squeezing. Our results, linking the light statistics to squeezing, are a precursor to the study of nonclassical features in semiconductor microcavities and other weakly nonlinear bosonic systems.

Increased Photoconductivity Lifetime in GaAs Nanowires by Controlled n-Type and p-Type Doping.

Controlled doping of GaAs nanowires is crucial for the development of nanowire-based electronic and optoelectronic devices. Here, we present a noncontact method based on time-resolved terahertz photoconductivity for assessing n- and p-type doping efficiency in nanowires. Using this technique, we measure extrinsic electron and hole concentrations in excess of 10(18) cm(-3) for GaAs nanowires with n-type and p-type doped shells. Furthermore, we show that controlled doping can significantly increase the photoconductivity lifetime of GaAs nanowires by over an order of magnitude: from 0.13 ns in undoped nanowires to 3.8 and 2.5 ns in n-doped and p-doped nanowires, respectively. Thus, controlled doping can be used to reduce the effects of parasitic surface recombination in optoelectronic nanowire devices, which is promising for nanowire devices, such as solar cells and nanowire lasers.

Modulation doping of GaAs/AlGaAs core-shell nanowires with effective defect passivation and high electron mobility.

Reliable doping is required to realize many devices based on semiconductor nanowires. Group III-V nanowires show great promise as elements of high-speed optoelectronic devices, but for such applications it is important that the electron mobility is not compromised by the inclusion of dopants. Here we show that GaAs nanowires can be n-type doped with negligible loss of electron mobility. Molecular beam epitaxy was used to fabricate modulation-doped GaAs nanowires with Al0.33Ga0.67As shells that contained a layer of Si dopants. We identify the presence of the doped layer from a high-angle annular dark field scanning electron microscopy cross-section image. The doping density, carrier mobility, and charge carrier lifetimes of these n-type nanowires and nominally undoped reference samples were determined using the noncontact method of optical pump terahertz probe spectroscopy. An n-type extrinsic carrier concentration of 1.10 ± 0.06 × 10(16) cm(-3) was extracted, demonstrating the effectiveness of modulation doping in GaAs nanowires. The room-temperature electron mobility was also found to be high at 2200 ± 300 cm(2) V(-1) s(-1) and importantly minimal degradation was observed compared with undoped reference nanowires at similar electron densities. In addition, modulation doping significantly enhanced the room-temperature photoconductivity and photoluminescence lifetimes to 3.9 ± 0.3 and 2.4 ± 0.1 ns respectively, revealing that modulation doping can passivate interfacial trap states.

Self-catalyzed growth of GaAs nanowires on cleaved Si by molecular beam epitaxy.

Self-assembled GaAs nanowires have been grown on Si by molecular beam epitaxy without the use of any outside metal catalyst. The growth occurs on Si facets obtained by the cleavage of Si(100) substrates. The growth has been obtained with or without Ga pre-deposition. In both cases two kinds of nanowires have been obtained. The wires of the first type clearly present a Ga droplet at their free end and have a lattice structure that is wurtzite for wide regions beneath the Ga droplet. The second type, in contrast, ends with pyramidally shaped GaAs and has a crystal lattice that is mainly zincblende with only a few and small wurtzite regions, if any. The Ga-ended nanowires are longer than the others and thinner on average. The experimental findings suggest that the two types of nanowires grow after different growth processes.

Manganese-induced growth of GaAs nanowires.

GaAs nanowires have been grown on SiO2 and GaAs by molecular beam epitaxy using manganese as growth catalyst. Transmission electron microscopy shows that the wires have a wurtzite-type lattice and that alpha-Mn particles are found at the free end of the wires. X-ray absorption fine structure measurements reveal the presence of a significant fraction of Mn-As bonds, suggesting Mn diffusion and incorporation during wire growth. Transport measurements indicate that the wires are p-type, as expected from doping of GaAs with Mn.