Nanoantenna Design for Enhanced Carrier-Envelope-Phase Sensitivity

Optical-field emission from nanostructured solids such as subwavelength nanoantennas can be leveraged to create sub-femtosecond, PHz-scale electronics for optical-field detection. One application that is of particular interest is the detection of an incident optical pulse's carrier-envelope phase. Such carrier-envelope-phase detection requires few-cycle, broadband optical excitation where the resonant properties of the nanoantenna can strongly alter the response of the near field in time. Little quantitative investigation has been performed to understand how the geometry and resonant properties of the antennae should be tuned to enhance the carrier-envelope phase sensitivity and signal to noise ratio. Here we examine how the geometry and resonance frequency of planar plasmonic nanoantennas can be engineered for enhancing the emitted carrier-envelope-phase-sensitive photocurrent when driven by a few-cycle optical pulse. We find that with the simple addition of curved sidewalls leading to the apex, and proper tuning of the resonance wavelength, the net CEP-sensitive current per nanoantenna can be improved by $5$-$10\times$, and the signal-to-noise-ratio by $50$-$100\times$ relative to simple triangular antennas operated on resonance. Our findings will inform the next generation of nanoantenna designs for emerging applications in ultrafast photoelectron metrology and petahertz electronics

Electron-Energy Loss of Ultraviolet Plasmonic Modes in Aluminum Nanodisks

We theoretically investigated electron energy loss spectroscopy (EELS) of ultraviolet surface plasmon modes in aluminum nanodisks. Using full-wave simulations, we studied the impact of diameter on the resonant modes of the nanodisks. We found that the mode behavior can be separately classified for two distinct cases: (1) flat nanodisks where the diameter is much less than the thickness; and (2) thick nanodisks where the diameter is comparable to the thickness. While the multipolar edge modes and breathing modes of flat nanostructures have previously been interpreted using intuitive, analytical models based on surface plasmon polariton (SPP) modes of a thin-film stack, it has been found that the true dispersion relation of the multipolar edge modes deviates significantly from the SPP dispersion relation. Here, we developed a modified intuitive model that uses effective wavelength theory to accurately model this dispersion relation with significantly less computational overhead compared to full-wave electromagnetic simulations. However, for the case of thick nanodisks, this effective wavelength theory breaks down, and such intuitive models are no longer viable. We found that this is because some modes of the thick nanodisks carry a polar (i.e. out of the substrate plane, or along the electron beam direction) dependence and cannot be simply categorized as radial breathing modes or angular (azimuthal) multipolar edge modes. This polar dependence leads to radiative losses, motivating the use of simultaneous EELS and cathodoluminescence measurements when experimentally investigating the complex mode behavior of thick nanostructures

Nanostructured-membrane electron phase plates

Electron beams can acquire designed phase modulations by passing through nanostructured material phase plates. These phase modulations enable electron wavefront shaping and benefit electron microscopy, spectroscopy, lithography, and interferometry. However, in the fabrication of electron phase plates, the typically used focused-ion-beam-milling method limits the fabrication throughput and hence the active area of the phase plates. Here, we fabricated large-area electron phase plates with electron-beam lithography and reactive-ion-etching. The phase plates are characterized by electron diffraction in transmission electron microscopes with various electron energies, as well as diffractive imaging in a scanning electron microscope. We found the phase plates could produce a null in the center of the bright-field based on coherent interference of diffractive beams. Our work adds capabilities to the fabrication of electron phase plates. The nullification of the direct beam and the tunable diffraction efficiency demonstrated here also paves the way towards novel dark-field electron-microscopy techniques and tunable electron phase plates

CDL Data Quality Assessment

Quality issues related to commercial driver license (CDL) data present ongoing challenges to state and federal transportation agencies. This study highlights several problems with CDL data, including a lack of standardization for state-specific traffic infractions; process and workflow difficulties that degrade the accuracy, validity, and timeliness of data; adjudication procedures that can potentially mask serious violations from CDL driver history records; inadequate recordkeeping in state law enforcement citation and court case management software applications; outdated mainframe systems in urgent need of upgrades; IT personnel who are not paid enough; and insufficient reporting requirements for federal agencies that issue traffic citations. Best practices states can adopt to resolve these issues include undertaking renewed efforts to standardize state traffic infraction codes and equivalency tables; increasing automation of data entry and reducing repetitive data entry processes; amplifying outreach efforts to law enforcement officials, prosecutors, and judges that are focused on the federal guidelines which govern the adjudication of CDL-related infractions and their application to driver history records; including a CDL indicator in citation and adjudication software so that researchers and analysts can better track how CDL-related traffic are handled; increasing investments in new IT systems as well as personnel recruitment and retention; and improving coordination between federal agencies and the Central Violations Bureau so that traffic citations are reported to state agencies quicker

Single-Photon Single-Flux Coupled Detectors

In this work, we present a novel device that is a combination of a superconducting nanowire single-photon detector and a superconducting multi-level memory. We show that these devices can be used to count the number of detections through single-photon to single-flux conversion. Electrical characterization of the memory properties demonstrates single-flux quantum (SFQ) separated states. Optical measurements using attenuated laser pulses with different mean photon number, pulse energies and repetition rates are shown to differentiate single-photon detection from other possible phenomena, such as multi-photon detection and thermal activation. Finally, different geometries and material stacks to improve device performance, as well as arraying methods are discussed

Developing a Baseline for Customer Satisfaction in the Kentucky Transportation Cabinet\u27s Department of Vehicle Regulation

Among the Kentucky Transportation Cabinet’s (KYTC) business units, the Department of Vehicle Regulation (DVR) has the most interactions with members of the public and other government agencies. Given its high profile and public visibility, it is critical for the department to provide high-quality customer service. Lacking data on customer perceptions of DVR’s level of service, the department commissioned researchers at the Kentucky Transportation Center (KTC) to conduct a baseline and rebaseline customer satisfaction surveys. Along with administering surveys to external customers, KTC’s research team also polled DVR staff to gauge employee morale and identify areas which could be improved. Approximately 90% of departmental staff believe that DVR provides a high level of customer service, and most viewed the department’s divisions favorably. Staff, however, noted the importance of fostering an open, equitable, and collaborative workspace as well as the importance of having up-to-date technological tools to perform daily job functions. With respect to the baseline and rebaseline external customer surveys, this study measured a slight decline in overall customer satisfaction. In the baseline survey, 81% of respondents were very or somewhat satisfied with the service they received; in the rebaseline survey 77% said the same. Regression modeling found a strong negative relationship between number of call escalations (i.e., call transfers) and customer satisfaction; call duration had a smaller but negative impact on customer satisfaction. Survey respondents expressed a growing preference for using electronic means (email, website) to interact with DVR. Moving forward, it will be critical for DVR to dedicate resources to improving its website and streamlining other modes of electronic communication, reducing the number of call escalations, and shortening average call durations – particularly hold times

Exploring British adolescent rugby league players' experiences of professional academies and dropout.

The purposes of this study were threefold: to explore former rugby league players’ experiences of professional academy environments, to understand their reasons for dropping out of the sport, and to explore their recommendations for optimising future talent development environments. Semi-structured interviews were conducted with nine ex-professional academy rugby league players up to one year after dropping out of playing rugby. A combination of inductive and deductive thematic analysis was employed to analyse the data. The thematic analysis revealed three general dimensions: talent development pathways, reasons for dropout, and recommendations. The findings suggest that players’ talent development experiences, and the reasons for dropout could be explained by a complex interaction of micro (e.g. negative academy experiences), meso (e.g. education), exo (e.g. player pathway structures), and macro systems (e.g. transitions to other clubs). It is concluded from these findings that talent development pathways which lack a long-term focus, and emphasise early success are likely to result in increased risk of burnout, de-motivation, and subsequent dropout. From an applied perspective, talent development pathways must consider the many personal and environmental factors which interact to determine an individual’s talent development trajectory. Furthermore, by recognising the multiple factors that may influence development, the effectiveness of development pathways may be enhanced by neither excluding “potential” through inappropriate early identification, nor ignoring crucial talent development variables that contribute toward the fulfilment of potential