On-chip calibration and control of optical phased arrays

ptical phased arrays (OPAs) are important as they allow beam steering and scanning with no moving parts. As their channel count increases, the complexity of control and calibration becomes challenging. We propose an architecture and algorithm that provide rapid on-chip calibration and are scalable to arbitrary channel counts with significantly reduced chip area and reduced overall complexity compared to previously proposed approaches. The optimized phase shifter tuning algorithm - Deterministic Stochastic Gradient Descent (DSGD) - rapidly converges to the optimal state speeding up the digital-to-analog converter based control of large channel count OPAs

An Integrated-Photonics Optical-Frequency Synthesizer

Integrated-photonics microchips now enable a range of advanced functionalities for high-coherence applications such as data transmission, highly optimized physical sensors, and harnessing quantum states, but with cost, efficiency, and portability much beyond tabletop experiments. Through high-volume semiconductor processing built around advanced materials there exists an opportunity for integrated devices to impact applications cutting across disciplines of basic science and technology. Here we show how to synthesize the absolute frequency of a lightwave signal, using integrated photonics to implement lasers, system interconnects, and nonlinear frequency comb generation. The laser frequency output of our synthesizer is programmed by a microwave clock across 4 THz near 1550 nm with 1 Hz resolution and traceability to the SI second. This is accomplished with a heterogeneously integrated III/V-Si tunable laser, which is guided by dual dissipative-Kerr-soliton frequency combs fabricated on silicon chips. Through out-of-loop measurements of the phase-coherent, microwave-to-optical link, we verify that the fractional-frequency instability of the integrated photonics synthesizer matches the $7.0*10^{-13}$ reference-clock instability for a 1 second acquisition, and constrain any synthesis error to $7.7*10^{-15}$ while stepping the synthesizer across the telecommunication C band. Any application of an optical frequency source would be enabled by the precision optical synthesis presented here. Building on the ubiquitous capability in the microwave domain, our results demonstrate a first path to synthesis with integrated photonics, leveraging low-cost, low-power, and compact features that will be critical for its widespread use.Comment: 10 pages, 6 figure

The Genome of the Toluene-Degrading Pseudomonas veronii Strain 1YdBTEX2 and Its Differential Gene Expression in Contaminated Sand.

The natural restoration of soils polluted by aromatic hydrocarbons such as benzene, toluene, ethylbenzene and m- and p-xylene (BTEX) may be accelerated by inoculation of specific biodegraders (bioaugmentation). Bioaugmentation mainly involves introducing bacteria that deploy their metabolic properties and adaptation potential to survive and propagate in the contaminated environment by degrading the pollutant. In order to better understand the adaptive response of cells during a transition to contaminated material, we analyzed here the genome and short-term (1 h) changes in genome-wide gene expression of the BTEX-degrading bacterium Pseudomonas veronii 1YdBTEX2 in non-sterile soil and liquid medium, both in presence or absence of toluene. We obtained a gapless genome sequence of P. veronii 1YdBTEX2 covering three individual replicons with a total size of 8 Mb, two of which are largely unrelated to current known bacterial replicons. One-hour exposure to toluene, both in soil and liquid, triggered massive transcription (up to 208-fold induction) of multiple gene clusters, such as toluene degradation pathway(s), chemotaxis and toluene efflux pumps. This clearly underlines their key role in the adaptive response to toluene. In comparison to liquid medium, cells in soil drastically changed expression of genes involved in membrane functioning (e.g., lipid composition, lipid metabolism, cell fatty acid synthesis), osmotic stress response (e.g., polyamine or trehalose synthesis, uptake of potassium) and putrescine metabolism, highlighting the immediate response mechanisms of P. veronii 1YdBTEX2 for successful establishment in polluted soil

Bridging ultrahigh-Q devices and photonic circuits

Optical microresonators are essential to a broad range of technologies and scientific disciplines. However, many of their applications rely on discrete devices to attain challenging combinations of ultra-low-loss performance (ultrahigh Q) and resonator design requirements. This prevents access to scalable fabrication methods for photonic integration and lithographic feature control. Indeed, finding a microfabrication bridge that connects ultrahigh-Q device functions with photonic circuits is a priority of the microcavity field. Here, an integrated resonator having a record Q factor over 200 million is presented. Its ultra-low-loss and flexible cavity design brings performance to integrated systems that has been the exclusive domain of discrete silica and crystalline microcavity devices. Two distinctly different devices are demonstrated: soliton sources with electronic repetition rates and high-coherence/low-threshold Brillouin lasers. This multi-device capability and performance from a single integrated cavity platform represents a critical advance for future photonic circuits and systems

Integrated Photonics for NASA Applications

No abstract availabl

The unbundled university : researching emerging models in an unequal landscape

As higher education (HE) undergoes a massive expansion in demand in most countries across the globe and experiences financial pressures, the sector is evolving rapidly. Market pressures encourage the search for additional income and new forms of provision, and online programme management (OPM) companies are increasingly entering the sector as they identify market opportunities. At the same time, the HE sector has seen the appearance of many flexible online courses and qualifications delivered by new configurations of providers and partnerships, through a process of 'unbundling'. This chapter reports on the data on South African HE from the research project 'The Unbundled University: Researching emerging models in an unequal landscape'. Using a new dataset, mapping or social cartography is employed to bring a novel perspective to uncover patterns of new provision and the partnerships between OPMs and institutions and their relationship to differentiation in the HE sector. Significantly, the maps reveal relationships between universities and OPMs which appear to reflect existing differentiation between institutions, insofar as OPMs presently partner almost exclusively with historically advantaged, traditional universities, with high international ranking and reputation. This chapter argues that such partnerships have the potential to reinforce the power asymmetries already at play

Career guidance and the changing world of work: Contesting responsibilising notions of the future.

Career guidance is an educational activity which helps individuals to manage their participation in learning and work and plan for their futures. Unsurprisingly career guidance practitioners are interested in how the world of work is changing and concerned about threats of technological unemployment. This chapter argues that the career guidance field is strongly influenced by a “changing world of work” narrative which is drawn from a wide body of grey literature produced by think tanks, supra-national bodies and other policy influencers. This body of literature is political in nature and describes the future of work narrowly and within the frame of neoliberalism. The ‘changing world of work’ narrative is explored through a thematic analysis of grey literature and promotional materials for career guidance conferences. The chapter concludes by arguing that career guidance needs to adopt a more critical stance on the ‘changing world of work’ and to offer more emancipatory alternatives.N/

Does trust play a role when it comes to donations? A comparison of Italian and US higher education institutions

Higher education institutions (HEIs) have experienced severe cutbacks in funding over the past few years, with universities examining options for alternative funding streams, such as alumni funding. Identifying the factors influencing their alumni's intentions to invest in their alma mater can be of significant importance when establishing a sustainable revenue stream. Within this context, empirical research on the potential role of trust is scarce. This paper aims to deepen the analysis of the relationship between alumni trust and engagement as well as three outcomes, namely support, commitment, and attitude toward donation. A structural equation model was tested on two samples of US (  = 318) and Italian (  = 314) alumni. Although both countries are affluent and developed countries, the USA has an established tradition of alumni donations, which is not such a developed practice in Italy. For both countries, results confirm that engagement is an antecedent of trust, which in turn leads to the three investigated outcomes (support, commitment, and attitude toward donations). In contrast, the effect of commitment on attitude toward donations is significant only for the USA universities. The paper has interesting theoretical and managerial implications. From a theoretical point of view, the study aims to address a gap concerning the role of trust in the HE context. Managerially, the study has significant implications for universities that want to change alumni attitude toward donations. [Abstract copyright: © Springer Nature B.V. 2020.