Photonic ring resonators are miniature optical waveguiding structures that enable light to reach very high intensities in closed, circular paths. The loop structure and wave nature of light results in interference of the field such that the system becomes highly resonant with a repeated pattern. Each ring supports a comb of highly defined, specific frequencies of light, the spacing between which depends on the optical path length of the ring. In devices with a high-quality factor (high-Q), the optical circulating power can build up from a small milliwatt input signal to reach kilowatts of circulating power. The small, guided area of these devices results in immense power densities, permitting non-linear optical effects at remarkably low powers, despite the host material having low intrinsic non-linear properties. However, the achievable quality (Q) of such resonators has so far been limited by the losses caused by the absorption and scattering of light by the materials and structures used to fabricate the ring. The last 20 years have enabled significant progress in integrated photonics (optical circuits that guide and manipulate light analogous to the microchip in electronics), including the reduction of loss. Refined processes using CMOS-based cleanroom techniques have allowed researchers to improve optical transmission from 10% per metre to approximately 99.9% per metre in miniaturised optical chips. This has enabled the fabrication of optical microresonators with ultra-high-Q factors (over 100 million). These wafer-based devices form key components in advanced integrated photonic circuits for narrow linewidth lasers and frequency combs. The first generation of these devices has enabled compact systems for radar as well as for precision timing and navigation. Despite significant progress in the field, waveguide loss in state-of-the-art integrated photonics devices has plateaued at 100x higher losses than those readily achieved in standard telecoms optical fibre used for long-haul broadband internet. This limit is not fundamental but technological, and if fibre-like losses could also be achieved in an integrated photonics package, this would enable a new generation of applications and improvements in performance. These include compact, robust gyroscopes and low-power frequency combs for navigation and precision timing, ultra-narrow linewidth lasers (mHz to Hz), and advanced photonic components for telecommunication networks. This proposal seeks to combine the benefits of optical fibre fabrication approaches and material science developed over the past 50 years with the latest state-of-the-art CMOS fabrication techniques used for integrated optics. We aim to develop a manufacturing technique that will produce integrated ring resonator devices with the highest Q ever achieved. Using flame hydrolysis deposition and other standard optical fibre manufacturing techniques, we will develop ultra-pure glass layers to negate absorption losses. In particular, we will focus on high phosphorus and germanium doping, which we have shown can lead to dramatically better uniformity during our recent Caltech-Southampton DARPA seed project. We will use optical fibre manufacturing techniques to reduce loss from absorbed hydrogen and develop diffusion and reflow processes to remove waveguide interface and scattering losses. Our ambition is to develop the foundations for a scalable manufacturing process for the next generation of ultra-high-Q micro-ring resonators. These devices will enable a range of new technologies, including rugged miniature gyroscopes for navigation, combs for precision timing in data networks and optical sources for quantum technologies.

Gravitational waves (GWs) have changed the way we explore the cosmo. They have uncovered new types of astrophysical objects (black hole binaries, black hole-neutron star binaries), which we had imagined but never seen. Thanks to GWs, we are closer than ever before to understanding the state of matter in the densest stars, the fundamental nature of gravity, the structure of our Universe. These advances, made in less then a decade with only two detectors, show GW astronomy's unique potential: the ability to probe gravity at its extreme and, at the same time, large-scale astrophysics. The goal of this project is to exploit both of GW astronomy's strengths, delivering data analysis tools, analytic results and practical strategies. On the fundamental side, the project will address burning questions about the final stage of the merging of two black holes (the "ringdown"). Thanks to recent advances in perturbation theory, it is finally possible to understand - beyond leading order - how black holes settle down after a merger. This project will help fill-in one of the few missing blocks in the understanding of our century-old theory of gravity. This, together with practical strategies to distinguish new physics from old-fashioned astrophysics, will be essential to exploit near future (2023+) and future (2030s) GW observations. As an MSCA fellow, the applicant will receive crucial training in the fundamental aspects of gravity at the Nottingham Centre of Gravity (University of Nottingham). The Centre, whose expertise spans gravity, particle physics and cosmology, will be the ideal environment for this interdisciplinary project. The project's approach draws also from the applicant's expertise in theoretical physics and astrophysics, data analysis and numerical methods. An academic secondment at Caltech will complete the multifaceted training necessary for cutting-edge GW research, and will ensure the project's impact on key stakeholders, including current GW detectors.

Hopanoids are a poorly understood class of steroid-like molecules produced by bacteria. It has long been assumed that hopanes, molecular fossils of hopanoids, reveal a history of the rise of important microbial metabolisms such as oxygen-forming photosynthesis, but recent results from Prof. Dianne Newman's laboratory (California Institute of Technology) have challenged this interpretation. It is now apparent that our ability to interpret what hopanes reflect about geochemical and/or biological evolution is hindered by a poor understanding of their function within cells. Prof. Newman's studies of hopanoid formation and localisation in the hopanoid-producing bacterium Rhodopseudomonas palustris TIE-1, suggest that hopanoids play a crucial role in growth and cell division under certain conditions. To understand their biological roles at the molecular level, we require a chemical toolkit to study hopanoid localisation and to identify the proteins that bind them. Dr Conway and Prof. Newman aim to jointly develop this toolkit of molecules. The proposed research visit will allow Dr Conway to acquire the skills required to produce the starting point for this toolkit, improve some of the processes involved in purification and try some of the chemical reactions required to make the required molecular tools.

Synthetic biology is an emerging field of engineering that aims to establish a systematic framework for the design of biological systems based on a 'bottom-up' approach for the reconstruction of complex bio-molecular systems. The application of an engineering approach to design is attractive, as many engineering parallels can be identified in living systems. However, biological systems are highly complex and dynamic and difficult to engineer. Rapid characterization of particular biological parts and devices requires new methods as existing methods are inefficient and error prone, and require extensive time-consuming experiments. An alternative to current methods is the use ell-free systems for rapid characterization. Cell-free systems are cell extracts that contain all the machinery that allows biological parts to function and as such one can analyse many parts quickly without using living cells. This therefore speeds up the whole process. However, cell free systems can be variable and the results can be different between different researchers. The overall goal of this project is to further advance standardized cell-free systems using both computer models and new biochemical measurement tools. Such standardized systems will both explore the boundaries of cell-free prototyping and characterization, and enable more detailed understanding of key mechanisms, accelerating the usage and broader utility of cell-free systems in industry and academia.

Earthquakes, produced by rapid slip on faults, account for the majority of deaths from a range of natural disasters which amounts to about 60,000 people a year worldwide - around 90 percent of which occur in developing countries. Slip can occur in three ways on faults. These are (1) earthquake slip; (2) stable fault creep driven by plate tectonic loading rates; and (3) episodic slow slip events, where fault slip spontaneously accelerates but never reaches earthquake slip speeds. Episodic slow slip events can release the same amount of energy as earthquakes but over days to weeks rather than seconds to minutes. They most commonly occur in certain regions of subduction zones and have been linked to elevated pore pressures. These three modes of fault slip are vital to understand, as episodic slow slip and fault creep relieve stress build up and reduce seismic hazard, yet also transfer stress from one part of the fault to another, ultimately affecting the nucleation of destructive earthquakes. In this project, we will provide physical constraints from combined experiments and numerical modelling to determine the controlling factors leading to stable fault creep, episodic slow slip, or earthquakes. As yet, it is not understood what puts the brakes on some instabilities creating slow fault slip yet allows others to accelerate to rapid slip speeds that cause earthquakes. A transition of some sort from unstable frictional sliding (typically viewed as leading to earthquakes) to stable frictional sliding (typically viewed as leading to fault creep) while the sliding velocity is increasing must promote sustained slow slip on faults. The nature of this stability transition is widely debated and the range of conditions under which it may occur are ill defined. We will investigate the key hypotheses proposed to explain such stability transition and the resulting slow slip events, which include (1) evolution in friction properties related to very slow slip rates at elevated temperatures, (2) the role of pore fluid pressure on stability transitions, where small increases in pore volume of the granular shearing material in the fault produces a large decrease in pore pressure resulting in increase in the shear resistance (dilatant strengthening), and (3) spatial variation in fault properties and conditions leading to a situation where nucleation of an earthquake can occur but is limited by adjacent regions with stable frictional properties. The work will involve integrated laboratory experiments and numerical modelling. Controlled lab experiments will measure the evolution of fault friction under previously unexplored temperature, pore fluid pressure, and slip rate conditions relevant to natural faults. We will quantify the evolution of frictional properties from very slow, tectonic fault slip rates of millimetres per year, to those through the episodic slow slip range of millimetres per day, and into the slip rates of meters per second where earthquakes occur. Fluid pressure changes promoted by compaction and dilation during slip will also be characterized. Numerical modelling of the experiments at the laboratory scale will help to ensure that the coupled physical mechanisms involved are understood and captured in our mathematical descriptions. The large-scale behaviour of faults with the properties defined by the experiments will be explored by numerical modelling at the scale of natural faults. The numerical modelling will relate the experimental findings to field observations of episodic slow slip and earthquake nucleation and investigate the role of spatial variations in fault properties on the occurrence of episodic slow slip events vs. earthquakes. A key deliverable for this work would be identification of the range of fault conditions and physical mechanisms under which episodic slow slip, fault creep, or earthquakes can occur, leading ultimately to improved seismic hazard forecasting.