For high technology companies such as Leonardo engaging in innovative research that might not produce a commercial return on investment for up to 10 years or beyond is vital. Our vision is to enable a paradigm shift in high-value low-volume remote sensing systems from concept to production: this requires a fusion of computational imaging concepts, that blur the traditional boundaries between sensing and signal processing, through-life digital modelling, that places innovative manufacture at the heart of the total system design and finally, individual AI/Robotic support, that multiplies the output of highly skilled production and maintenance personnel. The low volume, highly complex sensor systems produced by Leonardo present complex engineering challenges for design and production. Advances in machine learning, cobotics, novel materials, additive manufacturing, digital twinning and signal & image processing provide new paradigms for the end-to-end design and production processes and requires the development of a fully integrated digital design, assembly and manufacturing capability.

Precision timing is essential for accurate navigation and a large variety of civilian commercial and military infrastructure services including both small and large fixed and mobile platforms. These include: space, air, ground and marine vehicles, RADAR, reliable energy supply, safe transport links for air traffic control, network servers for data networks and electronic financial transactions. All of these are critical to the security and stability of the nation as many systems currently rely on large atomic clocks and the Global Navigation Satellite Systems (GNSS) for the timing signal. The aim of this project is to develop new types of atomic clock which offer enhanced timing in a compact and autonomous form-factor. This work will produce simplified Physics packages which when combined with state-of-the-arts flywheel oscillators produce highly accurate and stable compact atomic clocks. This high level of stability enables systems based on these clocks to operate independently of external sources.

In recent decades, atomic clocks have developed from being solely research instruments to indispensable and infrastructure-critical devices. Atomic clocks are now widely used in Global Navigation Satellite Systems (GNSS), data centres, power and mobile networks, financial markets for transaction time stamping, and research and development. Presently, many applications requiring high-precision timing rely on GNSS signals. However, this makes crucial infrastructure vulnerable to GNSS tampering and failure, with significant socio-economic consequences. Therefore, local high-performance atomic clocks are needed to safeguard against this. Other applications need to function in a GNSS-denied environment such as the navigation of submarines or electronic warfare and other security situations. Clock performance beyond GNSS capability is also required for state-of-the-art scientific research and advanced timekeeping. Current portable clocks currently have limited stability and accuracy or are too large and sensitive for applications on mobile platforms. While there has been immense progress in the miniaturisation of the laser systems and spectroscopy units for high-precision optical atomic clocks there are still two main challenges to overcome: The reference laser that requires a high-finesse optical cavity and the optical-frequency comb (OFC) that is required to convert the optical reference signal to a usable electronic signal. Here we propose to employ Raman transitions to create a highly stable and accurate atomic clock. In contrast to optical atomic clocks, the atomic reference stability is not transferred to the frequency of a single laser but is encoded in the frequency difference between two Raman lasers. This significantly relaxes requirements on the OFC and the optical cavity for the clock lasers. For the realisation of a THz-clock, we propose using calcium ions trapped in an RF ion trap and the Raman transition between the D3/2-level and the D5/2-level. The frequency splitting between these two states is 1.819 THz and the expected fractional frequency accuracy of the clock is better than 10-14 (systematic accuracy better than 1e-15) with a 20-litre form factor, significantly smaller than current optical clock systems. Due to its high accuracy in conjunction with small SWAP as well as robustness, this novel clock is exceptionally fit for applications on mobile platforms and in locations with low environmental control. Such portability, makes it particularly well suited for applications in the defence and security sector and as GNNS holdover clocks for telecom and utility networks as well as data centres and financial markets with holdover times of several months. Additionally, it enables novel schemes for frequency dissemination and synchronisation across large-scale telecom networks. Within this project, we will set up the THz-clock with equipment provided by CPI, characterise its performance and test the system in some application-relevant scenarios. CPI will perform environmental testing in their test facility, Leonardo will test the clock's performance on a mobile platform, and BT will investigate next-generation schemes for frequency dissemination and synchronisation across large optical fibre networks.

We have seen rapid development and growing interest in quantum technologies-based applications in the past decade and the overall global quantum technology market is expected to reach $31.57B by 2026. Most of these emerging quantum applications require single-photon avalanche diode (SPAD) detectors operating beyond the spectral range of silicon but with "silicon-like" performance. The use of "silicon-like" short-wave infrared (SWIR) SPAD detectors in the existing systems will immediately improve resolution and acquisition time for the existing imaging system and enhance the range and improve data rate for Quantum Key Distribution (QKD). However, the present commercially available InGaAs/InP based SPADs based on designs from more than two decades ago are unlikely to have a step change in their performance. Over the last five years, the advent of several innovations by way of novel III-V materials and semiconductor band structure engineering offers us the possibility of a paradigm shift in the performance of long wavelength detectors. The next revolution in the development of SPADs in the SWIR region will almost certainly be using novel materials and band structure engineered structures. Such a revolution will significantly enhance detection efficiency and fast timing. This new class of detectors will be evaluated on existing state-of-the-art testbeds for time-of-flight ranging/depth imaging and QKD. This Fellowship proposal has the ambition to sweep away the obstacles of material and processing problems that are hindering the development of affordable and easy operation SPADs, and to bridge gaps between material sciences, semiconductor physics, manufacturability and quantum technology applications in order to improve the scope and overall performance of next generation quantum technology-based applications.

Lasers are a key enabling technology in countless areas of modern society, touching on our lives in terms of ubiquitous connectivity, data storage, healthcare, security, environmental monitoring, etc. Examples include telecommunications, where they are used to generate the information carrying optical signals that are transmitted along thin glass optical fibres, manufacturing, where they are used for welding and cutting materials, and medicine, where they are used for sensing blood oxygen levels, and precisely resecting tissues. For almost all laser applications, it is necessary to use the laser source in combination with another technology that directs or "steers" the laser light in the desired direction. In some cases, this technology can be "passive", as is the case with the glass optical fibres used in telecommunications. In other cases, the steering technology must be "active" to change the direction of the laser beam in time, as is the case with the rapidly moving mirror systems used in some laser cutting and laser imaging systems. Conventional active laser steering technologies are often costly, bulky, and fragile. One or more of these disadvantages makes them sub-optimal for many important applications, including laser imaging systems for automotive applications, space-based laser communications systems, and drone-based remote sensing systems. To address this, there is currently a global drive to develop fully integrated solid-state beam-steering technologies, where the laser light is steered without the use of any physically moving components. Currently, however, even state-of-the-art solid-state laser beam steering systems have limited functionality, and do not meet the requirements of many real-world applications. In this project, we will exploit recent advances in two key integrated optical technologies - coherent Photonic Crystal Surface Emitting Laser (PCSEL) diode arrays and three-dimensional optical waveguide devices known as "integrated photonic lanterns" - to develop fully Integrated Solid-State Steerable Lasers (I-STEER) that can deliver agile beam steering in two dimensions and can, in principle, function at any diode laser wavelength. I-STEER will target the development of 900-mode PCSEL arrays, but will deliver the technological advances necessary to enable future PCSEL arrays (using commercial manufacturing facilities) that generate 10's of thousands of independently phase and ampltiude controllable coherent laser modes. A key aim of I-STEER is to enable denser PCSEL arrays, where the laser mode diameter is reduced to 20 microns (~20 wavelengths) and the centre-to-centre separation is reduced to ~50 microns (~50 wavelengths) - current PCSEL arrays exhibit 50 micron diameter laser modes with centre-to-centre separations of 400 microns. Unfortunately, even the ambitious spatial scales we are targeting mean that the PCSEL array will still be unsuitable for direct use as an optical phased array (OPA), since OPAs require very tightly packed wide angle emitters to achieve large angle/lobe free beam-steering. To address this, I-STEER introduces the fresh idea of using three-dimensional integrated optical waveguide transitions known as "integrated photonic lanterns" to adiabatically combine the PCSEL modes into a single highly multimode pattern of light, the spatial phase and amplitude properties of which can be directly controlled for beam steering via the PCSEL drive electronics. Through the I-STEER project, we aim to redefine the laser diode as an all-electronic integrated steerable light source enabling new functionally in countless applications including free-space optical communications and LiDAR. The generation of intellectual property and capability in this area will place the UK in a leading position with regards this strongly growing academic field, wealth generation through the creation of licensing and/or spin-outs, and in early adoption of UK based OEMs of this new technology.