Single Photons - Expanding the Spectrum (SPEXS)

Single-photon counting - the ability to faithfully capture the single quantum of light - is a critical capability for a wide range of new low-light sensing applications and a host of emerging photonic quantum technologies. This proposed Programme Grant aims to significantly expand the operational region of single-photon detectors well beyond silicon's 1000nm wavelength limit into the short-wave infrared (SWIR) region of wavelengths between 1400nm to 3000nm, and part of the mid-wave infrared (MWIR) region between 3000nm and 5000nm. By scaling up SWIR and MWIR semiconductor and superconductor single-photon detectors to large area focal plane arrays, we will produce revolutionary new cameras with picosecond timing resolution which can be used, for example, to see though fog in automotive lidar scenarios, as well as allowing imaging and sensing in new applications in environmental monitoring, healthcare, and security and defence.

The project will involve the design and fabrication of innovative new detector platforms of Ge-on-Si and III-V semiconductor detectors. The detectors are capable of single-photon sensitivity in the SWIR and MWIR regions, and will be fabricated in detector array format. We will also examine superconducting nanowires to expand their operation into the MWIR regions and fabricate arrayed detector configurations. A key part of the project is to integrate these arrayed detector technologies with read-out circuitry capable of rapid, low latency delivery of single-photon data. In addition, we will utilise micro-optic technology to optimise detection efficiency and demonstrate multiple wavelength filtering.

The cameras will be designed for use in a range of applications areas, including lidar, where the time-of-flight of the return photons can be used for the measurement of distance. In arrayed detector format, we will make cameras from which we will demonstrate three-dimensional imaging at long distance, where the sensitivity and time-resolution will enhance imaging through dense fog and other obscurants. We will demonstrate our detector technologies in quantum cryptography applications, where encryption keys can be shared between two users. By sending data encoded in single-photons it is possible for the sender and receiver to share a secure, random key known only to them. The most critical component in this form of quantum communication is the single-photon detector - we will demonstrate the use of our detectors both in optical fibre and free-space quantum key distribution scenarios. Other emerging applications in spectroscopy and biophotonics will be demonstrated.

This Programme Grant investigates innovative single-photon detection platforms and their applications in a range of emerging application areas in the short-wave and mid-wave infrared. This project will have an impact on society, industry, academia and the UK economy and will be used as a focus for engagement with international academia, industry and government stakeholders.

UK academia has a lead in a number of aspects of single-photon detection, single-photon lidar and quantum communications. We are well-placed to deliver outstanding impact beyond only academic research as UK industry starts to meaningfully engage with the single-photon community. This Programme Grant will deliver a realistic opportunity to create a UK manufacturing chain in picosecond resolution infrared single-photon cameras. This will bring obvious economic benefits to the UK, as we develop innovative new designs of cameras that can be manufactured in this country. These cameras can be used in a number of other products by UK end-users for applications in, for example: in automotive lidar; terrain mapping; hyperspectral imaging; environmental remote sensing; and healthcare. This Programme Grant has already engaged 17 industrial partners as part of the manufacturing chain or end-user community who have committed almost £1.7M in in-kind contributions. We will work closely with our Industry Partners and External Advisory Board to maximise impact and appropriately transfer the technology to industry. In addition to the advice from our Industry Partners, we will establish a portfolio of patents to help protect the intellectual property created in this Programme Grant.

The societal benefits of this Programme Grant will be wide-ranging. For example, short-wave infrared automotive lidar will eventually be used with other sensors to provide fully autonomous vehicles which will eventually play a key role in reducing the overall costs of transportation, with potentially huge societal benefits in terms of road safety, traffic congestion, pollution, freight transportation, and individual mobility. Short-wave infrared single-photon detectors can provide singlet oxygen explicit dosimetry - a key step in the photodynamic therapy of cancer. These detectors can be used for greenhouse gas mapping in the short and mid-wave infrared, giving valuable information for climate change analysis and pollution monitoring. There are a number of routes towards impact for a project that delivers such disruptive enabling optical detector platform technologies.