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Details of Grant 

EPSRC Reference: EP/Y008162/1
Title: Mid-IR vibration-assisted luminescence & spectroscopies (MIRVALS)
Principal Investigator: Baumberg, Professor JJ
Other Investigators:
Researcher Co-Investigators:
Project Partners:
AstraZeneca Cambridge Display Technology Ltd (CDT) Thermoteknix Systems Ltd
UK Centre for Ecology & Hydrology
Department: Physics
Organisation: University of Cambridge
Scheme: Standard Research
Starts: 01 January 2024 Ends: 31 December 2026 Value (£): 873,048
EPSRC Research Topic Classifications:
Materials Characterisation
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
EP/Y008774/1
Panel History:
Panel DatePanel NameOutcome
05 Jul 2023 EPSRC Physical Sciences Prioritisation Panel- July 2023 Announced
Summary on Grant Application Form
The aim of this proposal is to use the confinement of light to open up new possibilities in mid-infrared (MIR) detectors and use it to improve detection of rare analytes in environmental or biologically relevant fluids. Our key advance is how extreme light confinement controls MIR interaction with molecules, crucial in both aspects.

Detecting MIR light is vital for applications ranging from sensing of gases in the atmosphere to biomedical typing of tissues, since molecules absorb at characteristic vibrational bonds in the MIR. However sensitive detection of MIR light is problematic because unlike for visible light, detectors are bulky, costly and often need to be cooled. Room temperature detection of molecular vibrations in the MIR (3-30um wavelengths) has numerous applications including real-time gas sensing, chemical reactivity, medical and security imaging, astronomical surveys, and quantum communication. Sensitive pixelated detectors for imaging are extremely expensive (>£100k), precluding their use in many applications.

We have invented a new way to more efficiently detect MIR light, by upconverting it into the visible where efficient silicon cameras and detectors are ubiquitous. This breakthrough gives ten-fold cost reduction to existing technologies that would open up MIR sensing in many areas. While upconversion is known, it is low efficiency in all materials, which has required it to be enhanced using short pulse lasers that are also expensive, bulky, and costly. Our devices instead use extreme light confinement far below the optical wavelength into few-nm gaps between coinage metals (such as gold or silver). By confining both MIR and visible light in the same nano-gap, the upconversion efficiency is enhanced more than a billion-fold, enabling compact cheap detectors using diode laser or LED illumination. This leads to MIR detectors that are compact, uncooled, and much lower cost for users.

This grant is focussed on understanding how to trap both MIR light and visible light into the same gaps, how the constructs required can be easily, reliably, and cheaply constructed, and how to best understand their properties. We aim to build simple models that allow the tradeoffs between different design choices to be optimised, and to avoid the computationally expensive full simulations previously demanded.

In order to best understand the role of these coinage metal nano-gap cavities, we explore both the absorption of MIR light in molecules inside them, as well as how the molecules change their emission properties in response to MIR light. These two aspects of MIR science each give rise to promising MIR applications. One is detection of small concentrations (or changes) of analytes, for instance in the electrolytes within batteries which leads to their failure. Another is the detection of MIR light using uncooled array detectors capable for instance of imaging biopsy tissue slices.

The nanoscale architecture of our compressed optical cavities also gives an opportunity to avoid 'fouling', which is the buildup of organic molecules in active device regions. Our nanogaps only admit small molecules, and are electrically contacted (allowing application of voltages) while being robust to flow cleaning, opening new sensor paradigms.

We envisage many applications, but in truth this research is at the early stage where we do not yet know what is possible. What is crucial right now is that we employ scalable benign ways of making these, consider how they can be best recycled, and understand just how effectively such tiny devices can give far more efficient ways to utilise materials than our current paradigms.

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Organisation Website: http://www.cam.ac.uk