Mid-IR vibration-assisted luminescence & spectroscopies (MIRVALS)

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...