Many aspects of modern life can be improved by rapid, non-contact identification of chemicals. To control and understand harmful gasses we need to detect transport emissions in real city environments and also map them across continents. To keep European citizens and infrastructure safe we need to be able to scan for traces of explosive or chemical weapons, without impractical physical checks. To bring to reality the science fiction of instant non-invasive medical diagnosis, we need to be able to detect subtle changes in biomarkers and metabolic processes under the skin or in our breath. Infrared (IR) spectroscopy can achieve this non-contact, real time, discriminatory chemical identification based on the “absorption fingerprints” all materials exhibit in the IR part of the spectrum. The specific chemical bonding structure in different materials absorbs at different wavelengths, generally between 3 to 12μm, defining the fingerprint.
The performance and form factor of practical IR spectroscopy systems are limited by their two key components the IR light source, typically a laser, and the IR detector. IR lasers have advanced tremendously in the last two decades. By contrast, core IR detector technology has changed little over the last 50 years. This project aims to develop of a new IR detector technology called a resonant cavity enhanced photodiode (RCE-PD), for IR spectroscopy applications. These novel detectors employ state of the art semiconductor and optical science to advance performance in much the same way as lasers advanced the performance of emitters. They promise at least a 10 times increases in signal-to-noise ratio. In practical systems this can either be used to improve overall system sensitivity and accuracy, or most excitingly to reduce the size and cooling requirements.
The need to cool high performance IR detectors is a major limitation on their application to mass-markets and deriving the potential societal benefits. The increased sensitivity of our novel RCE-PDs can be traded for increased operating temperature, allowing miniaturisation as a standard maintenance-free semiconductor technology. Once this is achieved, consumer applications can follow; as an example smart watches already use optical technology to monitor you pulse.
We will use our state of the art expertise and facilities to prototype RCE-PDs for two applications, one detecting methane, an important greenhouse gas and one detecting acetone, a biomarker associated with some metabolic disease process. The optical cavity defines the spectral selectivity, enhancing the optical field in a small volume of the detector. This maintains a high response to the incident light (signal), while reducing noise from leakage and background light, in comparison to established detector technologies. We will work with European National Laboratories, system developers and manufacturers to bring this breakthrough detector technology into transformational sensing systems and applications.