Linear Geiger Mode Detector Technology for Time Resolved Spectral Measurements

The primary objective of this project is to develop an new class of detection system for cost effective time-resolved photon counting spectral measurement, initially aimed at time-resolved Raman spectroscopy (TRRS). TRRS is an established method to remove the delayed fluorescence signal from the prompt Raman photons, particularly for organic samples where the fluorescence signal is often much larger. Though very powerful as a sample analysis technique, TRRS has had limited uptake due to cost and complexity. Currently available TRRS systems separate the Raman and fluorescence signals by using either a gated Intensified CCD, or by using fast optical gating technology. Both approaches are complex, expensive and restricted to laboratory environments. This proposal aims to produce a new, smaller, cheaper class of detection system for TRRS and other time-resolved spectral measurements by integrating a SPAD linear array developed by the University of Sheffield with the fast readout electronics developed by the University of Leicester. Instead of gating, this system will provide the necessary time differentiation of Raman and fluorescence signals by photon time stamping.

Such an instrument is expected to open up new commercial applications in to fields ranging from security applications such as identification of counterfeit materials and pharmaceutical quality control, to biological applications including protein manufacture and potentially identification of cancer markers. A cost effective time-resolved Raman instrument would be disruptive technology with beneficiaries ranging from the project partners through commercial profit and licensing, suppliers of key components including commercial detector and high rep rate lasers from UK and European companies. Potential end-user beneficiaries include drug companies and their customers, the security services and general public through improved detection of hazardous and illegal materials, and public well-being through possible advances in cancer detection.

The detector system is also potentially game-changing for a number of other commercial applications. These include: LIDAR for 3D imaging and environmental monitoring; fluorescence lifetime imaging and related technologies for biological research, drug discovery and clinical diagnostics; and trace gas analysis using cavity enhanced absorption spectroscopy for pollution monitoring and medical diagnostics.

The project work is based on previous STFC-funded research into detectors and electronics at the Universities of Leicester and Sheffield and at CERN.

The Department of Electronic & Electrical Engineering at the University of Sheffield has been carrying out research into SPADs for over 15 years. Recent knowledge exchange activities include IR APD linear array with LIDAR Technology, X-ray APDs with University of Leicester, photodiodes/APDs for radiation thermometry with LAND Instrument International Ltd, and IR APD with Lasertel.

Previous STFC support has funded the PI, Lapington, to develop very high time resolution pixellated microchannel plate photomultiplier systems for commercial applications in the life science arena, based on a modular, multichannel high speed electronics with picosecond event timing resolution developed in collaboration with CERN. The electronics utilise two very high speed CERN-designed ASICs developed for the LHC-ALICE experiment in a modular design allowing systems with up to 1024 channels.

The University of Leicester and commercial partner, IS-Instruments, were recently awarded a TSB-funded "Emerging Imaging Technologies" feasibility study for preliminary investigation of this new technique for TRRS. This new project will move the technology from proof of concept to a commercial prototype for TRRS which will allow IS-Instruments to commercialise a new suite of spectrometer systems capable of separating signals in time, generating the potential for cost effective, hand-held TRRS spectrometer.