Integrated Photonics for Biomedical Spectroscopy

Integrated photonics is well advanced in applications from long-haul fibre telecommunications to data centres and from novel optical sources to chemical sensing. Silicon photonics [1] in particular has seen enormous growth in recent decades, but there is an increasing need for integrated photonic devices operating at longer wavelengths. Optical techniques are ubiquitous in providing chemical and biochemical information in a laboratory environment, but the demand for fast, low-cost, automated chemical analysis in applications from food safety and water quality to preventative medicine and rapid point-of-care diagnostics requires low-cost, compact devices and instruments with minimal user intervention for local and low-resource settings. The scale of integration, low cost and robustness of the microfabrication approaches which underpin consumer electronics is set to enable widespread deployment of miniaturised chemical and bioanalytical microsystems. However, biosensor and lab-on-chip research and commercialisation have been hampered by the lack of integrated photonic platforms which can operate over full the mid-infrared (MIR) fingerprint region from about 2μm to 18μm [2]. In particular the biomolecular “fingerprint” region from 5μm to 11μm would enable new opportunities for sensitive, selective, label-free biochemical analysis. Progress on new materials and approaches for high-sensitivity waveguide evanescent spectroscopies in the MIR will be described [3], and related to applications from therapeutic drug monitoring to cancer diagnostics [4]. Requirements for MIR components such as sources and detectors will also be considered briefly, to emphasise optical power budget and signal-to-noise requirements, which drive potential lower limits of detection