Photonic crystal cavities for integrated sensing

Slotted photonic crystals have shown in promise in the field of optical biosensing due to their ability to strongly confine light within the analyte itself. Recently, we have shown optimised coupling of light into the slot, integration with microfluidics, and the functionalisation and sensitive detection of binding on the crystal surface. We now show that these slotted photonic crystals can not only be used as the sensing element, but could also form part of the spectral read-out; the important next step to make a true lab-on-a-chip. In addition, we have been exploring other photonic crystal cavity designs and modes of operation for different types of biosensor. For example, multi-cavity arrays and out-of plane excitation of guided mode resonances can enable sensing at multiple locations within a small area. We review the principles of our various photonic crystal sensors, and our recent work to tackle real biological problems.