Plasmonic metasurfaces provide unprecedented control of the properties of light. By designing symmetry-breaking nanoholes in a metal sheet and engineering the optical properties of the metal using geometry, highly selective transmission and polarisation control of light is obtained. To date such plasmonic filters have exhibited broad (> 200 nm) transmission linewidths in the NIR and as such are unsuitable for applications requiring narrow passbands, e.g. multi-spectral imaging. Here we present a novel subwavelength elliptical and circular nanohole array in a metallic film that simultaneously exhibits high transmission efficiency, polarisation insensitivity and narrow linewidth. The experimentally obtained linewidth is 79 nm with a transmission efficiency of 44%. By examining the electric and magnetic field distributions for various incident polarisations at the transmission peak we show that the narrowband characteristics are due

Complementary metal oxide semiconductor (CMOS) technology has made personal mobile computing and communications an everyday part of life. In this paper we present a nanophotonic integrated CMOS-based biosensor that will pave the way for future personalized medical diagnostics. To achieve our aim, we have monolithically integrated plasmonic nanostructures with a CMOS photodiode. Following this approach of monolithic nanophotonics–microelectronics integration, we have successfully developed a miniaturized nanophotonic sensor system with direct electrical readout, which eliminates the need of bulky and costly equipment that is presently used for interrogation of nanophotonic sensors. The optical sensitivity of the plasmonic nanostructures is measured to be 275 nm/refractive index unit (RIU), which translates to an electrical sensitivity of 5.8 V/RIU in our integrated sensor system. This advance is the first demonstration of monolithic integration of nanophotonic structures with CMOS detectors and is a crucial step toward translating laboratory based nanophotonic sensing systems to portable, low-cost, and digital formats.

As single-photon imaging becomes progressively more commonplace in sensing applications such as low-light-level imaging, three-dimensional profiling, and fluorescence imaging, there exist a number of fields where multispectral information can also be exploited, e.g., in environmental monitoring and target identification. We have fabricated a high-transmittance mosaic filter array, where each optical filter was composed of a plasmonic metasurface fabricated in a single lithographic step. This plasmonic metasurface design utilized an array of elliptical and circular nanoholes, which produced enhanced optical coupling between multiple plasmonic interactions. The resulting metasurfaces produced narrow bandpass filters for blue, green, and red light with peak transmission efficiencies of 79%, 75%, and 68%, respectively. After the three metasurface filter designs were arranged in a 64 × 64 format random mosaic pattern, this mosaic filter was directly integrated onto a CMOS single-photon avalanche diode detector array. Color images were then reconstructed at light levels as low as approximately 5 photons per pixel, on average, via the simultaneous acquisition of low-photon multispectral data using both three-color active laser illumination and a broadband white-light illumination source.

Biosensors for quick diagnosis and in situ monitoring are increasingly needed in health care. Field-effect transistor based biosensors have attracted much attention due to their high sensitivity and compatibility with point-of-care applications. As the most important 2D material, graphene has been investigated intensively as a channel material for transistor-based sensors due to its easily enhanced selectivity by rather simple functionalization. However, in order to realize its practical applications, challenges still remain, such as device stability and reproducibility. Here, we review recent progress in the general design strategy of high-performance graphene field-effect transistor biosensors with emphasis on the device physics, defects, Debye screening, and functionalization. Finally, both current applications and perspectives on future development are given.