A range of nanophotonic sensors composed of different materials and device configurations have been developed over the past two decades. These sensors have achieved high performance in terms of ...sensitivity and detection limit. The size of onchip nanophotonic sensors is also small and they are regarded as a strong candidate to provide the next generation sensors for a range of applications including chemical and biosensing for point-of-care diagnostics. However, the apparatus used to perform measurements of nanophotonic sensor chips is bulky, expensive and requires experts to operate them. Thus, although integrated nanophotonic sensors have shown high performance and are compact themselves their practical applications are limited by the lack of a compact readout system required for their measurements. To achieve the aim of using nanophotonic sensors in daily life it is important to develop nanophotonic sensors which are not only themselves small, but their readout system is also portable, compact and easy to operate. Recognizing the need to develop compact readout systems for onchip nanophotonic sensors, different groups around the globe have started to put efforts in this direction. This review article discusses different works carried out to develop integrated nanophotonic sensors with compact readout systems, which are divided into two categories; onchip nanophotonic sensors with monolithically integrated readout and onchip nanophotonic sensors with separate but compact readout systems.
A broad linewidth and a lack of spectral analysis limit the applications of plasmonic sensors. In this Letter, a plasmonic sensor with a large sensitivity in the terahertz (THz) range is proposed ...based on high-quality factor (>1000) surface lattice resonance in subwavelength near-flat metallic gratings. Moreover, such a highly selective spectral manipulating scheme, plus the greatly localized plasmonic resonance, enables miniaturized spectroscopy based on a single detector by integrating an electro-optical material with the gratings. A spectral resolution of 0.1 GHz at a center frequency of 1.1 THz is predicted showing a four times improvement of measuring efficiency. This technique shows promising potential in on-site matter inspection and point-of-care testing.
We experimentally demonstrate a CMOS compatible medium wave infrared metal-insulator-metal (MIM) metamaterial absorber structure where for a single dielectric spacer thickness at least 93% absorption ...is attained for 10 separate bands centred at 3.08, 3.30, 3.53, 3.78, 4.14, 4.40, 4.72, 4.94, 5.33, 5.60 μm. Previous hyperspectral MIM metamaterial absorber designs required that the thickness of the dielectric spacer layer be adjusted in order to attain selective unity absorption across the band of interest thereby increasing complexity and cost. We show that the absorption characteristics of the hyperspectral metamaterial structures are polarization insensitive and invariant for oblique incident angles up to 25° making them suitable for practical implementation in an imaging system. Finally, we also reveal that under TM illumination and at certain oblique incident angles there is an extremely narrowband Fano resonance (Q > 50) between the MIM absorber mode and the surface plasmon polariton mode that could have applications in hazardous/toxic gas identification and biosensing.
Fluorescence Imaging (FI) is a powerful technique in biological science and clinical medicine. Current FI devices that are used either for in-vivo or in-vitro studies are expensive, bulky and consume ...substantial power, confining the technique to laboratories and hospital examination rooms. Here we present a miniaturised wireless fluorescence endoscope capsule with low power consumption that will pave the way for future FI systems and applications. With enhanced sensitivity compared to existing technology we have demonstrated that the capsule can be successfully used to image tissue autofluorescence and targeted fluorescence via fluorophore labelling of tissues. The capsule incorporates a state-of-the-art complementary metal oxide semiconductor single photon avalanche detector imaging array, miniaturised optical isolation, wireless technology and low power design. When in use the capsule consumes only 30.9 mW, and deploys very low-level 468 nm illumination. The device has the potential to replace highly power-hungry intrusive optical fibre based endoscopes and to extend the range of clinical examination below the duodenum. To demonstrate the performance of our capsule, we imaged fluorescence phantoms incorporating principal tissue fluorophores (flavins) and absorbers (haemoglobin). We also demonstrated the utility of marker identification by imaging a 20 μM fluorescein isothiocyanate (FITC) labelling solution on mammalian tissue.
We report on the design and fabrication of a hybrid sensor that integrates transmission-mode localized surface plasmonic resonance (LSPR) into a quartz crystal microbalance (QCM) for studying ...biochemical surface reactions. The coupling of LSPR nanostructures and a QCM allows optical spectra and QCM resonant frequency shifts to be recorded simultaneously and analyzed in real time for a given surface adsorption process. This integration simplifies the conventional combination of SPR and QCM and has the potential to be miniaturized for application in point-of-care (POC) diagnostics. The influence of antibody-antigen recognition effect on both the QCM and LSPR has been analyzed and discussed.
•We hybridised a LSPR and QCM sensor that simultaneously records the optical and acoustic signal in real time for a given surface adsorption process to eliminate the variations of the experimental conditions.•We detailed the design and simulation of the hybridised LSPR and QCM device and experimentally assess its performance. The experimental data match well with the simulations, further proving the design concept.•We used the hybridised chip in a biologically relevant immunoassay showing its potential for practical biosensing.•Our technology provides a miniaturized dual sensor platform for simultaneous measurement that is compatible with incorporation into future point-of-care and portable devices.
Significant improvement in using plasmonic nanostructures for practical color filtering and multispectral imaging applications is achieved by exploiting the coupling of surface plasmons with ...dielectric optical cavity resonances within a hexagonal array of subwavelength holes in a thin CMOS-compatible metal–insulator–metal stack. This polarization-independent architecture overcomes the limitations of all previously reported plasmonic color filters, namely poor transmission and broad band-pass characteristic, effectively providing a compact approach for high color accuracy multispectral and filtering technologies. Measured transmission efficiencies up to 60% and full-width at half-maximum between 45 and 55 nm along the entire visible spectrum are achieved, an impressive and unique combination of features that has never been reported before. The nanostructure exploits the phenomenon of extraordinary optical transmission and magnetic dipole modes to efficiently filter visible light. The presence of magnetic resonances in the optical regime is an unusual property, previously reported in photonic metamaterials or dielectric nanoparticles. The physical insights established from the electromagnetic near-field patterns are used to accurately tailor the optical properties of the filters. The nonideality of the fabrication at the nanoscale is addressed, the issues encountered highlighted, and alternative solutions proposed and verified, demonstrating that the working principle of the MIM structure can be successfully extended to other materials and structural parameters.
The transformation of nanophotonic sensors from laboratory-based demonstrations to a portable system to ensure widespread applicability in everyday life requires their integration with detectors for ...direct electrical read out. As complementary metal oxide semiconductor (CMOS) technology has revolutionized the electronics industry, the integration of nanophotonic structures with CMOS technology will also transform the sensing market. However, nanophotonic sensors have to fulfill certain requirements for their integration with CMOS detectors, such as operation in the visible wavelength range, operation in normal incidence configuration, use of CMOS compatible materials, and capability to give large optical intensity change due to resonance wavelength shift. In this paper, we have designed and developed one-dimensional silicon nitride grating structures that satisfy all these conditions simultaneously. The gratings can achieve 1 and 6 nm linewidths for the transverse-electric (TE) and transverse-magnetic (TM) polarizations, respectively, with 90% resonance depth. The experimental linewidth is 8 nm with 55% resonance depth, which is limited by the detector resolution. The experimental sensitivity of the device is 160 nm/refractive index unit (RIU), which translates to a very high intensity sensitivity of 1700%/RIU, which would enable sensing of very small changes in refractive index when integrated with a detector.
This paper presents an approach for matching the transconductance characteristics of CMOS ISFET arrays by removing trapped charge. We describe how to design arrays of floating-gate ISFETs so that ...ultraviolet (UV) radiation and bulk-substrate biasing can be used to remove the random amount of trapped charge that accumulates on the gates during fabrication. The approach is applied directly to a prototype single-chip 2 2 array of ISFETs, which is designed and fabricated in a standard 0.35- CMOS process. By considering the transconductance characteristics of the 2 2 array before and after UV exposure, it is shown that the response can be matched after 10 h and that the ISFET threshold voltages converge to an equilibrium value of approximately 1 V. After matching, it is found that the ISFET array has a measured sensitivity of 46 mV/pH and can successfully image a change in the pH of a homogeneous electrolyte solution.
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