Double-cavity Fabry-Perot resonators based on one-dimensional silicon photonic crystals

This is the final version. Available from AIP Publishing via the DOI in this record.The 3rd Joint International Conference on Energy Engineering and Smart Materials (ICEESM-2018) and International Conference on Nanotechnology and Nanomaterials in Energy (ICNNE-2018)In this work we report on optical properties of Fabry-Pérot (FP) resonator based on Si-air one-dimensional photonic crystal (1D PC) with coupled double-cavity modes (or defects). These defects obtained by infiltration of the air-cavities of refractive index (nAir) with the filler of tunable refractive index. In the periodic structure of 1D PC, the filling of two defined grooves with a filler with a refractive index different from nAirleads to the appearance of two resonant modes, the position of which can be adjusted purposefully with changing of n filler. In comparison with (λ / 2) air resonators, the splitting of the doublet increases, which is explained by the increase in the coupling between the resonant modes due to the decrease in reflection R of the internal mirror. The coupled FP resonators design is CMOS compatible and has potential for application in tuning of individual transmission bands in wave-division multiplexing systems as well as for multiple narrow filters in the wide infrared spectral range.We acknowledge financial support from: The Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the EPSRC Grant No. EP/NO35569/1, and the Royal Society International Exchange Grant 2015/R3. The part of this research at the Ioffe Institute was supported by the Russian Federal Agency of Scientific Organizations

2D material liquid crystal nanocomposites for optoelectronic and photonic devices

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordWe synthesise, characterise and move toward application of 2D material liquid crystalline nanocomposites for optoelectronic and photonic devices, focussing on those produced using graphene oxide, tungsten disulfide and boron nitride

Phase-change band-pass filters for multispectral imaging

This is the author accepted manuscript. The final version is available from SPIE via the DOI in this recordPhase-change materials (PCMs) provide a route to adding dynamic tunability and reconfigurability to many types of photonic devices by changing the phase-state of the PCM itself. In this work we discuss the use of the phase-change alloy GeSbTe (GST) in the design of dynamically tunable filters operating in the infrared. GST is used to manipulate the extraordinary optical transmission of a periodic hole-array in a metallic layer, so creating ultra-thin, tunable band-pass filters. We discuss the use of such filters for multispectral imaging, suggest some approaches to overcome various practical challenges, and, finally, show that through the use of appropriate post processing algorithms this tunable filter could provide a cheap, ultra-thin, real-time, and relatively high performance multispectral imaging device.CDW acknowledges funding via the US Naval Research Laboratories ONRG programme (#N62909-16-1-2174) and the EPSRC ChAMP and WAFT grants (EP/M015130/1 and EP/M015173/1). LT acknowledges funding via the EPSRC CDT in Metamaterials (EP/L015331/1) and via QinetiQ PL

2D Material Liquid Crystals for Optoelectronics and Photonics

This is the author accepted manuscript. The final version is available from Royal Society of Chemistry via the DOI in this record.The merging of the materials science paradigms of liquid crystals and 2D materials promises superb new opportunities for the advancement of the fields of optoelectronics and photonics. In this review, we summarise the development of 2D material liquid crystals by two different methods; dispersion of 2D materials in a liquid crystalline host and the liquid crystal phase arising from dispersions of 2D material flakes in organic solvents. The properties of liquid crystal phases that make them so attractive for optoelectronics and photonics applications are discussed. The processing of 2D materials to allow for the development of 2D material liquid crystals is also considered. An emphasis is placed on the applications of such materials; from the development of films, fibers and membranes to display applications, optoelectronic devices and quality control of synthetic processes.We acknowledge financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the EPSRC Centre for Doctoral Training in Electromagnetic Metamaterials (Grant No. EP/L015331/1) and via Grant Nos. EP/N035569/1, EP/G036101/1 and EP/M002438/1

Multi-layer graphene as a selective detector for future lung cancer biosensing platforms

This is the final version. Available from the Royal Society of Chemistry via the DOI in this record.Highly selective, fast detection of specific lung-cancer biomarkers (CMs) in exhaled human breath is vital to the development of enhanced sensing devices. Today, e-nose is a promising approach for the diagnosis of lung cancer. Nevertheless, considerable challenges to early-stage disease diagnostics still remain: e.g. decrease in sensor sensitivities in the presence of water vapor, sensor drift leading to the inability to calibrate exactly, relatively short sensor lifetimes, and difficulty discriminating between multiple diseases. However, there is a wide scope for breath diagnostics techniques, and all advanced electrodes applicable to e-nose devices will benefit them. Here, we present the promising sensing capabilities of bare multi-layer graphene (MLG) as a proof of concept for advanced e-nose devices and demonstrate its utility for biomolecule discrimination of the most common lung CMs (ethanol, isopropanol, and acetone). We report on a comparative study involving exposure of the three CM solutions on flat MLG (f-MLG) and patterned MLG (p-MLG) electrodes, where the electrical conductivity of p-MLG is significantly increased while applying acetone. Based on sensitivity tests, we demonstrate the ability to monitor the electrical response of graphene electrodes employing graphene of various wettabilities. Specifically, the f-MLG electrode displays almost 2 times higher sheet resistance (30 Ω sq−1) compared to the hydrophilic p-MLG (12 Ω sq−1). We show significant sensitivity to selected specific molecules of pristine f-MLG and p-MLG while applying CM solutions with a 1.4 × 105 ppm concentration. Finally, we show the selectivity of f-MLG and p-MLG-based sensors when exposed to 2.0 × 105 ppm solutions containing different CM combinations. Both sensors were selective in particular to acetone, since the presence of acetone leads to a sheet resistance increase. We demonstrate that an advanced e-nose approach integrated with MLG electrodes has significant potential as a design concept for utilization of molecular detection at variable concentrations such as in early-stage disease diagnosis. This early-stage approach will provide convenient and reusable complex monitoring of CMs compared to typical contact sensors which require target analysis and are limited by disposable measuring. Moreover, further integration of the Internet of Things will introduce advanced e-nose devices as a biotechnological innovation for disease resilience with the potential for commercialization.Engineering and Physical Sciences Research Council (EPSRC)Engineering and Physical Sciences Research Council (EPSRC

Multi-channel Si-liquid crystal filter with fine tuning capability of individual channels for compensation of fabrication tolerances.

This is the final version. Available on open access from Springer via the DOI in this record.In this study, a technique for the optimization of the optical characteristics of multi-channel filters after fabrication is proposed. The multi-channel filter under consideration is based on a Si photonic crystal (PhC), tunable liquid crystal and opto-fluidic technologies. By filling air grooves in the one-dimensional, Si-Air PhC with a nematic liquid crystal, an efficiently coupled multi-channel filter can be realised in which a wide stop band is used for channel separation over a wide frequency range. By selectively tuning the refractive index in various coupled cavities, continuous individual tuning of the central channel (or edge channels) up to 25% of the total channel spacing is demonstrated. To our knowledge, this is the first report on the electro-optical solution for the compensation of fabrication tolerances in an integrated platform.This work has been supported by the ICGEE Programme (Ireland) and NAP-368 (Science Foundation Ireland)

Novel fluid materials for CMOS photonic WDM systems

We propose a simple and low-cost WDM (Wavelength division multiplexing) system (Fig 1a) based on novel fluid materials using micro-ring multichannel filter design with in-situ, electrically and magnetically tunable, integrated 2D liquid crystal nanocomposite materials. We achieved a quality factor on the order of 10# − 10% and fine tuning within the entire C-band range.Engineering and Physical Sciences Research Council (EPSRC

Smart Textile: Exploration of Wireless Sensing Capabilities

This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordE-textile is a developing technology joining the advantages of material science and information and communication technologies. In this work, we present the development and assessment of smart textile system containing sensing, processing and wireless communication capabilities. We demonstrate a wearable temperature sensing system based on resistance temperature detection approach utilizing graphene technology, which allows high flexibility and robustness of the electronic textile. The developed sensing system demonstrates experimental sensitivity as high as 80Ω/°C within the temperature detection range from 24 °C to 35 °C, which is the highest reported to date for wearable temperature sensors. In terms of wireless communication, the system operates at 2.4 GHz supporting Bluetooth low energy technology and securely transmits the measured data for up to 10 m which is proved by received signal strength and link quality indicators

Raman spectroscopy as a tool for characterisation of liquid phase devices

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordIn this paper, we demonstrate how Raman spectroscopy can be an effective tool for the elucidation of the properties of liquid phase devices, looking at signal enhancement through to beam profiling

Visible light emitting waveguide on Si chip

This is the author accepted manuscript. The final version is available from SPIE via the DOI in this record.Photonic lab-on-a-chip portable platforms have proved to be very sensitive, rapid in analysis and easy-to-use. However, they still rely on a bulk light source to operate, thus hindering the actual portability and potential for commercial realization. In the present paper we have proposed a design for a light emitting structure that could be easily implemented on chip. The design consists of a Si3N4 strip waveguide on SiO2 substrate, with an active material that emits light as top and lateral cladding. The cross-section of the waveguide was optimised to support both excitation and emission as guided modes, with a high mutual overlap and high confinement to the cladding. This ensures an efficient light emission activation from the cladding and a stable propagation along the waveguide. The proposed structure shows to be operative along the visible range; demonstrated from 400nm to 633nm. The procedure we have followed along this report can be virtually used for designing the cross-section geometry of any strip waveguide system so that the performance is optimised for a given cladding refractive index and emission and excitation wavelengths. In addition we have proposed the use of polymeric quantum dots as the gain material to be used as active cladding. The ease of on-chip integration of this gain material via spin-coating, together with the simplicity of our light emitting waveguide, makes our light source design suitable for large-scale integration on Si chip. Specially, for lab-on-chip applications where multiplexed operation is essential.This research was possible thanks to the Engineering and Physical Sciences Research Council (EPSRC) Centre for Doctoral Training in Electromagnetic Metamateriales at University of Exeter (Grant No. EP/L015331/1) and also via the EPSRC Grant EP/N035569/1