Adaptive motion artefact reduction in respiration and ECG signals for wearable healthcare monitoring systems

Wearable healthcare monitoring systems (WHMSs) have received significant interest from both academia and industry with the advantage of non-intrusive and ambulatory monitoring. The aim of this paper is to investigate the use of an adaptive filter to reduce motion artefact (MA) in physiological signals acquired by WHMSs. In our study, a WHMS is used to acquire ECG, respiration and triaxial accelerometer (ACC) signals during incremental treadmill and cycle ergometry exercises. With these signals, performances of adaptive MA cancellation are evaluated in both respiration and ECG signals. To achieve effective and robust MA cancellation, three axial outputs of the ACC are employed to estimate the MA by a bank of gradient adaptive Laguerre lattice (GALL) filter, and the outputs of the GALL filters are further combined with time-varying weights determined by a Kalman filter. The results show that for the respiratory signals, MA component can be reduced and signal quality can be improved effectively (the power ratio between the MA-corrupted respiratory signal and the adaptive filtered signal was 1.31 in running condition, and the corresponding signal quality was improved from 0.77 to 0.96). Combination of the GALL and Kalman filters can achieve robust MA cancellation without supervised selection of the reference axis from the ACC. For ECG, the MA component can also be reduced by adaptive filtering. The signal quality, however, could not be improved substantially just by the adaptive filter with the ACC outputs as the reference signals.Municipal Science & Technology Commission. Beijing Natural Science Foundation (Grants 3102028 and 3122034)General Logistics Science Foundation (Grant CWS11C108)National Institutes of Health (U.S.) (National Institute of General Medical Sciences (U.S.). Grant R01- EB001659)National Institutes of Health (U.S.) (National Institute for Biomedical Imaging and Bioengineering (U.S.) Cooperative Agreement U01- EB-008577

Roadmap on structured light

Structured light refers to the generation and application of custom light fields. As the tools and technology to create and detect structured light have evolved, steadily the applications have begun to emerge. This roadmap touches on the key fields within structured light from the perspective of experts in those areas, providing insight into the current state and the challenges their respective fields face. Collectively the roadmap outlines the venerable nature of structured light research and the exciting prospects for the future that are yet to be realized.Peer ReviewedPostprint (published version

Application of lasers to ultracold atoms and molecules

In this review, we discuss the impact of the development of lasers on ultracold atoms and molecules and their applications. After a brief historical review of laser cooling and Bose-Einstein condensation, we present important applications of ultra cold atoms, including time and frequency metrology, atom interferometry and inertial sensors, atom lasers, simulation of condensed matter systems, production and study of strongly correlated systems, and production of ultracold molecules.Comment: Review paper written in the name of IFRAF to celebrate 50 years of lasers and their applications to cold atom physics; 15 pages, 2 figures; to appear in Comptes Rendus de l'Academie des Sciences, Pari

Lasers and optics: Looking towards third generation gravitational wave detectors

Third generation terrestrial interferometric gravitational wave detectors will likely require significant advances in laser and optical technologies to reduce two of the main limiting noise sources: thermal noise due to mirror coatings and quantum noise arising from a combination of shot noise and radiation pressure noise. Increases in laser power and possible changes of the operational wavelength require new high power laser sources and new electro-optic modulators and Faraday isolators. Squeezed light can be used to further reduce the quantum noise while nano-structured optical components can be used to reduce or eliminate mirror coating thermal noise as well as to implement all-reflective interferometer configurations to avoid thermal effects in mirror substrates. This paper is intended to give an overview on the current state-of-the-art and future trends in these areas of ongoing research and development.NSF/PHY0555453NSF/PHY0757968NSF/PHY0653582DFG/SFB/407DFG/SFB/TR7DFG/EXC/QUES

An acoustic charge transport imager for high definition television applications

In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program

Exploiting multimode waveguides for pure fibre-based imaging

We acknowledge support from the UK Engineering and Physical Science Research CouncilThere has been an immense drive in modern microscopy towards miniaturisation and fibre based technology. This has been necessitated by the need to access hostile or diffcult environments in-situ and in-vivo. Strategies to date have included the use of specialist fibres and miniaturised scanning systems accompanied by ingenious microfabricated lenses. We present a novel approach for this field by utilising disordered light within a standard multimode optical fibre for lensless microscopy and optical mode conversion. We demonstrate the modalities of bright-field and dark-field imaging and scanning fluorescence microscopy at acquisition rates allowing observation of dynamic processes such as Brownian motion of mesoscopic particles. Furthermore, we show how such control can realise a new form of mode converter and generate various types of advanced light fields such as propagation-invariant beams and optical vortices. These may be useful for future fibre based implementations of super-resolution or light sheet microscopy.Publisher PDFPeer reviewe

Modeling and Simulation of Photonic Crystal Fibers and Distributed Feedback Photonic Crystal Fiber Lasers

A photonic crystal fiber (PCF) is comprised of a solid or air core surrounded by periodically arranged air holes running along the length of the fiber, which guides light in a fundamentally new way compared to conventional optical fibers, affecting almost all areas of optics and photonics. To analyze the dispersion and loss properties of PCFs, a two-dimensional (2D) finite-difference frequency-domain (FDFD) method combined with the technique of perfectly matched layer (PML) is developed. The propagation constant and loss can be obtained with accuracies in the orders of ∼10-6 and ∼10 -3, respectively. The Bragg fiber is a kind of PCF with alternate layers surrounding a solid or air core. To improve the performance of the above algorithm, a 1D FDFD method in the cylindrical coordinates is proposed to fully utilize the rotational symmetry property of the Bragg fiber. In addition to improving the accuracy, this method reduces the computation region from 2D to a straight line, significantly relieving the computation burden. A second method, called Galerkin method, is also developed under cylindrical coordinates. The mode fields are expanded using orthogonal Laguerre-Gauss functions; and the method is accurate and stable. However, it cannot do the loss analysis. For photonic-band-gap-guiding PCFs, the properties of the confined modes are closely related to the band structures of the cladding photonic crystals. Therefore, a third FDFD method using periodic boundaries is developed in a generalized coordinate system. Various lattice geometries are analyzed in the same manner, and the results are comparable to those obtained by the plane wave expansion method which is commonly used in the literature. Finally, a theoretical model for analyzing distributed feedback (DFB) PCF lasers has been presented. Two structures are investigated: PCFs with triangular lattice (TPCF) and PCFs made of capillary tube (CPCF). The modeling and simulation of erbium-doped and erbium/ytterbium (Er/Yb) co-doped DFB lasers are aimed at finding suitable PCF geometry to achieve low threshold and high output power. Various steps involved in this model are: (1) the properties of PCFs are analyzed by the FDFD method; (2) the Bragg grating is investigated by coupled mode theory; (3) the coupled wave equations are solved by transfer matrix method; and (4) Er atom is modeled as a three-level medium while energy transfer between Yb and Er atoms is considered for Er/Yb co-doped fiber. It is found that a CPCF laser with a smaller mode area is useful for lower-threshold applications and both of CPCF and TPCF lasers with larger mode areas are suitable for high-power operation