Sampled Fiber Gratings for High-Resolution and high-Speed Photonic Signal Processing

A novel sampled grating for high-resolution, highspeed signal processing is presented. Simulation based on Sinc2 sampled and rational sampled fiber grating modeling show that a large number of sub-ps time delay steps are attainable, corresponding to a sampling frequency in excess of 1THz. Design method is described for deriving sampling functions that meet specific true-time-delay profile requirements

Optical Magnetometer Employing Adaptive Noise Cancellation for Unshielded Magnetocardiography

This paper demonstrates the concept of an optical magnetometer for magnetocardiography. The magnetometer employs a standard Least-Mean-Squares (LMS) algorithm for heart magnetic field measurement within unshielded environment. Experimental results show that the algorithm can extract a weak heart signal from a much-stronger magnetic noise and detect the P, QRS, and T heart features and completely suppress the common power line noise component at 50 Hz

High sensitivity optically pumped quantum magnetometer

Quantum magnetometers based on optical pumping can achieve sensitivity as high as what SQUID-based devices can attain. In this paper, we discuss the principle of operation and the optimal design of an optically pumped quantum magnetometer. The ultimate intrinsic sensitivity is calculated showing that optimal performance of the magnetometer is attained with an optical pump power of 20 W and an operation temperature of 48°C. Results show that the ultimate intrinsic sensitivity of the quantum magnetometer that can be achieved is 327 fT/Hz1/2 over a bandwidth of 26 Hz and that this sensitivity drops to 130 pT/Hz1/2 in the presence of environmental noise. The quantum magnetometer is shown to be capable of detecting a sinusoidal magnetic field of amplitude as low as 15 pT oscillating at 25 Hz

Polymer chain distribution reorganization for improving the power conversion efficiency of polymer solar cells

We investigate the influence of the post solvent evaporation time delay on the performance of polymer solar cell (PSC) devices employing a bulk heterojunction photoactive polymer layer of regioregular poly(3-hexylthiophene) as electron donor and polymer [6,6]-thienylC61 butyric acid methyl ester as an electron acceptor. Characterization of the fabricated solar cell devices clearly demonstrates balanced transport of electrons and holes in the blend and confirms increased surface roughness and crystallinity of the films when post solvent evaporation time delay is optimised. An optimum device performance is obtained with 72 hours of post solvent evaporation time delay, achieving a power conversion efficiency of 4.1%, which is 0.9% higher than similar devices made without enough time for polymer-chaindistribution reorganization

Effect of vertically aligned carbon nanotube density on the water flux and salt rejection in desalination membranes

In this paper, vertically aligned carbon nanotube (VACNT) membranes of different densities are developed and their performances are investigated. VACNT arrays of densities 5 × 109, 1010, 5 × 1010 and 1011 tubes cm−2, are initially grown on 1 cm × 1 cm silicon substrates using chemical vapour deposition. A VACNT membrane is realised by attaching a 300 μm-thick 1 cm × 1 cm VACNT array on silicon to a 4″ glass substrate, applying polydimethylsiloxane (PDMS) through spin coating to fill the gaps between the VACNTs, and using a microtome to slice the VACNT–PDMS composite into 25-μm-thick membranes. Experimental results show that the permeability of the developed VACNT membranes increases with the density of the VACNTs, while the salt rejection is almost independent of the VACNT density. The best measured permeance is attained with a VACNT membrane having a CNT density of 1011 tubes cm−2 is 1203 LMH at 1 bar. © 2016, The Author(s)

Photonic Nano-Structures For Water Quality Monitoring

We propose a new type of sensors suitable for water quality testing and for monitoring water contamination levels in domestic, industrial and environmental applications. The proposed sensing scheme uses Fourier transform cavity-enhanced absorption spectroscopy and novel compact sensing elements based on nanostructured photonic crystal-type optical coatings enabling the sensitive Fourier-domain processing methodology and maximising the absorption path length within the measurement system. The measurement scheme is shown to be suitable for the determination of small changes in the water absorption coefficients at a discrete set of wavelengths in the visible spectral region in response to small concentrations of pollutants with high sensitivity. The proposed sensors are expected to provide real-time information on the water contamination levels, as well as potentially the types of substances dissolved

High contrast tandem organic light emitting devices employing transparent intermediate nano metal layers and a phase shifting layer

A high contrast-ratio organic light emitting device (OLED) is proposed and experimentally demonstrated. The OLED is implemented by stacking two organic phase tuning layers between composite metal layers and optimizing their thicknesses. Such a tandem device can increase the current efficiency by 120%, and reduce the operating voltage by 1.1 V, in comparison to conventional high contrast OLEDs. Measured reflection spectra validate the high-contrast capability of the OLED, and demonstrate experimentally an average reflectivity of 6% under ambient light illumination. This is the lowest reflectivity reported to date for OLEDs employing organic phase tuning layers

Reconfigurable Multi-Passband Optical Filter Using Opto-VLSI Processor

A reconfigurable multi-passband optical filter of 0.5 nm linewidth and a tuning range of 8 nm is demonstrated using an opto-VLSI processor. The wavelength tunability is performed using digital phase holograms uploaded on the opto-VLSI processor

Adaptive multi/demultiplexers for optical signals with arbitrary wavelength spacing

We propose and demonstrate the principle of a novel adaptive wavelength division multiplexer/demultiplexer structure based on Opto-VLSI processing. By driving an Opto-VLSI processor with an appropriate phase hologram, optical signals of arbitrary wavelengths from different input fiber ports can be multiplexed into a common output fiber port. In addition, wavelength division multiplexed channels of arbitrary wavelength spacings can also be demultiplexed and dynamically routed into arbitrary output fiber ports. A proof-of-principle 1×3 adaptive multiplexer/demultiplexers is experimentally demonstrated

Simultaneous monitoring of singlet and triplet exciton variations in solid organic semiconductors driven by an external static magnetic field

The research field of organic spintronics has remarkably and rapidly become a promising research area for delivering a range of high-performance devices, such as magnetic-field sensors, spin valves, and magnetically modulated organic light emitting devices (OLEDs). Plenty of microscopic physical and chemical models based on exciton or charge interactions have been proposed to explain organic magneto-optoelectronic phenomena. However, the simultaneous observation of singlet- and triplet-exciton variations in an external magnetic field is still unfeasible, preventing a thorough theoretical description of the spin dynamics in organic semiconductors. Here, we show that we can simultaneously observe variations of singlet excitons and triplet excitons in an external magnetic field, by designing an OLED structure employing a singlet-exciton filtering and detection layer in conjunction with a separate triplet-exciton detection layer. This OLED structure enables the observation of a Lorentzian and a non-Lorentzian line-shape magnetoresponse for singlet excitons and triplet excitons, respectively