ABSTRACT
We show that ghost waves-a special class of nonuniform waves in biaxial dielectric media-can lead to exact frequency degeneracies in guided modes. These degeneracies offer a new way of controlling mode interactions with a broad range of potential applications, from integrated waveguides to nonlinear optics and optical sensing.
ABSTRACT
We show that perfect absorption of incoherent light is possible in a semi-infinite slab of anisotropic dielectric even in the presence of loss. The operating frequency of the proposed system is free of any dependence on physical dimensions.
ABSTRACT
An optical metamaterial is capable of manipulating light in nanometer scale that goes beyond what is possible with conventional materials. Taking advantage of this special property, metamaterial-assisted illumination nanoscopy (MAIN) possesses tremendous potential to extend the resolution far beyond conventional structured illumination microscopy. Among the available MAIN designs, hyperstructured illumination that utilizes strong dispersion of a hyperbolic metamaterial (HMM) is one of the most promising and practical approaches, but it is only theoretically studied. In this paper, we experimentally demonstrate the concept of hyperstructured illumination. A â¼80 nm resolution has been achieved in a well-known Ag/SiO2 multilayer HMM system by using a low numerical aperture objective (NA = 0.5), representing a 6-fold resolution enhancement of the diffraction limit. The resolution can be significantly improved by further material optimization.
ABSTRACT
GOAL: Although photoplethysmographic (PPG) signals can monitor heart rate (HR) quite conveniently in hospital environments, trying to incorporate them during fitness programs poses a great challenge, since in these cases, the signals are heavily corrupted by motion artifacts. METHODS: In this paper, we present a novel signal processing framework which utilizes two channel PPG signals and estimates HR in two stages. The first stage eliminates any chances of a runaway error by resorting to an absolute criterion condition based on ensemble empirical mode decomposition. This stage enables the algorithm to depend very little on the previously estimated HR values and to discard the need of an initial resting phase. The second stage, on the other hand, increases the algorithm's robustness against offtrack errors by using recursive least squares filters complemented with an additional novel technique, namely time-domain extraction. RESULTS: Using this framework, an average absolute error of 1.02 beat per minute (BPM) and standard deviation of 1.79 BPM are recorded for 12 subjects performing a run with peak velocities reaching as high as 15 km/h. CONCLUSION: The performance of this algorithm is found to be better than the other recently reported algorithms in this field such as TROIKA and JOSS. SIGNIFICANCE: This method is expected to greatly facilitate the presently available wearable gadgets in HR computation during various physical activities.
