Phys.org April 21, 2022 Waves entering a spatially uniform lossy medium typically undergo exponential intensity decay, arising from either the energy loss or the evanescent penetration during reflection. A team of researchers in the US (NIST, University of Maryland, Texas Tech University, Carnegie Mellon University) proposed and demonstrated exponential decay free wave propagation in a purely lossy medium. They observed up to 400-wave deep polynomial wave propagation accompanied by a uniformly distributed energy loss across a nanostructured photonic slab waveguide with exceptional points. Using coupled-mode theory and fully vectorial electromagnetic simulations they predicted deep wave penetration manifesting spatially constant radiation […]
Tag Archives: Sensors
Almost ready for prime time: Deep UV photodetectors head to real-world testing
Phys.org April 19, 2022 Researchers in India did a broad assessment of the performance of AlGaN and Ga2O3 photodetectors based on the material quality. They introduced a new comprehensive figure of merit (CFOM) to benchmark photodetectors by accounting for their three most critical performance parameters, i.e., gain, noise, and bandwidth. According to their benchmark AlGaN detectors do not have any serious shortcoming that is holding them back from entering the market. They tried to identify the gaps that exist in the research landscape of AlGaN and Ga2O3 solar-blind photodetectors and argue that merely improving the material/structural quality and device performance […]
Send in the Blow Flies: Using Insects to Sample Areas for Chemical Warfare Agents
Global Biodefense April 11, 2022 Blow flies sample the environment as they search for water and food sources and can be trapped from kilometers away using baited traps. Under a program sponsored by DARPA a team of researchers at Indiana University-Purdue University investigated blow flies as environmental chemical sample collectors following a chemical warfare attack (CWA). They exposed three species of blow flies to CWA simulants dimethyl methylphosphonate and diethyl phosphoramidate as well as the pesticide dichlorvos, followed by treatment-dependent temperature and humidity conditions to determine the persistence and detectability of these compounds under varying environmental conditions. Flies were sacrificed […]
‘Fingerprint’ machine learning technique identifies different bacteria in seconds
Phys.org March 4, 2022 Researchers in South Korea have demonstrated a markedly simpler, faster, and effective route to classify signals of two common bacteria E. coli and S. epidermidis and their resident media without any separation procedures by using surface-enhanced Raman spectroscopy (SERS) analysis boosted with a newly proposed deep learning model named dual-branch wide-kernel network (DualWKNet). With outstanding classification accuracies up to 98%, the synergistic combination of SERS and deep learning serves as an effective platform for “separation-free“ detection of bacteria in arbitrary media with short data acquisition times and small amounts of training data. Universal and fast bacterial […]
Metasurface-based antenna turns ambient radio waves into electric power
Phys.org February 28, 2022 Researchers at the South Florida University have demonstrated a high-efficiency RF energy harvesting device based on a metamaterial perfect absorber (MPA). With the embedded Schottky diodes, the MPA-based rectenna converts captured RF waves to DC power. The Fabry-Perot (FP) cavity resonance of the MPA greatly improved the amount of energy captured. The FP resonance exhibited a high Q-factor and significantly increased the voltage across the Schottky diodes, which improved the rectification efficiency, particularly at low intensity. This led to a factor of 16 improvement of RF-DC conversion efficiency at ambient intensity level. According to the researchers […]
Cooling matter from a distance
Science Daily February 2, 2022 Researchers in Switzerland succeeded in forming a control loop consisting of two quantum systems separated by one meter. Within this loop a vibrating membrane was cooled by a cloud of atoms, and the two systems were coupled to one another by laser light. As one of the systems acts as a control unit for the other, no measurement is needed. Instead, the control system is configured to bring the target system into a desired state by means of coherent quantum mechanical interaction. They successfully used this coherent feedback mechanism to reduce the temperature of the […]
Team demonstrates molecular electronics sensors on a semiconductor chip
Phys.com January 25, 2022 A team of researchers in the US (industry, UC San Diego, Rice University, Harvard University) has developed a molecular electronics platform which consists of a programmable semiconductor chip with a scalable sensor array architecture. Each array element consists of an electrical current meter that monitors the current flowing through a precision-engineered molecular wire, assembled to span nanoelectrodes that couple it directly into the circuit. The sensor is programmed by attaching the desired probe molecule to the molecular wire, via a central, engineered conjugation site. The observed current provides a direct, real-time electronic readout of molecular interactions […]
The perfect trap: a new way to control the polarization of light
Phys.org January 19, 2022 An international team of researchers (Germany, UK, Scotland, Switzerland) has demonstrated that the Kerr effect in a high-finesse Fabry-Pérot resonator can be utilized to control the polarization of a continuous wave laser. They showed that a linearly polarized input field is converted into a left- or right-circularly-polarized field, controlled via the optical power. The observations are explained by Kerr-nonlinearity induced symmetry breaking, which splits the resonance frequencies of degenerate modes with opposite polarization handedness in an otherwise symmetric resonator. According to the researchers in the future one could arrange many of these devices onto a photonic […]
This device could usher in GPS-free navigation
Phys.org October 26, 2021 Compact cold-atom sensors depend on vacuum technology. One of the major limitations to miniaturizing these sensors is the active pumps that are required to sustain the low pressure needed for laser cooling. Although passively pumped chambers have been proposed as a solution to this problem, technical challenges have prevented successful operation at the levels needed for cold-atom experiments. A team of researchers in the US (Sandia National Laboratory, University of Oklahoma) has demonstrated a vacuum package that is independent of ion pumps for more than a week. It can sustain a cloud of cold atoms in […]
BD21 Biosensor Redesign: DHS Seeks Contractors to Improve Urban BioThreat Classification Sensor
Global Biodefense September 3, 2021 The Biodefense for the 21st Century (BD21) program is working to design, develop, and deploy networked detection systems that continuously monitor the air, collect real-time data, and employ data analytics to detect anomalies. DHS has identified the need for further research and development of commercially available biological detection and presumptive identification technologies to enable timely detection and characterization of airborne bio-threats. The biosensors will be deployed both in indoor and outdoor urban environments to conduct real-time monitoring of biological threats. The redesign is to occur over 15 months and will take place in 2 phases. […]