Phys.org August 28, 2023 Existing technologies for room-temperature detection of molecular vibrations in the mid-infrared rely on cooled semiconductor detectors because of thermal noise limitations. Researchers in the UK exploited molecular emitters possessing both MIR and visible transitions from molecular vibrations and electronic states, coupled through Franck–Condon factors. By assembling molecules into a plasmonic nanocavity resonant at both MIR and visible wavelengths, and optically pumping them below the electronic absorption band, they showed transduction of MIR light. The upconverted signal was observed as enhanced visible luminescence. Combining visible luminescence with enhanced rates of vibrational pumping gave transduction efficiencies of >10%. […]
Tag Archives: Cloaking
Quantum materials cloak thermal radiation
Nanowerk August 11, 2021 For most solids, the thermally emitted power increases monotonically with temperature in a one-to-one relationship that enables applications such as infrared imaging and noncontact thermometry. A team of researchers in the US (University of Wisconsin–Madison, Harvard University, Purdue University, Brookhaven National Laboratory) has demonstrated that ultrathin thermal emitters that violate this one-to-one relationship via the use of samarium nickel oxide (SmNiO3), a strongly correlated quantum material that undergoes a fully reversible, temperature-driven solid-state phase transition. Due to the smooth and hysteresis-free nature of this unique insulator-to-metal phase transition enabled them to engineer the temperature dependence of […]
Achieving invisibility: Cross-wavelength invisibility integrated with invisibility tactics
Phys.org September 30, 2020 Oceanic animals and their predators employ a cross-wavelength detection strategy. Inspired by these animals an international team of researchers (China, USA – UC Berkeley, Lawrence Berkeley National Laboratory, Duke University) proposed a new concept of cross-wavelength invisibility that integrated a variety of invisibility tactics. They presented a Boolean metamaterial design strategy to balance divergent material requirements across cross-scale wavelengths. As a proof of concept, they simultaneously demonstrated longwave cloaking and shortwave transparency using a nanoimprinting technique. The work extended stealth techniques from individual strategies of invisibility targeting a single-wavelength spectrum to integrated invisibility targeting cross-wavelength applications. […]
Image cloaking tool thwarts facial recognition programs
TechXplore August 5, 2020 To help individuals inoculate their images against unauthorized facial recognition models, researchers at the University of Chicago have developed a system called Fawkes. It helps individuals add imperceptible pixel-level changes (they call “cloaks”) to their own photos before releasing them. When used to train facial recognition models, the “cloaked” images produce functional models that consistently cause normal images of the user to be misidentified. In experiments Fawkes provided 95+% protection against user recognition regardless of how trackers train their models. They have shown that Fawkes is robust against a variety of countermeasures that try to detect […]
Magnetic Cloak Without Superconductors
American Physical Society Synopsys May 29, 2018 Magnetic cloaks typically use superconducting materials, which must be cooled to cryogenic temperatures. An international team of researchers (China, Sweden) has built a room-temperature cloak that does not employ superconductors. Such a cloak could be useful in shielding sensitive devices from external magnetic fields. Their cloak consists of a hollow cylinder made of several foils of a high-magnetic-permeability material with copper wires running along the cylinder’s length. When currents pass through the wires shields the interior of the cylinder from external magnetic fields. Experiments demonstrated that the device works at room temperature for […]