Phys.org December 23, 2024 The effects of climate change on atmospheric circulation are more complex because the atmosphere is noisy and chaotic and thermodynamic changes can generate effects that make circulation changes difficult to decipher. According to an international team of researchers (USA – University of Chicago, NOAA, Boulder CO, University of Virginia, Germany, Australia, Switzerland, Israel, Finland) the circulation signals are an opportunity for improving our understanding of dynamical mechanisms, testing our theories and reducing uncertainties. The signals have also presented puzzles that represent an opportunity for better understanding the circulation response to climate change, its contribution to climate […]
Tag Archives: Light
Scientists observe ‘negative time’ in quantum experiments
Phys.org December 21, 2024 When a pulse of light traverses a material, it incurs group delay. Should the group delay experienced by photons be attributed to the time they spend as atomic excitations? However reasonable this connection may seem, it appears problematic when the frequency of the light is close to the atomic resonance, as the group delay becomes negative in this regime. An international team of researchers (Canada, Australia) used the cross-Kerr effect to probe the degree of atomic excitation caused by a resonant transmitted photon, by measuring the phase shift on a separate beam that was weak and […]
Tiny, wireless antennas use light to monitor cellular communication
MIT News December 20, 2024 Monitoring electrical potentials in liquid is critical in biosensing but limitations in spatial resolution and recording density remain. A team of researchers in the US (MIT, industry) introduced organic electro-scattering antennas (OCEANs) for wireless, light-based probing of electrical signals with micrometer spatial resolution, potentially from thousands of sites. The technology relied on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate light scattering properties to its doping level. Signal-to-noise ratios up to 48 were achieved in response to 100-mV stimuli. OCEANs demonstrated millisecond time constants and long-term stability, enabled continuous recordings over 10 hours. According to the researchers their work potentially accelerates […]
Infrared detectors made from quantum dots
Nanowerk December 3, 2024 Although hybrid graphene-colloidal PbS quantum dots (QDs) phototransistors are promising to overcome the geometrical restrictions of photodetectors to flat substrates, the experimental demonstration of their application to curved surfaces remains elusive. Researchers in Switzerland demonstrated the seamless integration of an infrared photodetector to a polymer optical fiber (POF), by wrapping graphene around the POF of 1 mm in diameter and, inkjet printing of PbS QDs onto the curved surface. The device acted as a functional coating and detected infrared light propagating through the POF without interrupting the waveguide. The ink supported drop-on-demand, and was colloidally stable […]
Light and symmetry study may offer opportunities for anti-counterfeiting
Phys.org November 29, 2024 An international team of researchers (the Netherlands, Greece) investigated the effect of a mirror-symmetry plane in multiple-scattering media under plane-wave illumination along the symmetry plane. Designed and fabricated samples’ optical transport properties were compared quantitatively with three-dimensional modeling. Strong polarization-dependent deviations of the bulk speckle-averaged intensity distribution at the symmetry plane showed either up to a factor 2 enhancement or complete suppression of the ensemble-averaged intensities. According to the researchers their work could have application in counterfeiting… read more. TECHNICAL ARTICLE
Microscopy at the tip of a hair-thin optical fiber: New approach pre-shapes light for unprecedented control
Phys.org December 3, 2024 Light transmission through a multimode fiber (MMF) has gained major importance for imaging and manipulation. Most phase retrieval algorithms used for a MMF implicitly assume light propagation to be described by a unitary operation, yet the transmission matrix of a multimode fiber is inherently non-unitary. An international team of researchers (UK, Australia) demonstrated that this assumption could impede the performance of many commonly used MMF phase retrieval algorithms and demonstrated that the weighted Yang–Gu algorithm outperformed other phase retrieval algorithms in this scenario. Once accounted for, the non-unitary property of the transmission matrix could be leveraged […]
Cooling with light: Exploring optical cooling in semiconductor quantum dots
Phys.org November 26, 2024 Highly efficient anti-Stokes (AS) photoluminescence (PL) is observed from halide perovskite quantum dots (QDs) due to their strong electron–phonon interactions. However, the PL quantum efficiency in QDs is primarily dominated by multiparticle nonradiative Auger recombination processes under intense photoexcitation, which impose limits on the optical cooling gain. Researchers in Japan investigated the Auger recombination of dot-in-crystal perovskites and quantitatively estimated the maximum optical cooling gain and the corresponding excitation intensity. Their optical cooling experiments demonstrated a maximum photo cooling of approximately 9 K from room temperature confirming that increasing the excitation intensity led to a transition […]
Novel AI algorithm captures photons in motion
Phys.org November 19, 2024 An international team of researchers (Canada, USA – Stanford University) presented an imaging and neural rendering technique that seeks to synthesize videos of light propagating through a scene from novel, moving camera viewpoints. They used a new ultrafast imaging setup to capture a first-of-its kind, multi-viewpoint video dataset with picosecond-level temporal resolution. Combined with this dataset, they introduced an efficient neural volume rendering framework based on the transient field defined as a mapping from a 3D point and 2D direction to a high-dimensional, discrete-time signal that represented time-varying radiance at ultrafast timescales. They rendered a range […]
New light-induced material shows powerful potential for quantum applications
Phys.org October 15, 2024 By using semiconducting hybrid perovskite as an exploratory platform, a team of researchers in the US (Northern Illinois University, Argonne National Laboratory) discovered that Nd2+ doped CH3NH3PbI3 (MAPbI3) perovskite exhibited a Kondo-like exciton-spin interaction under cryogenic and photoexcitation conditions. From a mechanistic standpoint, such extended charge separation states are the consequence of the trap state enabled by the antiferromagnetic exchange interaction between the light-induced exciton and the localized 4 f spins of the Nd2+ in the proximity. Importantly, this Kondo-like exciton-spin interaction can be modulated leading to exciton recombination at the dynamics comparable to pristine MAPbI3… read […]
Novel visible light communication encryption technology uses chiral nanoparticles
Phys.org October 10,2024 Although recent advancements have been made in active emission or passive conversion of polarized light through solution-processed nanomaterials or metasurfaces, the design paths usually encounter limitations. To address these challenges researchers in the Republic of Korea integrated the spatiotemporal modulation of the LED device, the precise control and efficient polarization emission, and the programmable patterning/positioning using 3D printing. They showed high degree of polarization for both linearly and circularly polarized emission from ultrathin inorganic nanowires and quantum nanorods due to the shear-force-induced alignment effect during the protruding of printing filaments. Real-time polarization modulation was obtained through the […]