Phys.org October 10, 2024 Rapid warming and increasing disturbances in high-latitude regions have caused extensive vegetation shifts and uncertainty in future carbon budgets. Better predictions of vegetation dynamics and functions require characterizing resilience, which indicates the capability of an ecosystem to recover from perturbations. A team of researchers in the US (The Ohio State University, University of Utah, Northern Arizona University) used temporal autocorrelation of remotely sensed greenness to quantify time-varying vegetation resilience during 2000–2019 across northwestern North American Arctic-boreal ecosystems. They found that vegetation resilience significantly decreased in southern boreal forests, including forests showing greening trends, while it increased […]
Engineering perovskite materials at the atomic level paves way for new lasers, LEDs
Phys.org October 11, 2024 Layered hybrid perovskites (LHPs) have emerged as promising reduced-dimensional semiconductors for next-generation photonic and energy applications where controlling the size, orientation, and distribution of quantum wells (QWs) is of paramount importance. A team of researchers in the US (North Carolina State University, Brookhaven National Laboratory) revealed that bulky molecular spacers act as crystal-terminating ligands to form colloidal nanoplatelets (NPLs) during early stages of LHP formation. They proved that NPLs ripen and grow, playing a decisive role in the time evolution of QW size, population distribution, and orientation. They demonstrated that antisolvent drip interrupts NPL ripening and […]
Harnessing quantum principles: Phased arrays within phased arrays for smarter, greener indoor optical wireless networks
Phys.org October 11, 2024 Researchers in Australia developed a novel approach for enhancing signal radiation patterns in optical wireless networks utilizing a planar optical aperture incorporated with infrared radiative element clusters to optimize signal radiation patterns through selective cluster excitation. They used dual carrier wavelength approach, leveraging an effectively large carrier wavelength for the system to avoid grating lobes occurrence due to distributed clusters. They used optimization-based algorithm to ensure optimized signal reception at the specific receiver location. Using simulations, they demonstrated the behavior of parameters like side lobe level, focal spot area, and power efficiency within the focal spot […]
Huge waves in the atmosphere dump extreme rain on northern Australia
Phys.org October 10, 2024 Convectively coupled equatorial waves (CCEWs) can be potential sources of predictability for sub-seasonal to seasonal prediction over northern Australia. Researchers in Australia studied the relationship between these waves and rainfall in northern Australia from 1981 to 2018. They found the waves had a significant impact on rainfall during the southern summer (December–February) and autumn (March–May). When waves combined in certain ways, heavy rain events become even more likely. Due to Australia’s vast landmass and local geography, the impacts of these waves were quite different across the continent. They showed that the activity of the “atmospheric melodies” […]
Hybrid fiber pump combiner could advance mid-IR laser systems
Phys.org October 9, 2024 Side-pumping fibre combiners offer several advantages in fibre laser design, including distributed pump absorption, reduced heat load, and improved flexibility and reliability. However, conventional fabrication methods face limitations due to significant differences in the thermal properties of pump-delivering silica fibres and signal-guiding fluoride-based fibres. Researchers in Germany addressed these challenges by introducing a design for a fuse-less side-polished (D-shaped) fibre-based pump combiner comprising multimode silica and double-clad fluoride-based fibres. The results demonstrated stable coupling efficiency over 8 hours of continuous operation under active thermal control. The pump combiner integrated into a linear Er-doped fibre laser cavity […]
Loss of lake ice has wide-ranging environmental and societal consequences, analysis suggests
Phys.org October 10, 2024 Most of the world’s lakes freeze, with a median ice duration of 218 days. The rate of lake ice loss has markedly accelerated over the past 25 years, with ice melt in some regions across the Northern Hemisphere arriving 45 days per century earlier and with many lakes experiencing increased intermittency of ice cover during winter in addition to ice-free winters. Lake ice loss is expected to affect a substantial proportion of the world’s population. Until recently, both logistical challenges as well as misconceptions of winter as a time of quiescence resulted in limited winter research. […]
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 […]
New method to generate photon pairs efficiently on a chip
Phys.org October 16, 2024 Thin-film lithium niobate is a promising platform for on-chip photon-pair generation through spontaneous parametric down-conversion (SPDC). However, device implementation faces practical challenges. Periodically poled lithium niobate (PPLN) suffers from poor fabrication reliability and device repeatability, while conventional modal phase matching (MPM) methods yield limited efficiencies. Researchers in Singapore introduced a layer-poled lithium niobate (LPLN) nanophotonic waveguide that significantly enhanced nonlinear interactions for MPM, and achieved normalized second-harmonic generation (SHG) conversion efficiency. Through a cascaded SHG and SPDC process, they demonstrated photon-pair generation with a normalized brightness in a 3.3 mm long LPLN waveguide. According to the […]
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 […]
Powerful and compact optical frequency combs provide unique opportunities
Phys.org October 11, 2024 Enhanced nonlinear processes in microresonators have emerged as a mainstream comb-generating mechanism with compelling advantages in size, weight, and power consumption. The established understanding of gain and loss in nonlinear microresonators, along with recently developed ultralow-loss nonlinear photonic circuitry, has boosted the optical energy conversion efficiency of microresonator frequency comb (microcomb) devices from below a few percent to above 50%. In this review an international team of researchers (USA – Caltech, Harvard University, Sweden) summarized the latest advances in novel photonic devices and pumping strategies that contributed to these milestones of microcomb efficiency. The resulting benefits […]