Efficient manipulation of the valley degree of freedom in Transition Metal Dichalcogenide (TMD) monolayers at the nanoscale becomes very desirable for future developments in valleytronics. Resonant optical nanostructures are considered as potential tools in this endeavor; however, it is still unclear how they affect polarization properties of valley-specific monolayer emission. Here, we present a systematic experimental and numerical study that is aimed to bridge this gap. As a simple model, we consider a hybrid system where valley-polarized photoluminescence [1] or second harmonic from MoS2 - monolayer is coupled with a plasmonic nanosphere. Through this study, we are not only aimed to refine the exciting simulation approaches for valleytronic devices, but also contribute to the deeper understanding of the rich physics of light-matter interactions at the nanoscale.
Previous studies in optoretinography often rely on AO-OCT systems to resolve individual cells or use intensity-based image processing to extract the dynamics of the retinal layer as an ensemble. For non-AO point-scan OCT, investigating tissue dynamics from obscure speckle patterns while preserving the spatial heterogeneity of signals remains challenging. Here, we developed phase-restoring subpixel image registration and unsupervised machine learning algorithms to accurately extract spatially-resolved OCT phase signals from the outer retina in rodents. In addition to observing light-evoked deformation of the photoreceptors outer segments, we discovered an optical signature of the retinal pigment epithelium (RPE) response to visual stimuli.
In-vivo imaging of the light-evoked responses of retinal cells in rodents can provide valuable insights into the correlation between optoretinography (ORG) signals and retinal degeneration. However, interpreting outer retina dynamics in rodents is challenging due to the limited resolution of optical coherence tomography, which often results in the superposition of outer retinal layers, such as the rod outer segment (ROS), retinal pigment epithelium (RPE), and Bruch’s membrane, within speckle patterns. Here, we present an automated, unbiased approach for extracting spatially-resolved outer retinal dynamics from complicated speckle patterns. Using this approach, we revealed the light-evoked dynamics of both ROS and RPE in rodents.
Small animals, such as rodents, are attractive options for investigating the intrinsic process of retinal degeneration. In this study, we used phase-sensitive optical coherence tomography to explore the comprehensive dynamics of rats’ outer retinas in response to visual stimuli. By calculating the temporal phase difference between different outer retinal bands, we revealed highly reproducible retinal dynamics, on the order of tens of nanometers, related to different parts of the outer retina. Our approach may pave the way for preclinical optoretinography study in small animals, facilitating clinical translations for the early detection of neurodegenerative diseases.
Numerous efforts have been recently undertaken towards the development of rectifying devices operating at high frequencies especially dedicated to light harvesting and photo detection applications. To this end various rectification strategies have been implemented, such as laser-induced STM tunneling, metal-insulator-metal (MIM) travelling wave diodes, plasmonic nanogap optical antennas, antenna-diode coupled planar MIM, and MIM point-contact sharp-tip or whisker diodes. However, developing high frequency rectifying antennas (rectennas) remains a major technological challenge, as only recent progresses enabled the fabrication of efficient tunable nano-antennas at near infrared and visible frequencies. Here we report on a new type of rectenna based on plasmonic carrier generation. The proposed rectifying structure consists of a broadly resonant gold conical nano-tip antenna in contact with a metal-oxide/metal sample surface, forming a point-contact tunneling diode. The nano-sized antenna apex, designed to maximize the Surface Plasmon Polaritons (SPPs) damping, allows for an efficient power conversion from the light field into excited charges above the Fermi level, the latter ones collectable from the point-contact location through an electronic tunneling process. We demonstrated rectification operation at 280 THz with a power conversion efficiency one order of magnitude higher than the state-of-the-art which we attribute to efficient plasmonic carrier generation and collection.
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