An analysis of the terahertz (THz) optical force acting on a dielectric nanoparticle in the vicinity of a graphene monolayer is presented here. selleck A graphene sheet, when positioned on a dielectric planar substrate, facilitates the excitation of a well-localized surface plasmon (SP) by a nano-sized scatterer, confined to the dielectric surface. The particle can endure significant pulling forces under a wide range of conditions, arising from the interplay of linear momentum conservation and self-action forces. Particle shape and orientation are demonstrably key factors influencing the pulling force intensity, as indicated by our results. Applications involving biospecimen manipulation in the terahertz region become feasible with the development of a novel plasmonic tweezer, driven by the low heat dissipation of graphene SPs.

Our report details the first observation, to our knowledge, of random lasing in neodymium-doped alumina lead-germanate (GPA) glass powder. Using a conventional melt-quenching technique at room temperature, the samples were fabricated, and x-ray diffraction analysis verified the amorphous nature of the resulting glass. To obtain powders with an average grain size of about 2 micrometers, glass samples were ground and then separated by sedimentation using isopropyl alcohol, thereby removing the larger particles. An optical parametric oscillator, precisely set at 808 nm and in resonance with the neodymium ion (Nd³⁺) transition 4I9/2 → 4F5/2 → 4H9/2, was instrumental in exciting the sample. While one might expect a negative consequence, the use of high neodymium oxide content (10% wt. N d 2 O 3) in GPA glass, which induces luminescence concentration quenching (LCQ), is not disadvantageous; the speed of stimulated emission (RL emission) surpasses the nonradiative energy transfer among N d 3+ ions responsible for quenching.

To understand the luminescence of skim milk, diverse protein content samples were examined, after the incorporation of rhodamine B. The 532 nm-tuned nanosecond laser's excitation of the samples produced emission classified as a random laser. Its features were examined in relation to the quantity of protein aggregates. The protein content was found by the results to be linearly correlated with the random laser peak intensity. The intensity of random laser emission forms the basis of a rapid photonic method, detailed in this paper, to assess protein content in skim milk.

Three laser resonators emitting at 1053 nm, pumped by diodes integrated with volume Bragg gratings at 797 nm, are presented, achieving, to the best of our knowledge, the highest reported efficiencies for Nd:YLF in a four-level system. A 14 kW peak pump power diode stack pumps the crystal, yielding a 880 W peak output power.

Sensor interrogation via reflectometry traces, using signal processing and feature extraction, remains under-researched. Signal processing approaches derived from audio processing are applied in this study to analyze traces from experiments involving an optical time-domain reflectometer and a long-period grating in diverse external media. By using the reflectometry trace's characteristics, this analysis highlights the capability of correctly identifying the external medium. The features derived from the traces produced robust classifiers, among which one exhibited an impressive 100% classification accuracy for this particular dataset. This technology's deployment is suitable for circumstances demanding the nondestructive distinction of a predefined set of gases or liquids.

Dynamically stable resonators are well-suited for ring lasers, exhibiting a stability interval twice as large as linear resonators and a decrease in misalignment sensitivity with increasing pump power. Unfortunately, practical design guidance is scarce in the existing literature. Nd:YAG ring resonators, side-pumped by diodes, are capable of delivering single-frequency operation. Although the single-frequency laser demonstrated excellent output characteristics, the resonator's significant length was incompatible with the design of a compact device with low misalignment sensitivity and greater longitudinal mode spacing, essential for improving the single-frequency output. From previously developed equations, enabling the facile design of a dynamically stable ring resonator, we analyze the construction of an analogous ring resonator, aiming to create a shorter resonator with the same stability parameter zone. The investigation of the symmetric resonator, encompassing a pair of lenses, revealed the conditions needed for the construction of the shortest possible resonator.

Trivalent neodymium ions (Nd³⁺) at 1064 nm, with their excitation independent of ground state transitions, have been the subject of recent research, revealing an unprecedented manifestation of a photon avalanche-like (PA-like) mechanism, where temperature change is essential. N d A l 3(B O 3)4 particles were selected for this initial experiment to confirm the principle. An outcome of the PA-like mechanism is the substantial boost in excitation photon absorption, generating light emission that spans the visible and near-infrared spectrum. In the preliminary study, the temperature elevation was due to inherent non-radiative relaxations from the N d 3+ ions, with a PA-like mechanism initiated at a set excitation power limit (Pth). Following this, an external heat source was employed to activate the PA-like mechanism, maintaining excitation power below Pth at ambient temperature. By means of an auxiliary 808 nm beam, resonant with the Nd³⁺ ground-state transition 4I9/2 → 4F5/2 → 4H9/2, we demonstrate the activation of the PA-like mechanism. This constitutes the first reported instance, to the best of our knowledge, of an optically switched PA, and the underlying physical principle involves additional heating of the particles due to phonon emissions from the Nd³⁺ relaxation routes when excited by an 808 nm beam. selleck The presented results suggest potential uses for controlled heating and remote temperature sensing techniques.

Fluoride and N d 3+ were incorporated into Lithium-boron-aluminum (LBA) glass compositions, resulting in the production of these materials. The absorption spectra served as the basis for computing the Judd-Ofelt intensity parameters, 24, 6, and the spectroscopic quality factors. Utilizing the luminescence intensity ratio (LIR) approach, we investigated the potential of near-infrared temperature-dependent luminescence for optical thermometry applications. Three LIR schemes were proposed, resulting in relative sensitivity values reaching up to 357006% K⁻¹. Spectroscopic quality factors were derived from the temperature-dependent luminescence measurements. The investigation's results point towards N d 3+-doped LBA glasses as having potential in both optical thermometry and as gain mediums for solid-state lasers.

This study sought to assess the performance of spiral polishing systems in restorative materials, employing optical coherence tomography (OCT). Research investigated how well spiral polishers functioned when utilized on resin and ceramic surfaces. The surface roughness of restorative materials was quantified, and images of the polishing instruments were obtained via optical coherence tomography (OCT) and stereomicroscope observation. A reduction in surface roughness was observed in ceramic and glass-ceramic composite materials polished by a resin-based system uniquely designed for this application, as demonstrated by the p-value being less than 0.01. Variations in surface area were noted across all polishing surfaces, with the exception of the medium-grit polisher employed in ceramic processing (p<0.005). The reliability of OCT and stereomicroscopy image analysis was very high, with inter-observer and intra-observer Kappa scores of 0.94 and 0.96, respectively. OCT's capabilities extended to the evaluation of wear points within spiral polishers.

This paper introduces methods for producing and evaluating biconvex spherical and aspherical lenses, of 25 mm and 50 mm diameters, respectively, manufactured through additive processes using a Formlabs Form 3 stereolithography 3D printer. Prototype post-processing analysis revealed fabrication errors in the radius of curvature, optical power, and focal length, exhibiting a 247% deviation. We showcase the functionality of both the fabricated lenses and our proposed method, proven through eye fundus images taken with an indirect ophthalmoscope and utilizing printed biconvex aspherical prototypes. This method is rapid and cost-effective.

A pressure-sensitive platform, equipped with a series of five macro-bend optical fiber sensors, is demonstrated in this work. The 2020cm system's architecture features sixteen 55cm sensing compartments. The visible spectrum's wavelength-dependent intensity shifts in the array's transmission are the basis of sensing, conveying information about the structure's applied pressure. The process of data analysis involves using principal component analysis to transform spectral data into 12 principal components, capturing 99% of the variance. This process further integrates k-nearest neighbors classification and support vector regression methods. Sensors, fewer in number than the monitored cells, demonstrated a 94% accurate prediction of pressure location, with a mean absolute error of 0.31 kPa within the 374-998 kPa range.

Color constancy is the attribute that makes surface colors appear constant, despite shifts in the illumination spectrum happening over time. The illumination discrimination task (IDT) indicates a lower discrimination threshold for illumination changes towards bluer colors (cooler color temperatures on the daylight chromaticity locus) in typical trichromatic vision. This finding suggests increased stability in scene colors or enhanced color constancy relative to shifts in other color directions. selleck Using a real-world, immersive IDT scenario illuminated by spectrally tunable LED lamps, we contrast the performance of individuals with X-linked color-vision deficiencies (CVDs) to that of normal trichromats. Discriminating illumination changes from a baseline illumination (D65) is assessed in four chromatic directions, approximately parallel and perpendicular to the daylight locus.