Miniaturized quasi-BICs based on a two-dimensional heterostructure to realize a low-threshold nanolaser.

Bound states in the continuum (BICs) have been demonstrated as an effective mechanism to achieve high quality (Q)-factor cavities for nanolasers. However, the development of a compact BIC laser with a low threshold has remained elusive. Here, we numerically report lasing action from symmetry-protected BICs in a two-dimensional heterostructure, which consists of compound gratings with finite cells surrounded by orthogonal distributed Bragg reflectors (DBRs).

Miniaturized guided-mode resonance laser based on a one-dimensional finite heterostructure cavity.

Lasers based on the resonant nanostructures have attracted much attention due to their low threshold and compact dimensions. Guided-mode resonance (GMR) structures have been studied in lasing configurations because of their optical field enhancement and convenient free space excitation. However, the GMR inherently requires a larger footprint and is not suitable for high-density packaging.

Tunable nanolaser based on quasi-BIC in a slanted resonant waveguide grating.

Nanolasers based on quasi-bound states in the continuum (quasi-BIC) have attracted much attention owing to their unique optical properties providing strong light-matter interaction. Although various quasi-BIC lasers have been designed, so far, few efforts have been devoted to their tunability in wavelength. Here we propose an approach to employ quasi-BIC and guided mode in a slanted resonant waveguide grating.

Guided-mode resonance sensors with ultrahigh bulk sensitivity and figure of merit assisted by a metallic layer and structural symmetry-breaking.

We propose a refractive index sensor with both high bulk sensitivity and figure of merit (FOM) that engages the guided-mode resonance (GMR) effect with the assistance of a metallic layer and structural symmetry-breaking in the grating layer. Owing to the existence of the metallic layer, the electric field at resonance can be reflected to the sensing environment, and enhanced bulk sensitivity is realized. Meanwhile, the full width at half maximum of the GMR mode can be decreased by increasing the asymmetrical degree of the grating, thus obtaining a high FOM which benefits the sensing resolution.

Low-threshold lasing behavior based on quasi-bound states in the continuum in a slanted guided-mode resonance nanocavity.

In this study, hybrid resonance modes are obtained when symmetry-breaking is introduced into a guided-mode resonance (GMR) grating, which transforms bound states in the continuum (BICs) into quasi-BICs with a high-quality factor while retaining the intrinsic GMR mode. The structural parameters are modified such that GMR and quasi-BICs resonance occur at the pump and emission wavelengths of the gain medium, respectively. Resonant optical pumping and high-quality nanocavities are utilized simultaneously, and a low-threshold laser is realized.

Enhanced lasing behavior enabled by guided-mode resonance structure embedded with double waveguide layers.

By doping a laser dye into two polyurethane layers in a guided-mode resonance (GMR) structure, we observed that the lasing emission can be enhanced by approximately fivefold. The structure comprises, from top to bottom, a grating layer, four alternating layers of polyurethane and , and a bottom substrate. Two different GMR wavelengths can be generated because of the two films of serving as waveguide layers.

Pyroelectricity and field-induced spin-flop in (4-(Aminomethyl)pyridinium) MnCl · 2HO.

Large single crystals of (4-(Aminomethyl)pyridinium) MnCl · 2HO () were grown by slow evaporation of solution. The crystal structure was solved to be Pī, which belongs to the central symmetric space group. But small pyroelectric current was detected, as well as a ferroelectric hysteresis loop.

Effects of Four Kinds of Oxide Nanoparticles on Proteins in Extracellular Polymeric Substances of Sludge.

Proteins are the most important component in sludge extracellular polymeric substances (EPS) and play a crucial role in the formation of sludge flocs, adsorption performance of sludge, and flocculation ability of sludge. This research is aimed at exploring the changes in proteins in EPS extracted from concentrated sludge after various nanoparticle (NP) treatments. The results showed that the protein content in EPS decreased by 40% after nanoalumina (AlO NPs) treatment but increased at varying degrees after nanoferric oxide (FeO NPs), nanozinc oxide (ZnO NPs), and nanotitanium dioxide (TiO NPs) treatments.

Improving the sensitivity of guided-mode resonance sensors under oblique incidence condition.

We present an investigation on the use of oblique incidence condition to enhance the sensitivity of guided-mode resonance (GMR) sensors. By adjusting the incident angle, the enhancement of GMR sensitivity in non-subwavelength regime can be obtained. The measured results show that the bulk sensitivity of the GMR sensors with period of 809 nm climbs to 177% or 292% as the incident angle increases from 15° to 25° or 35°, respectively.

Non-homogeneous composite GMR structure to realize increased filtering range.

A non-homogeneous composite guided-mode resonant (GMR) filter structure is proposed that avoids the multi-mode resonance effect and increases resonant wavelength tuning range. The composite filter structure is engineered using a combination of a varied-line-spacing (VLS) grating layer with a wedge-shaped waveguide layer. The grating is fabricated by holographic interference lithography (IL), while the wedge-shaped layer is fabricated using masked ion beam etching (MIBE) technology.

Varied-line-spacing switchable holographic grating using polymer-dispersed liquid crystal.

A varied-line-spacing switchable holographic grating is demonstrated through a changeable interference pattern recorded in polymer-dispersed liquid crystal. The pattern is generated by the interference between one plane wave and another cylindrical wave. The line spacing and the period of grating can be controlled by varying the distance between the cylindrical lens and the grating sample and by changing the exposure angle between the two beams.

Tri-color composite volume H-PDLC grating and its application to 3D color autostereoscopic display.

A tri-color composite volume holographic polymer dispersed liquid crystal (H-PDLC) grating and its application to 3-dimensional (3D) color autostereoscopic display are reported in this paper. The composite volume H-PDLC grating consists of three different period volume H-PDLC sub-gratings. The longer period diffracts red light, the medium period diffracts the green light, and the shorter period diffracts the blue light.

Parallel detection experiment of fluorescence confocal microscopy using DMD.

Parallel detection of fluorescence confocal microscopy (PDFCM) system based on Digital Micromirror Device (DMD) is reported in this paper in order to realize simultaneous multi-channel imaging and improve detection speed. DMD is added into PDFCM system, working to take replace of the single traditional pinhole in the confocal system, which divides the laser source into multiple excitation beams. The PDFCM imaging system based on DMD is experimentally set up.

Electro-optical characteristics of holographic polymer dispersed liquid crystal gratings doped with nanosilver.

We report on the synthesis and characteristics of a holographic polymer dispersed liquid crystal (H-PDLC) switchable grating based on nano-Ag particles. The influence of doping different concentrations of nano-Ag on the diffraction efficiency, driving voltage, and response time of the H-PDLC grating is investigated. The best grating characteristics were achieved with 0.