Half-Wave Dipolar Metal-Semiconductor Laser

Nano-scale lasers harnessing metallic plasmons hold promise across physical sciences and industrial applications. Plasmons are categorized as surface plasmon polaritons (SPP) and localized surface plasmons (LSP). While SPP has gained popularity for nano-lasers by fitting a few cycles of SPP waves into resonators, achieving LSP lasing in single nanoparticles remains an elusive goal. Here, we highlight the equivalence of LSP and SPP within resonant systems and present lasers oscillating in the lowest-order LSP or, equivalently, half-cycle SPP. This diffraction-limited dipolar emitter is realized through strong coupling of plasmonic oscillation in gold and dielectric resonance in high-gain III-V semiconductor in the near infrared away from surface plasmon frequencies. The resulting single-mode stimulated emission peak exhibits linewidth Q factors over 50 at room temperature, with wide tunability spanning from 1190 to 1460 nm determined by resonator sizes ranging from 190 to 280 nm. A semiconductor laser model elucidates the temporal and spectral buildup dynamics under optical pumping. Notably, linewidth Q values surpassing 250 are attained from higher-order, isolated laser particles within live biological cells. These results offer fresh perspectives in nanophotonics and indicate promising opportunities for multiplexed biological applications

Measuring mechanical anisotropy of the cornea with Brillouin microscopy

Load-bearing tissues are typically fortified by networks of protein fibers, often with preferential orientations. This fiber structure imparts the tissues with direction-dependent mechanical properties optimized to support specific external loads. To accurately model and predict tissues' mechanical response, it is essential to characterize the anisotropy on a microstructural scale. Previously, it has been difficult to measure the mechanical properties of intact tissues noninvasively. Here, we use Brillouin optical microscopy to visualize and quantify the anisotropic mechanical properties of corneal tissues at different length scales. We derive the stiffness tensor for a lamellar network of collagen fibrils and use angle-resolved Brillouin measurements to determine the longitudinal stiffness coefficients (longitudinal moduli) describing the ex vivo porcine cornea as a transverse isotropic material. Lastly, we observe significant mechanical anisotropy of the human cornea in vivo, highlighting the potential for clinical applications of off-axis Brillouin microscopy

Photonic Crystal Flakes

Photonic crystals (PCs) have been traditionally produced on rigid substrates. Here, we report the development of free-standing one-dimensional (1D) slanted PC flakes. A single pulse of a 5 ns Nd:YAG laser (λ = 532 nm, 350 mJ) was used to organize silver nanoparticles (10–50 nm) into multilayer gratings embedded in ∼10 μm poly­(2-hydroxyethyl methacrylate-<i>co</i>-methacrylic acid) hydrogel films. The 1D PC flakes had narrow-band diffraction peak at ∼510 nm. Ionization of the carboxylic acid groups in the hydrogel produced Donnan osmotic pressure and modulated the Bragg peak. In response to pH (4–7), the PC flakes shifted their diffraction wavelength from 500 to 620 nm, exhibiting 0.1 pH unit sensitivity. The color changes were visible to the eye in the entire visible spectrum. The optical characteristics of the 1D PC flakes were also analyzed by finite element method simulations. Free-standing PC flakes may have application in spray deposition of functional materials

Supplementary document for In situ measurement of stiffness increase in posterior sclera after UV-riboflavin crosslinking by optical coherence elastography - 5997340.pdf

This document provides additional details related to the paper "In situ measurement of stiffness increase in posterior sclera after UV-riboflavin crosslinking by optical coherence elastography"

Cross-sectional UHR-SD-OCT image stack (XZ, full resolution) of porcine left bundle branch fibers

Cross-sectional UHR-SD-OCT image stack (XZ, full resolution) of an area of the left ventricular outlet septum in a porcine heart immediately below the membranous septum and below the aortic valve (transition from membranous septum to conduction tissue in left bundle branch

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High-speed synthesis of bead barcodes in droplet microfluidic

UHR-SD-OCT image stack (YZ, resliced) of porcine left bundle branch fibers

Cross-sectional UHR-SD-OCT image stack (YZ, resliced, downsampled due to constraints on video file size) of an area of the left ventricular outlet septum in a porcine heart immediately below the membranous septum and below the aortic valve (transition from membranous septum to conduction tissue in left bundle branch

Supplementary document for Droplet microfluidic generation of a million optical microparticle barcodes - 5435319.pdf

Supplemental Documen

Cross-sectional UHR-SD-OCT image stack (XZ) of porcine left bundle branch fibers

Cross-sectional UHR-SD-OCT image stack (XZ, downsampled due to constraints on video file size) of an area of the left ventricular outlet septum in a porcine heart immediately below the membranous septum and below the aortic valve (transition from membranous septum to conduction tissue in left bundle branch

Ultrasmall InGa(As)P dielectric and plasmonic nanolasers

Nanolasers have great potential as both on-chip light sources and optical barcoding particles. We demonstrate ultrasmall InGaP and InGaAsP disk lasers with diameters down to 360 nm (198 nm in height) in the red spectral range. Optically pumped, room-temperature, single-mode lasing was achieved from both disk-on-pillar and isolated particles. When isolated disks were placed on gold, plasmon polariton lasing was obtained with Purcell-enhanced stimulated emission. UV lithography and plasma ashing enabled the fabrication of nanodisks on a wafer-scale, with intended random size variation. Silica-coated nanodisk particles generated stable sub-nanometer spectra from within biological cells across an 80 nm bandwidth from 635 to 715 nm