Spatially-coded Fourier ptychography: flexible and detachable coded thin films for quantitative phase imaging with uniform phase transfer characteristics.

Fourier ptychography (FP) is an enabling imaging technique that produces high-resolution complex-valued images with extended field coverages. However, when FP images a phase object with any specific spatial frequency, the captured images contain only constant values, rendering the recovery of the corresponding linear phase ramp impossible. This challenge is not unique to FP but also affects other common microscopy techniques -- a rather counterintuitive outcome given their widespread use in phase imaging.

Noninvasive Injectable Optical Nanosensor-Hydrogel Hybrids Detect Doxorubicin in Living Mice.

While the tissue-transparent fluorescence of single-walled carbon nanotubes (SWCNTs) imparts substantial potential for use in non-invasive biosensors, development of non-invasive systems is yet to be realized. Here, we investigated the functionality of a SWCNT-based nanosensor in several injectable SWCNT-hydrogel systems, ultimately finding SWCNT encapsulation in a sulfonated methylcellulose hydrogel optimal for detection of ions, small molecules, and proteins. We found that the hydrogel system and nanosensor signal were stable for several weeks in live mice.

Plasmonic dielectric antennas for hybrid optical nanotweezing and optothermoelectric manipulation of single nanosized extracellular vesicles.

This paper showcases an experimental demonstration of near-field optical trapping and dynamic manipulation of an individual extracellular vesicle. This is accomplished through the utilization of a plasmonic dielectric nanoantenna designed to support an optical anapole state-a non-radiating optical state resulting from the destructive interference between electric and toroidal dipoles in the far-field, leading to robust near-field enhancement. To further enhance the field intensity associated with the optical anapole state, a plasmonic mirror is incorporated, thereby boosting trapping capabilities.

Aggregation-Induced Stimulated Emission of 100% Dye Microspheres.

Dyes with aggregation-induced emission (AIE) properties have gained interests due to their bright luminescence in solid-state aggregates. While fluorescence from AIE dyes have been widely exploited, relatively little is known about aggregation-induced emission. Here, we investigated stimulated emission of tetraphenylethene (TPE)-based organoboron AIE dyes, TPEQBN, in thin films and in microcavity lasers.

Pyramidal hyperbolic metasurfaces enhance spontaneous emission of nitrogen-vacancy centers in nanodiamond.

Nitrogen-vacancy (NV) centers in nanodiamond hold great promise for creating superior biological labels and quantum sensing methods. Yet, inefficient photon generation and extraction from excited NV centers restricts the achievable sensitivity and temporal resolution. Herein, we report an entirely complementary route featuring pyramidal hyperbolic metasurface to modify the spontaneous emission of NV centers.

Bio-inspired Compact, High-resolution Snapshot Hyperspectral Imaging System with 3D Printed Glass Lightguide Array.

To address the major challenges to obtain high spatial resolution in snapshot hyperspectral imaging, 3D printed glass lightguide array has been developed to sample the intermediate image in high spatial resolution and redistribute the pixels in the output end to achieve high spectral resolution. Curved 3D printed lightguide array can significantly simplify the snapshot hyperspectral imaging system, achieve better imaging performance, and reduce the system complexity and cost. We have developed two-photon polymerization process to print glass lightguide array, and demonstrated the system performance with biological samples.

Near-Unity Superradiant Emission from Delocalized Frenkel Excitons in a Two-Dimensional Supramolecular Assembly.

We demonstrate three general effective strategies to mitigate non-radiative losses in the superradiant emission from supramolecular assemblies. We focus on J-aggregates of 5,5',6,6'-tetrachloro-1,1'-diethyl-3,3'-di(4-sulfobutyl)-benzimidazolocarbocyanine (TDBC) and elucidate the nature of their nonradiative processes. We show that self-annealing at room temperature, photo-brightening, and the purification of the dye monomers all lead to substantial increases in emission quantum yields (QYs) and a concomitant lengthening of the emission lifetime, with purification of the monomers having the largest effect.

Nonlinear Strong Coupling by Second-Harmonic Generation Enhancement in Plasmonic Nanopatch Antennas.

Enhanced electromagnetic fields within plasmonic nanocavity mode volumes enable multiple significant effects that lead to applications in both the linear and nonlinear optical regimes. In this work, we demonstrate enhanced second harmonic generation from individual plasmonic nanopatch antennas which are formed by separating silver nanocubes from a smooth gold film using a sub-10 nm zinc oxide spacer layer. When the nanopatch antennas are excited at their fundamental plasmon frequency, a 10-fold increase in the intensity of the second harmonic generation wave is observed.

True FRET-based sensing of pH via Separation of FRET and Photon Reabsorption.

Förster Resonance Energy Transfer (FRET)-based devices have been extensively researched as potential biosensors due to their highly localized responsivity. In particular, dye-conjugated upconverting nanoparticles (UCNPs) are among the most promising FRET-based sensor candidates. UCNPs have a multi-modal emission profile that allows for ratiometric sensing, and by conjugating a biosensitive dye to their surface, this profile can be used to measure localized variations in biological parameters.

Plasmonic Nanotweezers and Nanosensors for Point-of-Care Applications.

The capabilities of manipulating and analyzing biological cells, bacteria, viruses, DNAs, and proteins at high resolution are significant in understanding biology and enabling early disease diagnosis. We discuss progress in developments and applications of plasmonic nanotweezers and nanosensors where the plasmon-enhanced light-matter interactions at the nanoscale improve the optical manipulation and analysis of biological objects. Selected examples are presented to illustrate their design and working principles.

Hydrogel-based diffractive optical elements (hDOEs) using rapid digital photopatterning.

Hydrogels, due to their optical transparency and biocompatibility, have emerged as an excellent alternative to conventional optical materials for biomedical applications. Advances in microfabrication techniques have helped convert conventional hydrogels into optically functional materials such as hydrogel-based diffraction optical elements (hDOEs). However, key challenges related to device customization and ease/speed of fabrication need to be addressed to enable widespread utility and acceptance of hDOEs in the field.

Dye Stabilization and Wavelength Tunability in Lasing Fibers Based on DNA.

Lasers based on biological materials are attracting an increasing interest in view of their use in integrated and transient photonics. Deoxyribonucleic acid (DNA) as optical biopolymer in combination with highly emissive dyes has been reported to have excellent potential in this respect. However, achieving miniaturized lasing systems based on solid-state DNA shaped in different geometries to confine and enhance emission is still a challenge, and the physicochemical mechanisms originating fluorescence enhancement are not fully understood.

Aggregation-Induced Emissive and Circularly Polarized Homogeneous Sulfono-γ-AApeptide Foldamers.

Through our continuous effort in developing a new class of foldamers, we have both designed and synthesized homogenous sulfono-γ-AApeptides using tetraphenylethylene (TPE) moieties attached to the backbone as luminogenic sidechains. Based on previous crystal structures, we have found that these foldamers adopted a left-handed 4-helix. Due to the constraint of the helical scaffold, the rotation of the TPE moieties were restricted, leading to fluorescent emissive properties with high quantum yields not only at the aggregate state but also in solution.

Quaternary Ammonium Salt Based NIR-II Probes for Imaging.

Traditional luminescent materials including fluorescent probes suffer from notorious aggregation-caused quenching (ACQ) in aqueous solutions. Although several approaches such as the aggregation-induced emission (AIE) effect have been developed, it remains a significant challenge to identify an effective and efficient strategy to resolve this issue. Herein, quaternary ammonium salts and as a novel class of bright near infrared window II (NIR-II, 1,000 - 1,700 nm) probes were designed and synthesized, and the twisted intramolecular charge transfer (TICT) formation at the excited state can be effectively suppressed for the newly designed probes.

Biological Photonic Crystal-Enhanced Plasmonic Mesocapsules: Approaching Single-Molecule Optofluidic-SERS Sensing.

Surface-enhanced Raman scattering (SERS) sensing in microfluidic devices, namely optofluidic-SERS, suffers an intrinsic trade-off between mass transport and hot spot density, both of which are required for ultra-sensitive detection. To overcome this compromise, photonic crystal-enhanced plasmonic mesocapsules are synthesized, utilizing diatom biosilica decorated with in-situ growth silver nanoparticles (Ag NPs). In our optofluidic-SERS testing, 100× higher enhancement factors and greater than 1,000× better detection limit were achieved compared with traditional colloidal Ag NPs, the improvement of which is attributed to unique properties of the mesocapsules.

Seeing the Unseen: The Role of Liquid Crystals in Gas-Sensing Technologies.

Fast, real-time detection of gases and volatile organic compounds (VOCs) is an emerging research field relevant to most aspects of modern society, from households to health facilities, industrial units, and military environments. Sensor features such as high sensitivity, selectivity, fast response, and low energy consumption are essential. Liquid crystal (LC)-based sensors fulfill these requirements due to their chemical diversity, inherent self-assembly potential, and reversible molecular order, resulting in tunable stimuliresponsive soft materials.

Pairing Toroidal and Magnetic Dipole Resonances in Elliptic Dielectric Rod Metasurfaces for Reconfigurable Wavefront Manipulation in Reflection.

A novel approach for reconfigurable wavefront manipulation with gradient metasurfaces based on permittivity-modulated elliptic dielectric rods is proposed. It is shown that the required 2π phase span in the local electromagnetic response of the metasurface can be achieved by pairing the lowest magnetic dipole Mie resonance with a toroidal dipole Mie resonance, instead of using the lowest two Mie resonances corresponding to fundamental electric and magnetic dipole resonances as customarily exercised. This approach allows for the precise matching of both the resonance frequencies and quality factors.

Additive Manufacturing: Applications and Directions in Photonics and Optoelectronics.

The combination of materials with targeted optical properties and of complex, 3D architectures, which can be nowadays obtained by additive manufacturing, opens unprecedented opportunities for developing new integrated systems in photonics and optoelectronics. The recent progress in additive technologies for processing optical materials is here presented, with emphasis on accessible geometries, achievable spatial resolution, and requirements for printable optical materials. Relevant examples of photonic and optoelectronic devices fabricated by 3D printing are shown, which include light-emitting diodes, lasers, waveguides, optical sensors, photonic crystals and metamaterials, and micro-optical components.

Hybrid Laser Printing of 3D, Multiscale, Multimaterial Hydrogel Structures.

Fabrication of multiscale, multi-material three-dimensional (3D) structures at high resolution is difficult using current technologies. This is especially significant when working with hydrated and mechanically weak hydrogel materials. In this work, a new hybrid laser printing (HLP) technology is reported to print complex, multiscale, multimaterial, 3D hydrogel structures with microscale resolution.

Programmable Microfluidic Synthesis of Over One Thousand Uniquely Identifiable Spectral Codes.

Encoded microparticles have become a powerful tool for a wide array of applications, including high-throughput sample tracking and massively parallel biological multiplexing. Spectral encoding, where particles are encoded with distinct luminescence spectra, provides a particularly appealing encoding strategy because of the ease of reading codes and assay flexibility. To date, spectral encoding has been limited in the number of codes that can be accurately resolved.

Enhancing the Angular Sensitivity of Plasmonic Sensors Using Hyperbolic Metamaterials.

Surface plasmon resonance (SPR) sensors operate mainly on prism and grating coupling techniques, with spectral and angular scans being the two major interrogation schemes. Among them, the angular scan technique has several advantages including higher measurement precision owing to its higher signal-to-noise ratio. The currently available SPR sensor arrangements provide a maximum angular sensitivity of 500°-600° per RIU.

Active Polymer Microfiber with Controlled Polarization Sensitivity.

of an active polymer microfiber has been proposed and realized with the electrospun method. The fluorescence intensity guiding through this active polymer microfiber shows high sensitivity to the polarization state of the excitation light. What is more, the fluorescence out-coupled from tip of the microfiber can be of designed polarization state.

Planar Photonic Crystal Biosensor for Quantitative Label-Free Cell Attachment Microscopy.

In this study, a planar-surface photonic crystal (PC) biosensor for quantitative, kinetic, label-free imaging of cell-surface interactions is demonstrated. The planar biosensor surface eliminates external stimuli to the cells caused by substrate topography to more accurately reflect smooth surface environment encountered by many cell types in vitro. Here, a fabrication approach that combines nanoreplica molding and a horizontal dipping process is used to planarize the surface of the PC biosensor.