Lasing Emission from Soft Photonic Crystals for Pressure and Position Sensing.

In this report, we introduce a 1D photonic crystal (PhC) nanocavity with waveguide-like strain amplifiers within a soft polydimethylsiloxane substrate, presenting it as a potential candidate for highly sensitive pressure and position optical sensors. Due to its substantial optical wavelength response to uniform pressure, laser emission from this nanocavity enables the detection of a minimum applied uniform pressure of 1.6‱ in experiments.

Enhancing on/off ratio of a dielectric-loaded plasmonic logic gate with an amplitude modulator.

Plasmonic waveguides allow focusing, guiding, and manipulating light at the nanoscale and promise the miniaturization of functional optical nanocircuits. Dielectric-loaded plasmonic (DLP) waveguides and logic gates have drawn attention because of their relatively low loss, easy fabrication, and good compatibility with gain and active tunable materials. However, the rather low on/off ratio of DLP logic gates remains the main challenge.

Dynamic single microparticle manipulation in the far-field region using plasmonic vortex lens multiple arms with a circular groove.

Recent development of particle manipulation has led to high demand for dynamic optical tweezer structures. However, confining and rotating a single microparticle in the far-field region with a uniform potential distribution remains a complicated task. A plasmonic vortex lens (PVL) has been proven to easily rotate the dielectric particle owing to its effect on orbital angular momentum (OAM).

Ultra-compact Archimedes spiral plasmonic lens with a circular groove for low power optical trapping in the far-field region.

Particle levitation is crucial in optical trapping considering contamination and alteration of the character of the particle due to physical contact with the structure. A strong field gradient along the optical axis is required in this case. To manipulate the particle at a distance from the surface, we propose an Archimedes spiral plasmonic lens with a circular groove (CG-ASPL).

Layered Graphene Growth Directly on Sapphire Substrates for Applications.

Layer-by-layer graphene growth is demonstrated by repeating CVD growth cycles directly on sapphire substrates. Improved field-effect mobility values are observed for the bottom-gate transistors fabricated by using the bilayer graphene channel, which indicates an improved crystallinity is obtained after the second CVD growth cycle. Despite the poor wettability of copper on graphene surfaces, graphene may act as a thin and effective diffusion barrier for copper atoms.

Advanced Atomic Layer Deposition Technologies for Micro-LEDs and VCSELs.

In recent years, the process requirements of nano-devices have led to the gradual reduction in the scale of semiconductor devices, and the consequent non-negligible sidewall defects caused by etching. Since plasma-enhanced chemical vapor deposition can no longer provide sufficient step coverage, the characteristics of atomic layer deposition ALD technology are used to solve this problem. ALD utilizes self-limiting interactions between the precursor gas and the substrate surface.

Photonic Crystal Polymeric Thin-Film Dye-Lasers for Attachable Strain Sensors.

In this report, using two-dimensional photonic crystals (PhC) and a one-dimensional PhC nano-beam cavity, we realized the development of all-polymeric dye-lasers on a dye-doped, suspended poly-methylmethacrylate film with a wavelength-scale thickness. In addition to the characterization of basic lasing properties, we also evaluated its capacity to serve as an attachable strain sensor. Through experimentation, we confirmed the stable lasing performances of the dye-laser attaching on a rough surface.

MoS with Stable Photoluminescence Enhancement under Stretching via Plasmonic Surface Lattice Resonance.

In this study, by combining a large-area MoS monolayer with silver plasmonic nanostructures in a deformable polydimethylsiloxane substrate, we theoretically and experimentally studied the photoluminescence (PL) enhancement of MoS by surface lattice resonance (SLR) modes of different silver plasmonic nanostructures. We also observed the stable PL enhancement of MoS by silver nanodisc arrays under differently applied stretching strains, caused by the mechanical holding effect of the MoS monolayer. We believe the results presented herein can guarantee the possibility of stably enhancing the light emission of transition metal dichalcogenides using SLR modes in a deformable platform.

Highly Efficient and Stable White Light-Emitting Diodes Using Perovskite Quantum Dot Paper.

Perovskite quantum dots (PQDs) are a competitive candidate for next-generation display technologies as a result of their superior photoluminescence, narrow emission, high quantum yield, and color tunability. However, due to poor thermal resistance and instability under high energy radiation, most PQD-based white light-emitting diodes (LEDs) show only modest luminous efficiency of ≈50 lm W and a short lifetime of <100 h. In this study, by incorporating cellulose nanocrystals, a new type of QD film is fabricated: CHNHPbBr PQD paper that features 91% optical absorption, intense green light emission (518 nm), and excellent stability attributed to the complexation effect between the nanocellulose and PQDs.

Design, Modeling, and Fabrication of High-Speed VCSEL with Data Rate up to 50 Gb/s.

We have studied the characteristics of frequency response at 850-nm GaAs high-speed vertical-cavity surface-emitting lasers (VCSELs) with different kinds of oxide aperture sizes and cavity length using the PICS3D simulation program. Using 5-μm oxide aperture sizes, the frequency response behavior can be improved from 18.4 GHz and 15.

Engineering surface lattice resonance of elliptical gold nanodisk array for enhanced strain sensing.

We demonstrate an elliptical gold nanodisk array (GNA) for engineering the spectral profile of surface lattice resonance (SLR). The nanodisk's shape has a great impact on SLR. Small linewidth of 20 nm at an aspect ratio of 1.

Liquid Type Nontoxic Photoluminescent Nanomaterials for High Color Quality White-Light-Emitting Diode.

High-brightness white-light-emitting diodes (w-LEDs) with excellent color quality is demonstrated by using nontoxic nanomaterials. Previously, we have reported the high color quality w-LEDs with heavy-metal phosphor and quantum dots (QDs), which may cause environmental hazards. In the present work, liquid-type white LEDs composed of nontoxic materials, named as graphene and porous silicon quantum dots are fabricated with a high color rendering index (CRI) value gain up to 95.

Efficient modulation of subwavelength focusing via meta-aperture-based plasmonic lens for multifunction applications.

Subwavelength focusing is crucial for many applications in photonics including super-resolution micro/nanoscopy, nanolithography, and optical trapping. However, most nanostructures exhibit poor ability to modulate focusing spot, which makes them hard to achieve ultra-small resolution. Here, we propose three kinds of plasmonic lens (PL) by utilizing different meta-aperture designs for efficient subwavelength focusing modulation.

Thermally Strained Band Gap Engineering of Transition-Metal Dichalcogenide Bilayers with Enhanced Light-Matter Interaction toward Excellent Photodetectors.

Integration of strain engineering of two-dimensional (2D) materials in order to enhance device performance is still a challenge. Here, we successfully demonstrated the thermally strained band gap engineering of transition-metal dichalcogenide bilayers by different thermal expansion coefficients between 2D materials and patterned sapphire structures, where MoS bilayers were chosen as the demonstrated materials. In particular, a blue shift in the band gap of the MoS bilayers can be tunable, displaying an extraordinary capability to drive electrons toward the electrode under the smaller driven bias, and the results were confirmed by simulation.

Compressible 1D photonic crystal nanolasers with wide wavelength tuning.

We propose and demonstrate a tunable photonic crystal nanolaser consisting of 1D periodic nanorods wrapped in deformable polydimethylsiloxane. In addition to low-threshold and long-term lasing stability, the nanolaser also displays reproducible and reliable wavelength tuning with a large tunability of 7.7 nm under 1% compression.

A Comprehensive Study of One-Step Selenization Process for Cu(In Ga )Se Thin Film Solar Cells.

In this work, aiming at developing a rapid and environmental-friendly process for fabricating CuIn Ga Se (CIGS) solar cells, we demonstrated the one-step selenization process by using selenium vapor as the atmospheric gas instead of the commonly used HSe gas. The photoluminescence (PL) characteristics indicate that there exists an optimal location with superior crystalline quality in the CIGS thin films obtained by one-step selenization. The energy dispersive spectroscopy (EDS) reveals that the Ga lateral distribution in the one-step selenized CIGS thin film is intimately correlated to the blue-shifted PL spectra.

Wavelength tunable InGaN/GaN nano-ring LEDs via nano-sphere lithography.

In this research, nano-ring light-emitting diodes (NRLEDs) with different wall width (120 nm, 80 nm and 40 nm) were fabricated by specialized nano-sphere lithography technology. Through the thinned wall, the effective bandgaps of nano-ring LEDs can be precisely tuned by reducing the strain inside the active region. Photoluminescence (PL) and time-resolved PL measurements indicated the lattice-mismatch induced strain inside the active region was relaxed when the wall width is reduced.

Effective optimization and analysis of white LED properties by using nano-honeycomb patterned phosphor film.

This study presents an approach for patterning a polydimethylsiloxane (PDMS) phosphor film with a photonic crystal nano-honeycomb structure on a blue chip package. A phosphor film with a nano-honeycomb structure was patterned and transferred using a nanosphere and used for fabricating remote white light-emitting diodes (w-LEDs). The angular correlated color temperature deviation of the remote phosphor LED could be improved by varying nano-honeycomb structure pitches (450, 750, and 1150 nm).

Optical Properties of Plasmonic Mirror-Image Nanoepsilon.

We propose a novel mirror-image nanoepsilon (MINE) structure to achieve highly localized and enhanced near field at its gap and systematically investigate its plasmonic behaviors. The MINE can be regarded as a combination of two fundamental plasmonic nanostructures: a nanorod dimer and nanoring. By adapting a nanoring surrounding a nanorod dimer structure, the nanorod is regarded as a bridge pulling the charges from the nanoring to the nanorod, which induces stronger plasmon coupling in the gap to boost local near-field enhancement.

Pulsed-laser micropatterned quantum-dot array for white light source.

In this study, a novel photoluminescent quantum dots device with laser-processed microscale patterns has been demonstrated to be used as a white light emitting source. The pulsed laser ablation technique was employed to directly fabricate microscale square holes with nano-ripple structures onto the sapphire substrate of a flip-chip blue light-emitting diode, confining sprayed quantum dots into well-defined areas and eliminating the coffee ring effect. The electroluminescence characterizations showed that the white light emission from the developed photoluminescent quantum-dot light-emitting diode exhibits stable emission at different driving currents.

Plasmonic behaviors of metallic AZO thin film and AZO nanodisk array.

Aluminum-doped zinc oxide (AZO) is well known as transparent conducting material for electro-optical devices, but is rarely used as plasmonic material, particularly on the localized surface plasmon resonance (LSPR) behavior of AZO nanostructure and its plasmonic devices. In this study, we systematically investigate the plasmonic behaviors of AZO thin films and patterned AZO nanostructures with various structural dimensions under different annealing treatments. We find that AZO film can possess highly-tunable, metal-like, and low-loss plasmonic property and the LSPR characteristic of AZO nanostructure is observed in the near-infrared (NIR) region under proper annealing conditions.

Enhanced power conversion efficiency in InGaN-based solar cells via graded composition multiple quantum wells.

This work demonstrates the enhanced power conversion efficiency (PCE) in InGaN/GaN multiple quantum well (MQWs) solar cells with gradually decreasing indium composition in quantum wells (GQWs) toward p-GaN as absorber. The GQW can improve the fill factor from 42% to 62% and enhance the short current density from 0.8 mA/cm to 0.

Bioceramic Resonance Effect on Meridian Channels: A Pilot Study.

Bioceramic is a kind of material which emits nonionizing radiation and luminescence, induced by visible light. Bioceramic also facilitates the breakup of large clusters of water molecules by weakening hydrogen bonds. Hydrogen bond weakening, which allows water molecules to act in diverse ways under different conditions, is one of the key mechanisms underlying the effects of Bioceramic on biophysical and physical-chemical processes.