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This paper demonstrates that the efficiency of InGaN-based light-emitting diodes with nano-post patterned sapphire substrates is superior to that with nano-hole patterned sapphire substrates under the same nano-scale feature owing to reduced quantum-confined stark effect.
We studied acoustic breathing modes of GaN nanorods on silicon substrates by ultrafast acoustic phonon spectroscopy. This technique could be utilized to nondestructively inspect uniformity of nanorods within the area of optical spot.
The radiation pattern of plasmon-based optical Yagi-Uda antenna was measured in a quasi-homogeneous medium realized by immersing the antenna in a liquid. The directional gain of the 5-element antenna was found to be about 3.7, consistently with the theoretical prediction.
We have designed, fabricated, and characterized novel p-n junction photodetectors based on macroscopic single-wall carbon nanotube films. A broadband responsivity up to ∼ 1 V/W was observed at the junction region. By controlling for substrate and doping levels, we determined that the mechanism is the photothermoelectric effect, which is supported by a theoretical model.
We investigate-light trapping in thin-film crystalline silicon solar cells with rough interfaces and engineered disordered photonic structures. The general aspects of the optical properties are discussed, demonstrating broad band absorption close to the Lambertian limit.
Silicon nanostructures are used for efficiency enhancement in Silicon solar cells. A 2 μm thick solar cell with silicon nanostructures on the front and back surfaces show photocurrent of 26.7 mA/cm2 (77% of the Yablonovitch limit).
Core-multi-shell InP/AlInP nanowire-array solar cells were fabricated using catalyst-free selective-area metal-organic vapor phase epitaxy. The wider-bandgap outer shell layer passivates InP nanowires effectively, increasing the short-circuit current density and conversion efficiency to 6.35% under AM1.5G.
We demonstrate lateral position control of nitrogen-vacancy centers doped near the surface of diamond substrate using micropatterned substrate for nitrogen-doped isotopically-enriched chemical vapor deposition. We confirm the spatially-selective doping of NV centers on etched area. We also found the nitrogen-vacancy creation efficiency at the etched area is much higher than that at the non-etched...
We report a metamorphic GaSb-based laterally coupled distributed-feedback laser grown on a GaAs substrate that operates continuous wave at room temperature with a total output power of 40 mW.
We demonstrate transferring 2cm × 2cm unpatterned nanomembrane onto glass substrates. A photonic crystal waveguide is patterned together with subwavelength grating couplers on the transferred nanomembrane. Group index up to 26.5 is experimentally demonstrated.
We fabricate a large area (3 × 3 cm2) polydimethylsiloxane-based substrate for surface-enhanced Raman scattering by combining femtosecond laser microstructuring and soft lithography techniques. The substrate exhibits broadband absorption in the region of 350–1000 nm and reproducible enhancement factor ∼107.
We fabricated an electrically tunable metamaterial based on twisted nematics liquid crystal cell, where polarization dependent reflectance of the metamaterial can be controlled via applied voltage. When the metamaterial-twisted nematics liquid crystal cell is driven with a voltage above the threshold, optical reflection of the cell has changed. Our result provides the possibility of tuning the frequency...
Room-temperature, narrow-linewidth terahertz quantum cascade laser sources based on intracavity Cherenkov difference-frequency generation with emission at 3.5 THz, nearly 60μW power output, and conversion efficiency of approximately 0.55 mW/W2 are reported.
We demonstrate a multilayer anti-reflective conformal coating for polycarbonate substrates, using a a polymer nanocomposite, fabricated by resonant infrared pulsed laser evaporation. The coating has 97% transmission, and less than 0.6% reflectivity over the visible spectrum.
Ultrashort laser pulses can be used to directly join transparent substrates by localized melting and resolidification without any intermediate layers. I review recent advance of welding and joining of glass substrates with ultrashort laser pulses.
A terahertz sub-surface scanner is introduced that utilizes reflection mode non-contact interrogation of surfaces and interior layers of composite substrates with resolution of ∼1 nm. Quantitative measurements are done by implementing a modified Beer-Lambert's law.
Using ultrafast optical-pump terahertz-probe spectroscopy, we measure the low-temperature electronic cooling in multilayer epitaxial graphene and develop a theory of hot-carrier equilibration based on interlayer energy transfer via screened Coulomb interactions.
Liquid crystal polarizers and waveplates are an enabling technology for large fusion lasers. While damage and replacement rates of liquid crystal optics remain remarkably low, degradation in polarizer performance has been noted and studied.
Monolithic meter-size diffraction gratings are required to improve kilojoule, petawatt laser-system performance. A deformable-grating-based pulse compressor with optimized actuator positions is presented to correct the spatial and temporal aberrations induced by grating wavefront errors.
SiGe/Si quantum-well nanomembranes, where stress due to lattice mismatch is relaxed via elastic strain sharing rather than defect formation, are developed and their potential for far-infrared intersubband device applications is demonstrated.
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