Room temperature operation of germanium-silicon single-photon avalanche diode.

The ability to detect single photons has led to the advancement of numerous research fields. Although various types of single-photon detector have been developed, because of two main factors-that is, (1) the need for operating at cryogenic temperature and (2) the incompatibility with complementary metal-oxide-semiconductor (CMOS) fabrication processes-so far, to our knowledge, only Si-based single-photon avalanche diode (SPAD) has gained mainstream success and has been used in consumer electronics. With the growing demand to shift the operation wavelength from near-infrared to short-wavelength infrared (SWIR) for better safety and performance, an alternative solution is required because Si has negligible optical absorption for wavelengths beyond 1 µm.

Design of a Completely Vertical, Polarization-Independent Two-Dimensional Grating Coupler with High Coupling Efficiency.

An efficient optical coupler to transfer the signal between an optical fiber and a silicon waveguide is essential for realizing the applications of silicon photonic integrated circuits such as optical communication and optical sensing. In this paper, we numerically demonstrate a two-dimensional grating coupler based on a silicon-on-insulator platform to obtain completely vertical and polarization-independent couplings, which potentially ease the difficulty of packaging and measurement of photonic integrated circuits. To mitigate the coupling loss induced by the second-order diffraction, two corner mirrors are respectively placed at the two orthogonal ends of the two-dimensional grating coupler to create appropriate interference conditions.

Fitnesser's Intrinsic Motivations of Green Eating: An Integration of Theory of Planned Behavior and Hedonic-Motivation System Adoption Model.

Global climate change arouses people's attention to environmental protection and, therefore, changes consumption habits. Food overconsumption not only produces extra waste but also pollutes the environment. Therefore, it is important to understand the factors that motivate people to eat green, an eco-friendly way to consume food.

Surface plasmon coupling with radiating dipole for enhancing the emission efficiency of a light-emitting diode.

The experimental demonstrations of light-emitting diode (LED) fabrication with surface plasmon (SP) coupling with the radiating dipoles in its quantum wells are first reviewed. The SP coupling with a radiating dipole can create an alternative emission channel through SP radiation for enhancing the effective internal quantum efficiency when the intrinsic non-radiative recombination rate is high, reducing the external quantum efficiency droop effect at high current injection levels, and producing partially polarized LED output by inducing polarization-sensitive SP for coupling. Then, we report the theoretical and numerical study results of SP-dipole coupling based on a simple coupling model between a radiating dipole and the SP induced on a nearby Ag nanoparticle (NP).

Fabrication of sphere-like Au nanoparticles on substrate with laser irradiation and their polarized localized surface plasmon behaviors.

The fabrications of sphere-like Au nanoparticles (NPs) on sapphire, GaN, and SiO(2) substrates through the irradiation of a few pulses of 266-nm laser onto Au thin films deposited on the substrates are demonstrated. The top-view diameter, contact angle on substrate, surface population density, and surface coverage percentage of the NPs can be controlled by the Au thin film thickness, laser energy density, substrate choice, and the gas or liquid, in which the Au thin film is immersed during laser irradiation. Optical transmission measurements show clear in-plane and out-of-plane localized surface plasmon resonance (LSPR) features, including the air resonance feature dictated by the gas or liquid immersing the NPs during transmission measurement, the in-plane substrate resonance feature controlled by the substrate material and the contact angle, and the out-of-plane resonance feature, which is strongly influenced also by the substrate material and the contact angle.

Effective energy coupling and preservation in a surface plasmon-light emitter coupling system on a metal nanostructure.

The simulation results of the coupling of a radiation dipole with a surface plasmon (SP), which is induced on a metal/dielectric interface of a single groove (SG) plus a grating structure, are demonstrated. With the SG structure, the dipole can effectively couple energy into an SP feature, which has a mixed nature of localized surface plasmon (LSP) and surface plasmon polariton (SPP). The SPP energy is confined by a grating structure with a well designed grating period and position.

Localized surface plasmon-induced emission enhancement of a green light-emitting diode.

The output enhancement of a green InGaN/GaN quantum-well (QW) light-emitting diode (LED) through the coupling of a QW with localized surface plasmons (LSPs), which are generated on Ag nanostructures on the top of the device, is demonstrated. The suitable Ag nanostructures for generating LSPs of resonance energies around the LED wavelength are formed by controlling the Ag deposition thickness and the post-thermal-annealing condition. With a 20 mA current injected onto the LED, enhancements of up to 150% in electroluminescence peak intensity and of 120% in integrated intensity are observed.

Formation of various metal nanostructures with thermal annealing to control the effective coupling energy between a surface plasmon and an InGaN/GaN quantum well.

We demonstrate the variations of the photoluminescence (PL) spectral peak position and intensity through the surface plasmon (SP) coupling with an InGaN/GaN quantum well (QW) by forming Ag nanostructures of different scale sizes on the QW structure with thermal annealing. By transferring an Ag thin film into a nanoisland structure, we can not only enhance the PL intensity, but also adjust the SP dispersion relation and hence red-shift the effective QW emission wavelength. Such an emission spectrum control can be realized by initially coating Ag films of different thicknesses.

Ultrafast pump-probe spectroscopy in the UV-blue range with an extremely broad probe spectrum for the carrier relaxation study in an InGaN thin film with indium-rich nano-clusters.

We implement an extremely broad second-harmonic spectrum of about 90 nm in width based on a 7-fs mode-locked Ti:sapphire laser. This broadband second-harmonic signal is used as the probe in a non-degenerate pump-probe experiment to investigate the ultrafast carrier dynamics in wide band-gap semiconductors. To properly calibrate the pump-probe data, the time delays between the pump of a particular wavelength and the probes of various spectral portions are determined through the interferometry measurement and the dispersion calculation.

Non-degenerate fs pump-probe study on InGaN with multi-wavelength second-harmonic generation.

Non-degenerate fs pump-probe experiments in the UV-visible range for ultrafast carrier dynamics study of InGaN with adjustable pump and probe photon energies are implemented with simultaneously multiwavelength second-harmonic generation (SHG) of a 10 fs Ti:sapphire laser. The multi-wavelength SHG is realized with two beta-barium borate crystals of different cutting angles. The full-widths at half-maximum of the SHG pulses are around 150 fs, which are obtained from the cross-correlation measurement with a reverse-biased 280-nm light-emitting diode as the twophoton absorption photo-detector.