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Photonic crystal fibers were demonstrated as an optimal platform for enhancing the Raman signals to study nanoparticles properties in liquids. Raman was used to analyze stages of low concentrations of ZnO nanoparticles growth in solution.
We demonstrate ultrafast self- and cross-absorption saturation and self-phase modulation based on near-infrared intersubband transitions in GaN/AlN quantum-well waveguides designed to minimize the nonlinear switching energy.
With femtosecond-pulse excitation, two- and three-photon absorption induced ultraviolet lasing with spectral linewidth 0.2-1 nm have been realized under very low excitation threshold from ZnO nanorod arrays at both room and liquid nitrogen temperatures.
An InGaN/GaN thin-film light-emitting diode with the photonic crystal (PhC) on the surface and a TiO2/SiO2 omnidirectional reflector on the bottom was fabricated and found the line-width emission spectrum of 5 nm by the PhC.
We demonstrated CW laser operation of GaN-based VCSELs under current injection at 77 K. CW laser action was achieved at a threshold current of 1.4 mA, emitting at 462 nm with a narrow linewidth of about 0.15 nm.
Tuned by a variable reflective mirror, we achieve 71.2-W free-running and 30-W maximum average power in range of 1866-2107 nm in Tm-doped fiber lasers. Watt-level powers are generated from single crystal and ceramic Cr2+:ZnSe disk lasers.
We report on the study of incorporation of organic thin film semiconductors with GaN to explore new types of photodetector or solar cell application. Photovoltaic effect and photoconductivity gain have been demonstrated using GaN/CuPc and GaN/alpha -NPD hybrid device structure, which offer new opportunities in design of versatile optoelectronic devices.
We present time-resolved photoluminescence on InGaN/GaN multiple-quantum well LEDs grown on nonpolar and semipolar bulk GaN substrates and investigate increasing indium concentrations toward higher power, longer wavelength light emitters.
We fabricated photonic crystal nanocavities to enhance erbium (Er) emission in silicon rich nitride nanocrystals. We observed experimental quality factors of ~6000 and 20-fold enhancement, in agreement with numerical calculations of the Purcell effect.
We have observed resonance-enhanced Stokes and anti-Stokes Raman scattering of coherent picosecond pulses by one as well as two longitudinal-optical phonons in GaN film grown on Si (111) substrate.
We demonstrate the high light-extraction efficiency by using the photoelectrochemical etching technique for forming photonic crystal structures on an InGaN/GaN quantum-well light-emitting diode through phase-mask interference. More than 90% increase of output power is observed.
Optimization studies of InGaN quantum wells light emitting diodes employing SiO2/polystyrene microlens arrays are conducted. The use of microlens arrays leads to increase in light extraction efficiency by 2.7-times, in agreement with simulation.
Effects of 137Cs gamma irradiation on photoluminescent properties of CdSe/ZnS colloidal quantum dots are reported. Optical degradation was evaluated by measuring dependence of photoluminescence intensity on irradiation dose. CdSe/ZnS quantum dots show poor radiation hardness.
InGaN micro-hole-array LEDs (mu-LEDs) with and without oxide-film on it were fabricated. Compared with conventional LED, output power of mu-LEDs without and with oxide film have enhancement of 38% and 82% at 20 mA, respectively.
We have studied the crystal orientation effect on optical anisotropy in InGaN/GaN quantum-well light-emitting diodes. The absolute value of the anisotropy is found to increase rapidly with increasing crystal angle.
Angular and spectral reflectivities of GaN nano-pillar structures are investigated for heights of 350 nm, 550 nm and 720 nm. Calculations based on rigorous coupled-wave analysis show excellent agreement with the measured reflectivities for s- and p-polarizations.
We report on a first successful operation of current-driven GaN photonic-crystal surface-emitting laser, which can operate in blue-violet wavelength regions at room temperature.
We tune the exchange interaction in nanocrystals by manipulating the electron-hole wavefunction overlap under external electric fields and simultaneously probe the electronic structure and rich transient dynamics under strong magnetic fields (8 T).
We perform time-resolved Faraday rotation measurements on colloidal ZnO quantum dots. A biexponential decay of the dephasing time T2* of the electron spins governed by competing recombination processes is observed.
Numerical simulations and experiments are performed to investigate the use of thin conformal silicon nitride cladding layers to engineer the dispersion properties of silicon nanophotonic waveguides.
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