We report on the dramatic ultrafast photo-enhancement of ferromagnetism on a 100 picosecond timescale in ion-implanted semiconductor GaMnAs via photoexcited transient carriers. This non-thermal, transient cooperative magnetic process surprisingly quenches at low temperatures, significantly bellow the Curie temperature.
We demonstrate a 2.3 mum emission at RT under quasi-CW operation from a Sb-based monolithic VCSEL. The structure is composed of 2 n-doped AlAsSb/GaSb DBR, a type-I GaInAsSb/AlGaAsSb QWs active region and a tunnel junction.
Coherent THz pulses at 328.2 mum were generated by mixing two CO2 laser frequencies based on collinear phase-matched difference-frequency generation in GaSe crystals. The highest average output power was measured to be 260 muW.
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.
Simultaneous near-field fluorescence lifetime imaging and atomic force microscopy identify radiative, interface and subsurface defect recombination sites in GaAs/GaInP heterostructures. Such unique characterization plays a significant role in identifying candidate samples for laser cooling.
By incorporating GaAs/AlGaAs based uni-traveling-carrier photodiodes with broadband micromachined monopole antennas, the demonstrated photonic-transmitter can radiate strong sub-THz pulses (20mW peak-power) with a wide bandwidth (100~250GHz), which was measured by another photonic-receiver for ultra-wideband communication.
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 integrated into GaN LEDs both two-dimensional photonic crystal patterns and angled sidewall deflectors. The resultant devices exhibited about three-fold enhancement in vertical emission intensity when compared with the planar reference LED device.
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.
We reported the systematical study of optical anisotropy of AlxGa1-xN epitaxial films grown on sapphire using FTIR measurements. The experimental data can be theoretically fitted by employing a four-phase layered model. Several specific absorption dips were observed when the aluminum composition is larger than 24%. The dip intensity increases with the aluminum compositions. According to the reciprocal...
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 present the concept and first results of a continuous wave room temperature operating electrically pumped GaSb-based VCSEL with buried tunnel junction as current aperture. Laser emission has been achieved at 2.3 mum.
High Q-factor (~60,000) whispering gallery modes are observed from GaAs based micropillar cavities with embedded InAs quantum dots. Low threshold lasing is observed in WGMs near to the peak of the QD ensemble.
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.
A high emitting efficiency GaN-based white LED with 2D PQC on surface and PSS were successfully fabricated. After packaging, 21% enhancement in emitting luminous flux was achieved under the driving current 20 mA.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.