Optimized design on high-power GaN-based Micro-LEDs - art. no. 684108

The structure of micro-LEDs was optimized designed. Optical, electrical and thermal characteristics of micro-LEDs were improved. The optimized design make micro-LEDs suitable for high-power device. The light extraction efficiency of micro-LEDs was analyzed by the means of ray tracing. The results shows that increasing the inclination angle of sidewall and height of mesa, and reducing the absorption of p and n electrode can enhance the light extraction efficiency of micro-LEDs. Furthermore, the total light output power can be boosted by increasing the density of micro-structures on the device. The high-power flip-chip micro-LEDs were fabricated, which has higher quantum efficiency than conventional BALED's. When the number of microstructure in micro-LEDs was increased by 57%, the light output power was enhanced 24%. Light output power is 82.88mW at the current of 350mA and saturation current is up to 800mA, all of these are better than BALED which was fabricated in the same epitaxial wafer. The IN characteristics of micro-LEDs are almost identical to BALED.

Color filter-less technology of LED back light for LCD-TV - art. no. 68410G

Back Light Unit (BLU) and Color Filter are the two key components for the perfect color display of Liquid Crystal Display (LCD) device. LCD can not light actively itself, so a form of illumination, Back Light Unit is needed for its display. The color filter which consists of RGB primary colors, is used to generate three basic colors for LCD display. Traditional CCFL back light source has several disadvantages, while LED back light technology makes LCD obtain quite higher display quality than the CCFL back light. LCD device based on LED back light owns promoted efficiency of display. Moreover it can generate color gamut above 100% of the NTSC specification. Especially, we put forward an idea of Color Filter-Less technology that we design a film which is patterned of red and green emitting phosphors, then make it be excited by a blue light LED panel we fabricate, for its special emitting mechanism, this film can emit RGB basic color, therefore replace the color filter of LCD device. This frame typically benefits for lighting uniformity and provide pretty high light utilization ratio. Also simplifies back light structure thus cut down the expenses.

Butt-Joint Monolithicaily Integrated DFB-LD/EA-MD Light Source for 10Gbit/s Transmission

This paper reports on the design, fabrication, and performance of an integrated electro-absorptive modulated laser based on butt-joint configuration for 10Gbit/s application. This paper mainly aims at two aspects. One is to improve the optical coupling between the laser and modulator; another is to increase the bandwidth of such devices by reducing the capacitance parameter of the modulator. The integrated devices exhibit high static and dynamic characteristics. Typical threshold current is 15mA,with some value as low as 8mA. Output power at 100mA is more than 10mW. The extinction characteristics,modulation bandwidth, and electrical return loss are measured. 3dB bandwidth more than 10GHz is monitored.

Design of spectrometer based on volume phase grating for near infrared range

In order to design and fabricate a spectrometer for the infrared range widely used in the different applications, Volume Phase Grating (VPG) with. low Polarization Dependence Loss (PDL) and high efficiency has been adopted as the dispersion element. VPG is constructed by coating an optical substrate with a thin film of dichromated. gelatin and exposing the film to two mutually coherent laser beams to form index modulation. The diffraction efficiency for a VPG is governed by Bragg effects. The depth (d) and index modulation contrast of the grating structure control the efficiency at which the light is diffracted when the Bragg condition is satisfied. Gradient index lens with high performance and low aberration are used as collimating system instead of standard lens. The spot diagrams and MTF curve of the collimating lens are shown in the paper. The receive system is InCaAs photodiode (PD) array including 512 pixels with 25 mum pitch. The spectrum resolution of the spectrometer reaches to 0.2nm and wavelength accuracy is 40pm.

Design of side-pumped Nd : YAG lasers

Design of the typical laser diode side-pumped Nd:YAG rod system has been discussed using the conventional ray tracing method in this paper. Firstly introduce two basic matrices, refractional and translational matrix, described the transmission of nonparaxial light ray in the medium without concerning the absorption of light. And then, using those matrices, analyze the distribution of pump light in the crystal respectively under the condition of directly pumped system and indirectly pumped system with a cylindrical quartz rod as focusing lens. From the result of simulation, we compare the advantage and disadvantage of the two pumped method, and mainly consider how to select the diameter of the focus lens and cooling tube, indicate the effect of deionized water and cooling tube have on the pump light distribution in the active material. At last, make some conclusions about the side-pumped Nd:YAG laser system.

Design and fabrication of GaAs OMIST photodetector

We designed and fabricated GaAs OMIST (Optical-controlled Metal-Insulator-Semiconductor Thyristor) device. Using oxidation of A1As layer that is grown by MBE form the Ultra-Thin semi-Insulating layer (UTI) of the GAAS OMIST. The accurate control and formation of high quality semi-insulating layer (AlxOy) are the key processes for fabricating GaAs OMIST. The device exhibits a current-controlled negative resistance region in its I-V characteristics. When illuminated, the major effect of optical excitation is the reduction of the switching voltage. If the GaAs OMIST device is biased at a voltage below its dark switching voltage V-s, sufficient incident light can switch OMIST from high impedance low current"off"state to low impedance high current "on"state. The absorbing material of OMIST is GaAs, so if the wavelength of incident light within 600 similar to 850nm can be detected effectively. It is suitable to be used as photodetector for digital optical data process. The other attractive features of GaAs OMIST device include suitable conducted current, switching voltage and power levels for OEIC, high switch speed and high sensitivity to light or current injection.

Design of high brightness cubic-GaN LEDs grown on GaAs substrate

The Principle of optical thin film was used to calculate the feasibility of improving the light extraction efficiency of GaN/GaAs optical devices by wafer-bonding technique. The calculated results show that the light extraction efficiency of bonded samples can be improved by 2.66 times than the as-grown GaN/GaAs samples when a thin Ni layer was used as adhesive layer and Ag layer as reflective layer. Full reflectance spectrum comparison shows that reflectivity for the incident light of 459.2 nm of the bonded samples was improved by 2.4 times than the as-grown samples, which is consistent with the calculated results.

Design of Photonic Crystal Semiconductor Optical Amplifier With Polarization Independence

Slow-light effects in photonic crystal (PC) waveguides can enhance light-mater interaction near the photonic band edge, which can be used to design a short cavity length semiconductor optical amplifier (SOA). In this paper, a novel SOA based on slow-light effects in PC waveguides (PCSOA) is presented. To realize the amplification of the optical signal with polarization independence, a PCSOA is designed with a compensated structure. The cascaded structure leads to a balanced amplification to the TE and TM polarized light.

Generation of optimized wavelength-tunable optical pulse from an uncooled gain-switched Fabry-Perot semiconductor laser using optical amplifier as external light injection

We present a novel system design that can generate the optimized wavelength-tunable optical pulse streams from an uncooled gain-switched Fabry-Perot semiconductor laser using an optical amplifier as external light source. The timing jitter of gain-switched laser has been reduced from about 3 ps to 600 fs and the pulse width has been optimized by using our system. The stability of the system was also experimentally investigated. Our results show that an uncooled gain-switched FP laser system can feasibly produce the stable optical pulse trains with pulse width of 18 ps at the repetition frequency of 5 GHz during 7 h continuous working. We respectively proved the system feasibility under 1 GHz, 2.5 GHz and 5 GHz operation. (c) 2008 Elsevier B.V. All rights reserved.

Charge stripping accumulation of light heavy ions in HIRFL-CSR main ring

The charge stripping injection method has been adopted for the accumulation of light heavy ions in HIRFL-CSR. This method has some special requirements for the accelerating particles, and at the same time the structure of the injection orbit has to be changed. In this paper, the design of the orbit has been presented, as well as the calculation of the beam line matching. According to the result of commissioning, stripping injection can accumulate the beam to a higher current.

Study of the LED based light calibration system for neutron wall detector

The light calibration system is one of the key components of Neutron Wall detector. It is used to calibrate the electronics and to monitor the long-term stability of the detector modules. With the detaile investigations, a calibration system with high-power LED (3W) driven by the fast pulses has been carried out. It is also tested together with the detector module of the Neutron Wall and the result of the preliminary calibration demonstrates that it fulfills the needs. It's a new design proposal to the light calibration system of the fast scintillator detector.

Design studies on the 4 pi gamma-ray calorimeter for the ETF experiment at HIRFL-CSR

A high detection efficiency calorimeter which is used to detect gamma-rays with energies from 1 MeV up to 10 MeV as well as light charged particles has been proposed. Design of the geometry, results of the crystal tests and Monte Carlo simulations are presented in this paper. The simulation results confirm that the calorimeter can obtain high detection efficiency and good energy resolution with the current designed geometry. And the calorimeter is competent for the future External Target Facility (ETIF) experiments.

Highly efficient inverted top-emitting organic light-emitting diodes using a lead monoxide electron injection layer

By introducing an effective electron injection layer (EIL) material, i.e., lead monoxide (PbO), combined with the optical design in device structure, a high efficiency inverted top-emitting organic light-emitting diode (ITOLED) with saturated and quite stable colors for different viewing angles is demonstrated. The green ITOLED based on 10-(2-benzothiazolyl)-1, 1, 7, 7-tetramethyl-2, 3, 6, 7-tetrahydro-1H, 5H, 11H-[1] benzopyrano [6, 7, 8-ij] quinolizin-11-one exhibits a maximum current efficiency of 33.8 cd/A and a maximum power efficiency of 16.6 lm/W, accompanied by a nearly Lambertian distribution as well as hardly detectable color variation in the 140 forward viewing cone. A detailed analysis on the role mechanism of PbO in electron injection demonstrates that the insertion of the PbO EIL significantly reduces operational voltage, thus greatly improving the device efficiency.

A Novel Biodegradable and Light-Breakable Diblock Copolymer Micelle for Drug Delivery

A facile approach to the preparation of light-responsive copolymer micelles is developed. This approach is based on the attachment of hydrophobic groups to one block of a diblock copolymer via a light-sensitive linkage. The micelles can be dissociated under light irradiation and release the encapsulated pyrene. The obtained polymeric micelles are expected to be of use as drug-delivery vehicles.

Design of polymeric stabilizers for size-controlled synthesis of monodisperse gold nanoparticles in water

A new methodology is described for the one-step aqueous preparation of highly monodisperse gold nanoparticles with diameters below 5 nm using thioether- and thiol-functionalized polymer ligands. The particle size and size distribution was controlled by subtle variation of the polymer structure. It was shown that poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) were the most effective stabilizing polymers in the group studied and that relatively low molar mass ligands (similar to 2500 g/mol) gave rise to the narrowest particle size distributions. Particle uniformity and colloidal stability to changes in ionic strength and pH were strongly affected by the hydrophobicity of the ligand end group. "Multidentate" thiol-terminated ligands were produced by employing dithiols and tetrathiols as chain-transfer agents, and these ligands gave rise to particles with unprecedented control over particle size and enhanced colloidal stability. It was found throughout that dynamic light scattering (DLS) is a very useful corroboratory technique for characterization of these gold nanoparticles in addition to optical spectroscopy and TEM.