With the development of GNSS systems, it has become a tendency that radio occultation is used to sense the Earth’s
atmosphere. By this means, the moisture, temperature, pressure, and total electron content can be derived. Based on the
sensing results, more complicated models for atmosphere might come into being. Meteorology well benefits from this
technology. As scheduled, the BD satellite navigation system will have a worldwide coverage by the end of 2020. Radio
occultation studies in China have been highlighted in the recent decade. More and more feasibilities reports have been
published in either domestic or international journals. Herein, some scenarios are proposed to assess the coverage of
radio occultation based on two different phases of BD satellite navigation system. Phase one for BD is composed of
GEO,IGSO and several MEO satellites. Phase two for BD consists mostly of 24 MEO satellites, some GEO and IGSO
satellites. The characteristics of radio occultation based on these two phases are presented respectively.
For enhancing the output efficiency of GaN light-emitting diode(LED), we calculated the band structure of photonic
crystal(PhC), and designed and fabricated several novel GaN LEDs with photonic crystal on Indium-Tin-Oxide(ITO),
which as p-type transparent contact of GaN LED. In this fabricating process, we developed conventional techniques in
order that these methods can be easily applied to industrial volume-production. And we have done some preliminary
experiments and obtained some results.
Nowadays, high power LED is often packaged with flip chip method. The gold bump is usually made by electroplating
or gold evaporation, which cause the environment pollution and material waste. A gold wire bump manufacture
technology for high power LED flip chip is described in this paper. The wire bond device is used and different bump
making parameters, such as weld temperature, pressure and ultrasonic power, are optimized through experiments. At the
same time, a new bump wire tail height managing process is introduced. The gold wire bump with this method height
difference keep in 3 micrometers and which is convenient for flip chip. Then, rapid annealing is taken to make sure the
gold wire bump has a well adherence to the wafer. At last, the bump weld result is tested and the bump invalidation is
analyzed with the SEM. The bonding force between bump and wafer more than 10 grams. The flip chip high power LED
with gold wire bump has low forth voltage and heat resistance. All of above proved that the gold wire bump is
convenient and reliable for high power flip chip LED.
For reducing turn-on voltage of GaAs-based HBT, Al0.25Ga0.75As/GaAs0.89Sb0.11/GaAs DHBTs on GaAs (001) is successfully grown by solid-source molecular beam epitaxy (SSMBE) with a GaAs decomposition source, no misfit dislocation in the base layer was found by observation of SEM. It suggests that GaAsSb base layer is fully strained. Device with 75x75μm2 emitter mesa area is fabricated using this structure and yielded an excellent performance with high current gain of 30 at the collector current density of 2×103A/cm2 and low turn-on voltage of 0.8V. Due to the smaller band gap of the GaAsSb base layer, GaAsSb is useful material for reducing turn-on voltage of GaAs-based HBTs.
Lattice-matched InGaP on GaAs substrate was successfully grown by solid-source molecular beam epitaxy (SSMBE) with a GaP decomposition source. 0.5um-thick InGaP epilayer shows photoluminescence (PL) peak energy as large as 1.962eV, PL FWHM as small as 9.4meV, X-ray diffraction (XRD) rocking curve line-width as narrow as 25arcsec. The electron mobility of undoped, Si-doped InGaP layers measured by Hall are comparable to similar InGaP/GaAs heterojunction grown by SSMBE with other source or other growth techniques. Then the InGaP/GaAs HBT epiwafer is grown by this way. Beryllium(Be) diffusion is reduced by increasing the As/Ga flux ratio. Heterojuction Bipolar Transistor (HBT) with 75×75um2 emitter mesa area fabricated using this structure yielded an excellent performance with high current gain. The results reveal that InGaP/GaAs heterojunction grown by the present growth way have great potential application for semiconductor devices.
The laser-induced damage thresholds, weak absorption and damage morphology of ZnS/MgF2 interference filters, which were designed to pass radiation around a wavelength of 1064 nm, have been examined. The theory about the electric field and the temperature rise in the multilayer was presented to explain the phenomena, which were observed in the experiments.
We developed several ten sorts of harmonic mirrors, anti- reflector and separator coatings for cavity components, lens, separators to satisfy the needs of YAG harmonic laser system. This paper mainly introduced the optical properties and the damage thresholds of some of these coatings. At a normal or a 45 degree incidence angle, the separators satisfied the requirements such as HR for 1 (omega) , 2 (omega) /HT for 3 (omega) , or HR for 2(omega) /HT for 1 (omega) , 2(omega) , or HR for 2 (omega) , 4(omega) , and the mirrors or anti-reflectors could be simultaneously used for two or three wavelengths among the base wavelength 1053nm and its second, third, fourth harmonic wavelength.
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