The success in fabrication of Cr-doped fibers (CDFs) with fluorescence of Cr3+ by powder-in-tube (PIT) method equipped with drawing-tower process is demonstrated for the first time. The fluorescence intensity of CDFs by fabricated RIT method is weak because the concentration of Cr-ion in Cr:YAG rod is low. However, the fabrication with powder-in-tube (PIT) provides a better solution to improve the concentration of Cr-ion to enhance the fluorescence of CDFs. The Cr-doped powder was composed of CaO-Al2O3-BaCO3-MgO-Cr2O3 as the material of core and then it was poured into the silica tube with outer diameter of 20 mm and inner diameter of 7 mm (20/7) to yield the perform. The CDFs had a 17.5 £gm core and a 125 £gm cladding. The transmission loss was 0.74 dB/cm at 1550 nm. And the fluorescence intensity of Cr3+ between 800~1200 nm was 50 nW/nm. To reduce transmission loss further, we used multi-tubes to raise the ratio of cladding to core. According to the principle of conservation of mass, the core diameter of CDFs was 5 £gm. The transmission loss was improved more than 50% and it reached to 0.135 dB/cm at 1550 nm. Moreover, a single-mode characteristic of CDF was observed when the propagation wavelengths were longer than 1260 nm. The CDFs were successfully fabricated by using a fiber drawing-tower technique with PIT method. The demonstration of CDFs makes it possible as a new generation broadband fiber amplifier, a tunable NIR fiber laser for sensor applications, and a broadband source for high resolution OCT.

No description available.

The optical properties of Mg-doped InN thin films grown on YSZ substrates have been investigated by photoluminescence (PL). A series of InN:Mg samples with various Mg cell temperatures (TMg) were produced by molecular beam epitaxy. The effect of Mg concentration on PL emission properties have been explored by various excitation power and temperature dependent measurements. The PL spectra as a function of excitation power exhibited a pronounce blueshift, indicating prominent band filling caused by the Burstein-Moss effect. Meanwhile, a typical redshift was observed as temperature increased due to bandgap shrinkage. The samples with TMg below 210 ˚C have a dominant peak at energy of 0.68 eV. In contrast, the PL peak emissions for films with a high TMg between 210~230 ˚C were centred near 0.6 eV. No PL emission was observed from the films with TMg above 230 ˚C. By fitting with an empirical Arrhenius equation, the activation energies yield approximately 20 meV and 15 meV for the lower and higher energy transitions, respectively. The fundamental optical properties of Zn doped InN were also examined. InN:Zn films were grown under In-rich conditions. The samples showed well defined PL emission spectra implying that the quality of the film has been improved over the Mg-doped series. The PL spectra of InN:Zn exhibited prominent features containing various emission peaks. The combination of excitation power and temperature dependent measurements supports a precise determination for the origins of the observed transitions. The comparison between the optical properties of Mg and Zn doped InN provide the motivation for more precise quantitative interpretation of p-type InN.

No description available.

by Pei-hsuon Chan. / Parallel title in Chinese characters. / Thesis (M.Ph.)--Chinese University of Hong Kong, 1988. / Bibliography: leaves 227-231.

As Si MOS approaches its maximum limits in speed and bandwidth, new devices are desired to meet the needs of high speed communications and signal processing. A device that exhibits superior performance to Si MOS, BJT, and GaAs technology is the HEMT (high electron mobility transistor). The HEMT offers superior transconductance, mobility, speed, and noise performance compared to Si MOS, BJT, and standard GaAs technology. The high performance is a result of improved channel mobility due to a heterojunction. At the heterointerface, the majority carriers are confined to a very thin sheet forming what has been termed a 2DEG (two dimensional electron gas). The purpose of this thesis is to demonstrate the suitability of Honeywell's delta-doped self-aligned complimentary HIGFET process for the realization of high speed analog circuits. An operational amplifier and switched-capacitor circuit are presented. The operational amplifier has been fabricated at Honeywell and preliminary tests have been performed on the op-amp which are also presented. / Graduation date: 1998

Graduation date: 1994

Split and normal gate A1GaAs /GaAs MODFETs were fabricated along with the ohmic test structures and the Hall bar geometries. The DC characteristics of normal gate transistors were evaluated at room temperature and at 77K and the threshold voltages were extracted from the measurements and compared to the theoretical results. The performance of normal gate transistors was reasonable. The sheet carrier density and the mobility extracted from Hall measurements using the Hall bar geometry showed increase of carrier density with increasing gate voltage and an increase of mobility with increasing carrier density. The contact resistance obtained from the ohmic test structure was high and not uniform within the sample. / Graduation date: 1991

With today's technology, a variety of styles and a variety of different LED material was produced. The development of LED in the same time, the vendor industry in order to defend their own interests and under the huge business opportunities, and each side of the application of the style-related intellectual property rights in the LED,although the wise limits of property rights, but also contributed to a more diverse The LED manufacturing methods have been developed. Our experiment is the YAG:Ce3+ doped other compounds (for example: copper,aluminum, ...) in a small test tube and in within the near vacuum of a state to do the open end of the seal, and then make a small test tube temperature heating, hopes the doping elements in the impact of high temperatures contributed to YAG:Ce3+ to adjust the lasing wavelength, and in vitro experiments also found with the increase of heating temperature photoluminescence intensity for a gradual downward trend. The YAG:Ce3+ yellow phosphor surface facing the shortcomings of a defect, so we research for YAG:Ce3+ phosphors adsorbed on the surface of anti-reflective film to be improved and modified YAG:Ce3+ has a surface defect observation showed that after modification surface defects of the YAG:Ce3+ emission intensity on increase in the phenomenon. We will also anti-reflective film adsorbed on the YAG:Ce3+ compounds used in fluorescent plastic surface on top, and with the original YAG:Ce3+ phosphors are made of rubber making to compare, comparison of the fluorescent plastic found on YAG:Ce3+ surface adsorption anti-reflective film for luminescence efficiency and the absorption rate for the blue light has a better performance.

The success in fabrication of Cr-doped fibers (CDFs) with fluorescence of Cr3+ by powder-in-tube (PIT) method equipped with drawing-tower process is demonstrated. However, the fabrication by using powder-in-tube (PIT) with redrawing technique provides a better solution to improve the concentration of Cr-ion to enhance the fluorescence of CDFs. The Cr-doped powder was composed of CaO-Al2O3-BaCO3-MgO-Cr2O3 as the material of core. The CDFs had a 7 £gm core and a 125 £gm cladding. The transmission loss was 0.27 dB/cm at 1550 nm and a core non-circularity of less than 3% for the CDFs are achieved. The fluorescence intensity of Cr3+ between 800~1200 nm was 6 nW/nm. The optical fiber fabrication processes, whether the preform is made by MCVD(Modified Chemical Vapor Deposition), RIT(Rod-in-Tube) or PIT, the inter-diffusion between core and cladding materials is an inevitable issue at such high fiber drawing temperature. Since SiO2 is amajor component in the cladding, SiO2 will certainly diffuse into the core region and become one of the new constituents in the core. The Cr-doped powder was composed of SiO2- Al2O3-MgO-K2O-TiO2-Cr2O3 as the material of core. The CDFs had a 10 £gm core and a 125 £gm cladding. The fluorescence intensity of Cr4+ between 900~1300 nm was 200 pW/nm. The CDFs were successfully fabricated by using podwer-in-tube with redrawing technique. The demonstration of CDFs makes it possible as a new generation broadband fiber amplifier and a broadband source for high resolution OCT.