UV Photoluminescence of Alumino-Germano-Silicate Glass Optical Fiber Incorporated with Gd2O3 Nano-Particles Upon Illumination of Xenon-Lamp.

Alumino-germano-silicate glass optical fiber incorporated with Gd2O3 nano-particles (NPs) was developed by using the modified chemical vapor deposition and the drawing process. The formation of spherical Gd2O3 NPs in the fiber core with average diameter of 10.8 nm was confirmed by the TEM. The distinct absorption peaks in the fiber preform appearing in the UV region at 205, 247, 253, 274, and 312 nm were due to the incorporated Gd2O3 NPs via reorganization of the seven 4f electrons into various multiplets of Gd ions. In the case of the optical fiber obtained by drawing of the preform at high temperature about 2150 °C, absorption peaks due to Gd2O3 NPs were found to appear at 383 and 455 nm, which were red-shifted from 274 and 312 nm of the preform, respectively, and it may be due to increase in the size of Gd2O3 NPs after the drawing process. To investigate the photoluminescence (PL) property for UV sensor applications, the PL of the fiber was obtained by illumination of the Xenon-lamp. A PL band appeared in the wavelength band from 370 nm to 450 nm, centering at about 400 nm, which can be attributed to the presence of Gd2O3 NPs embedded in the fiber core. It was also found that the PL intensity at 400 nm showed linear dependence with the excitation power from 0 to 400 W.

Temperature and Vibration Dependence of the Faraday Effect of Gd2O3 NPs-Doped Alumino-Silicate Glass Optical Fiber.

All-optical fiber magnetic field sensor based on the Gd2O3 nano-particles (NPs)-doped alumino-silicate glass optical fiber was developed, and its temperature and vibration dependence on the Faraday Effect were investigated. Uniformly embedded Gd2O3 NPs were identified to form in the core of the fiber, and the measured absorption peaks of the fiber appearing at 377 nm, 443 nm, and 551 nm were attributed to the Gd2O3 NPs incorporated in the fiber core. The Faraday rotation angle (FRA) of the linearly polarized light was measured at 650 nm with the induced magnetic field by the solenoid. The Faraday rotation angle was found to increase linearly with the magnetic field, and it was about 18.16° ± 0.048° at 0.142 Tesla (T) at temperatures of 25 °C-120 °C, by which the estimated Verdet constant was 3.19 rad/(T∙m) ± 0.01 rad/(T∙m). The variation of the FRA with time at 0.142 T and 120 °C was negligibly small (-9.78 × 10-4 °/min). The variation of the FRA under the mechanical vibration with the acceleration below 10 g and the frequency above 50 Hz was within 0.5°.

Effective supercontinuum generation by using highly nonlinear dispersion-shifted fiber incorporated with Si nanocrystals.

The dispersion-shifted fiber (DSF) incorporated with Si nanocrystals (Si-NCs) having highly nonlinear optical property was fabricated to investigate the effective supercontinuum generation characteristics by using the MCVD process and the drawing process. Optical nonlinearity was enhanced by incorporating Si nanocrystals in the core of the fiber and the refractive index profile of a dispersion-shifted fiber was employed to match its zero-dispersion wavelength to that of the commercially available pumping source for generating effective supercontinuum. The non-resonant nonlinear refractive index, n2, of the Si-NCs doped DSF measured by the cw-SPM method was measured to be 7.03 x 10(-20) [m2/W] and the coefficient of non-resonant nonlinearity, gamma, was 7.14 [W(-1) km(-1)]. To examine supercontinuum generation of the Si-NCs doped DSF, the femtosecond fiber laser with the pulse width of 150 fs (at 1560 nm) was launched into the fiber core. The output spectrum of the Si-NCs doped DSF was found to broaden from 1300 nm to wavelength well beyond 1700 nm, which can be attributed to the enhanced optical nonlinearity by Si-NCs embedded in the fiber core. The short wavelength of the supercontinuum spectrum in the Si-NCs doped DSF showed shift from 1352 nm to 1220 nm for the fiber length of 2.5 m and 200 m, respectively.

Investigation on the surface passivation of intrinsic a-Si:H thin films prepared by inductively coupled plasma-chemical vapor deposition for heterojunction solar cell applications.

Intrinsic a-Si:H thin films, which can have passivation functions on the surface of crystalline Si, were deposited by inductively coupled plasma chemical vapor deposition (ICP-CVD). The properties of the films were investigated at deposition temperatures ranging from 50 to 400 degrees C. The Si--H stretching mode at 2000 cm(-1), which indicates good film quality, was found in the range of 150-400 degrees C, but the film quality was not good at deposition temperatures below 150 degrees C. The passviation quality was determined by measuring the effective carrier lifetime using the quasi-steady state photoconductance (QSS-PC) technique. Two, 5, 7.5 and 10 nm thick films were deposited at 150 degrees C and annealed at 200 degrees C for 1 hour. The carrier lifetime of these films was approximately 3 times higher than that observed before annealing. A p a-SiC:H/i a-Si:H/n c-Si hetero-structure solar cell with a 7.8% efficiency and approximately 85% quantum efficiency (QE) was obtained by inserting an intrinsic a-Si:H thin film (5 nm) between the interfaces. These results highlight the potential applications of a passivation layer to heterojunction solar cells.

Preparation of phosphorus doped hydrogenated microcrystalline silicon thin films by inductively coupled plasma chemical vapor deposition and their characteristics for solar cell applications.

Intrinsic and phosphorus-doped hydrogenated microcrystalline silicon (microc-Si:H) films were prepared using inductively coupled plasma chemical vapor deposition (ICP-CVD) method. Structural, electrical and optical properties of these films were studied as a function of silane concentration, ICP source power and PH3/SiH4 gas ratio. Characterization of these films from Raman spectroscopy and X-ray diffraction revealed that the conductive film exists in microcrystalline phase embedded in an amorphous network. The condition of electrical properties (sigma(d): approximately 10(-7) S/cm, sigma(ph): approximately 10(-4) S/cm) and activation energy (0.55 eV), satisfied with properties of intrinsic microc-Si:H, was obtained at 1200 W of ICP power and 2% of silane concentration, respectively. At PH3/SiH4 gas ratio of 0.09%, dark conductivity has a maximum value of approximately 18.5 S/cm and optical bandgap also a maximum value of approximately 2.39 eV. The deposition rate was not satisfactory (4.9 angstroms/s) at same condition.

Luminescence enhancement by Au nanoparticles in Er(3+)-doped germano-silicate optical fiber.

We report on the fabrication of the Au nanoparticles/Er(3+) codoped germano-silicate fibers by modified chemical vapor deposition and solution doping processes. Absorption and luminescence characteristics of the Er(3+)-doped germano-silicate fibers incorporated with Au nanoparticles in the core of the fibers were investigated. The Au nanoparticles were found to be effective absorbents for hydroxyl groups to enhance the luminescence of Er(3+) ions upon pumping with the 980nm laser diode.

Characterization of intrinsic a-Si:H films prepared by inductively coupled plasma chemical vapor deposition for solar cell applications.

The hydrogenated amorphous silicon (a-Si:H) films, which can be used as the passivation or absorption layer of solar cells, were prepared by inductively coupled plasma chemical vapor deposition (ICP-CVD) and their characteristics were studied. Deposition process of a-Si:H films was performed by varying the parameters, gas ratio (H2/SiH4), radio frequency (RF) power and substrate temperature, while a working pressure was fixed at 70 m Torr. Their characteristics were studied by measuring thickness, optical bandgap (eV), photosensitivity, bond structure and surface roughness. When the RF power and substrate temperature were 300 watt and 200 degrees C, respectively, optical bandgap and photosensitivity, similar to the intrinsic a-Si:H film, were obtained. The Si-H stretching mode at 2000 cm(-1), which means a good quality of films, was found at all conditions. Although the RF power increased up to 400 watt, average of surface roughness got better, compared to a-Si:H films deposited by the conventional PECVD method. These results show the potential for developing the solar cells using ICP-CVD, which have the relatively less damage of plasma.

Effect of aluminum on the formation of silver metal quantum dots in sol-gel derived alumino-silicate glass film.

The effect of aluminum incorporation on silver metal quantum dots formation in the alumino-silicate glass film processed by sol-gel process was investigated. The sol-gel derived glass was coated onto the silica glass plate by spin coating with the mixture solution of tetraethyl orthosilicate (TEOS), C2H5OH, H2O, AgNO3, Al(NO3)3. 39H2O, and HNO3 with the molar ratios of Ag/Si = 0.12 and Al/Si varying from 0 to 0.12. The formation of the silver metal quantum dots was confirmed by the measurements of the UV/VIS optical spectra, the X-ray diffraction patterns, and the transmission electron microscope images. While the radius of silver metal quantum dots increased with the increase of aluminum concentration, the concentration of the silver metal quantum dots decreased. The formation of the silver metal quantum dots was found strongly suppressed by incorporation of aluminum ions in the glass. The change in the glass structure due to the aluminum incorporation was investigated by the analysis of the Raman spectra. The silver ions in the glass contributed to form stable (Al:Ag)O4 tetrahedra by pairing with aluminum ions and thus clustering of silver metal quantum dots was hindered.

Fabrication and optical characteristics of a novel optical fiber doped with the Au nanoparticles.

Optical fibers containing gold metal nanoparticles were developed by modified chemical vapor deposition, in which Au(OH)3 and tetraethyl-orthosilicate (TEOS) was used via sol-gel process to incorporate gold metals by providing the reduction atmosphere. The absorption peak appeared near 490 nm was found to be due to the surface plasmon resonance of the gold nanoparticles incorporated in the fiber core.

Development of Germano-Silicate Optical Fiber Incorporated with Germanium Nanoparticles and Its Optical Characteristics.

The germano-silicate optical fiber incorporated with Ge nanoparticles with enhanced optical nonlinearity was developed by using modified chemical vapor deposition and drawing processes. A broad photoluminescence band obtained by pumping with the 404 nm superluminescent diode was found to appear from 540 nm to 1,000 nm. The non-resonant nonlinear refractive index, n2, of the fiber measured by the continuous wave self-phase modulation method was 4.95 x 10(-20) m2/W due to the incorporated Ge nanoparticles in the fiber core. The enhancement of the non-resonant optical non-linearity may be due to the creation of the NBOs and other defects from the incorporated Ge-NPs in the fiber core.