Wee-Ong Siew

Red-green-blue laser emissions from dye-doped poly(vinyl alcohol) films.

A microscope slide acting as a passive waveguide was coated by three separate poly(vinyl alcohol) films that were doped with Coumarin 460, Disodium Fluorescein, and Rhodamine 640 perchlorate. On collinear pumping by a nitrogen laser, these dyes furnished primary red-green-blue laser emissions that were collected and waveguided by the microscope slide but exited from both ends. Frosting the waveguide exit introduced light scattering at the glass-air interface and spatially overlaid the red-green-blue laser emissions that emerged as a uniform white-light beam.

Hybrid model for dynamic power management

Dynamic Power Management (DPM) is a system level power management technique that selectively shut down idle electrical components to save power. Previous works are mainly focused on certain types of prediction technique which assume that the idle period is long range dependent (heuristic prediction based on past history), random process (Markov Process) or short range dependent (Autoregressive) characteristic. However, the user behavior is highly variable and single assumption might not hold for all conditions. Thus, techniques based on the above assumptions will only be effective in certain condition only. Hence, we propose here a Hybrid Model DPM system that combines Moving Average (MA), Time Delay Neural Network (TDNN) and random walk model to perform idle period prediction. The Hybrid Model will first analyze the Long Range Dependency and central tendency of the past idle period time series, and choose the most appropriate strategy for future idle period prediction. Simulation results show that the Hybrid Model achieves higher power saving in most of the scenarios compared to the other methods.

Space and time-resolved optical emission spectroscopy in TEA-CO/sub 2/ laser ablation of polymers and graphite

The luminous plumes from the TEA-CO/sub 2/ laser ablation of polymethylmethacrylate, polyimide, polyethylene terepthalate, and graphite in helium were characterized by using gated optical emission spectroscopy that measured the spatial-temporal distribution of singly ionized carbon species, and also by streak photography that examined the dynamics of the propagation of the luminous plumes. The plume splitting was implicated by the fast and slow components of plume species in curve-fitting their spatial-temporal distribution with the shifted Maxwell-Boltzmann distribution function. The best-fit velocities of the fast components were confirmed by the streak photographs.

Dynamics of double plume emissions in TEA-CO/sub 2/ laser ablation of graphite

Streak photography of TEA-CO/sub 2/ laser ablation of graphite in helium (He) and argon (Ar) background gases shows two luminous fronts, that are spatially and temporally separated, lifting off the graphite target. The velocity profile of the second front appears to follow closely that of the first luminous front. The second front is absent if the laser-supported absorption wave sets in when the background gas pressure is increased to 50-mbar Ar. The optical emission spectroscopy display many of triply, doubly, and singly ionized carbon species in the expanding plume at <0.3 mbar He, while the excited and singly ionized helium species are found in (1-30) mbar He which coincides with streak observations of strong luminous fronts. Computer simulations of the propagation trajectories of luminous fronts are carried out using the blast-wave, drag, and the snowplow models.

Parametric Studies of Pulsed Laser Deposition of Indium Tin Oxide and Ultra-thin Diamond-like Carbon for Organic Light-emitting Devices

Device quality indium tin oxide (ITO) films are deposited on glass substrates and ultra-thin diamond-like carbon films are deposited as a buffer layer on ITO by a pulsed Nd:YAG laser at 355 nm and 532 nm wavelength. ITO films deposited at room temperature are largely amorphous although their optical transmittances in the visible range are > 90%. The resistivity of their amorphous ITO films is too high to enable an efficient organic light-emitting device (OLED), in contrast to that deposited by a KrF laser. Substrate heating at

Triggered Spark Gap Command Charger for High Repetition Rate Applications

200^{\circ}C

A Two-Stage Spark Gap for Blumlein-Driven Transversely Excited Atmospheric Nitrogen Laser

with laser wavelength of 355 nm, the ITO film resistivity decreases by almost an order of magnitude to

Effects of Peaking Capacitor in a Copper Bromide Vapor Laser

2{\times}10^{-4}\;{\Omega}\;cm

Discharge Stability and Performance of a Small-Bore, Fast-Axial-Fow CO2 Laser Using New Pin Anodes

while its optical transmittance is maintained at > 90%. The thermally induced crystallization of ITO has a preferred directional orientation texture which largely accounts for the lowering of film resistivity. The background gas and deposition distance, that between the ITO target and the glass substrate, influence the thin-film microstructures. The optical and electrical properties are compared to published results using other nanosecond lasers and other fluence, as well as the use of ultra fast lasers. Molecularly doped, single-layer OLEDs of ITO/(PVK+TPD+

Temporal characteristics of short pulse dye mixture lasers

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