N. Arsad

DESIGN AND CHARACTERIZATION OF MULTIPLE COUPLED MICRORING BASED WAVELENGTH DEMULTIPLEXER IN SILICON–ON–INSULATOR (SOI)

We report in this paper, an optimized design and characterization of SOI based single mode, four channels wavelength demultiplexer using microrings. The usage of silicon-on-insulator (SOI) allows a wide free spectral range (FSR) for the device that is crucial in developing ultra-compact integrations of planar lightwave circuits (PLCs). The characterizations are done using Finite-Difference Time-Domain (FDTD) mode simulations from RSOFT. Serially cascaded microring arrays up to the third order are presented to study the design trade-off among the FSR, Q-factor and optical losses of the laterally coupled wavelength demultiplexer. The demultiplexer is expected to be working at C-band region of Wavelength Division Multilplexing (WDM) for a wavelength around 1550 nm. Our proposed demultiplexer has low insertion loss (< 0.5 dB) and a crosstalk around 12 ~ 19 dB.

Polyethylene flow-injection for nitrite detection: Spectrotrophotometric method

A polyethylene flow-injection mechanism coupled with polymer optical fibre is developed to determine nitrite in aqueous solution based on direct absorbance spectrophotometric method. Sample of nitrite concentration ranging from 0.2156 μg/mL to 3.45 μg/mL is prepare for experiment. The result shows that peak wavelength of the absorbance is obtained at 545nm with a standard deviation range of 0.0004 to 0.0107 and precision of 0.5% to 0.03%. Meanwhile, limit of quantitation and limit of detection are found to be 0.158 μg/mL and 0.0052 μg/mL respectively. There results indicate satifactory parameters for analytical analysis with the sensor displays moderate overall sensitivity.

Development of POF flow-injection for spectrophotometric determination of nitrite

A POF flow injection cell is developed to determine nitrite in aqueous based on spectrophotometric method. The jacket of the POF is used as a chamber cell with 10mm core as pathlength. The direct absorbance spectrophometric principle is applied in this work and a range of 400nm to 650nm wavelengths were selected as the nitrite absorption region. Sample of nitrite concentration from 0.2156ppm to 6.9ppm are tested by using syringe pumped into the cell. Colorimetrie of the sample is produced by greiss reagent method. The method based on reaction of nitrite with sulphanilamide acid and N-l-napthylamine which caused pink colour azo dye proportional to the nitrite concentration present in the aqueous sample. The result shows that peak wavelength absorbance at 545nm with standard deviation range from 0.0004 to 0.0107 and precision from 0.5% to 0.03%. Meanwhile, limit of quantitation and limit of detection are 0.158ppm and 0.0052ppm, respectively. These results indicate satisfied parameters for analytical analysis and sensitivity was moderate.

Ultraviolet sensing by al-doped ZnO thin films

We report the fabrication and characterization of an ultraviolet photoconductive sensing by using Al-doped ZnO films. Undoped ZnO, 1 at.% and 2 at% of Al were prepared on quartz glass by sol gel method with annealing temperature of 500°C for 1 hour. The presence of spherical shaped nanoparticles were detected for undoped ZnO by using FESEM. The absorption edge shifted to a lower wavelength by doping with Al and excitonic peak can be observed. The band gap values increased by adding Al. I-V curves reveal an ohmic line and improvement in electrical conductivity when the samples are illuminated by ultraviolet (UV) light with a wavelength of 365 nm. At 1 at.% of Al, the film have a larger increment in photocurrent response when illuminated with UV light compared to undoped ZnO and 2 at.% Al. The thin films have a longer recovery time than response time.