Advanced Materials Research Vols. 55-57

Abstract: We firstly propose the simple system of an attosecond light pulse generation by using a soliton pulse circulating in the integrated micro ring devices. The ultra short pulse in the atto scale regime and its beyond can be easily generated. Simulation results obtained have shown that the generation of a very narrow pulse and sharp tip is achieved. In principle, light pulse known as soliton pulse is input into a three stage micro ring resonators, where the ring radii are within the range from 5-15 microns. With some selected parameters such as ring radius, coupling ratio and nonlinear refractive index, the attosecond pulse is generated and achieved. The potential applications of using such a narrow pulse for new generation optical lithography, high density CD writing, high resolution interferometer, surface roughness and high speed optical computing, quantum computing are discussed.

Abstract: In analysis of a new technique for quantum key distribution using the entangled photon within a micro ring resonator is presented. The Kerr nonlinear effects type of light circulates in the micro ring resonator is induced into the device. The superposition i.e. four-wave mixing of the propagating waves at resonance is occurred, where the entangled photon is generated. The possible two entangle pairs is described and discussed. The proposed system has shown the potential of using in the realistic system, where such a device scale can be fabricated and performed within the mobile telephone hand set, which means the use of quantum telephone will be realized in the near future.

Abstract: II-VI inorganic/organic heterostructures consisting of ZnSe and tris(8-hydroxyquinoline) aluminum (Alq3) were prepared by electron beam evaporator. Alq3 layer with 20 nm was grown between 200-nm ZnSe layers. Photoluminescence measurement was conducted at various temperatures in order to investigate the important temperature-dependent parameters of this structure. PL spectra revealed thermal population of exciton state and the change in PL quantum efficiency of the film.

Abstract: In this work, titanium dioxide (TiO2) nanocrystals were prepared via spray pyrolysis process under high electric field, and were used for tuning the light scattering properties of poly(methyl methacrylate) (PMMA) sheets by embedding their nanopowders in PMMA matrix. The effect of processing conditions such as precursor concentration and calcination temperature on morphology and particle size was investigated. The sprayed and calcined TiO2 nanopowders were characterized by XRD, SEM and TEM. The intensity of the light radiation for TiO2/PMMA hybrid sheets was measured using a LUX meter. It was suggested that the efficiency of TiO2 nanocrystals can be increased dramatically by controlling both the particle size and the morphology. For TiO2/PMMA nanocomposite hybrid sheets, the light scattering capability was found to be about 15 times higher than that of pristine PMMA sheets at the distance of 30 cm.

Abstract: Titanium dioxide/poly(methyl methacrylate) (TiO2/PMMA) hybrid films with various amounts of TiO2 containing PMMA resin on PMMA sheets were produced by a tape casting method. TiO2 nanocrystals were prepared using electrospraying process at 400oC under high electric field of 3 kV/cm. The as-sprayed and annealed TiO2 powders were characterized by Raman spectroscopy, XRD, SEM and TEM. The UV absorption for both pristine PMMA sheet and TiO2/PMMA hybrid film on PMMA sheet was measured using UV-Vis spectroscopy. The as-sprayed and annealed TiO2 powders showed anatase preferred orientation. They have higher UV absorption in the range of wavelength between 230 and 370 nm than commercial anatase TiO2 nanopowders. Moreover, the visible light transmittances of anatase TiO2/PMMA hybrid films on PMMA sheets in the range of wavelength between 400 and 800 nm was comparable with those derived from pristine PMMA sheets. Therefore, the resulting hybrid films can block out the UV rays, but are transparent to visible light.

Abstract: his paper proposes the interesting nonlinear behavior of light known as bifurcation, where the use of such behavior in a micro ring resonator to form the secure digital codes for optical packet switching application is demonstrated. A new concept of the stop-start bits in an optical packet switching protocol is formed by using the bifurcation codes. The bifurcation is introduced when light is input into a nonlinear micro ring device, where the refractive index of an InGaAsP/InP is one of device parameters. The other parameters of the device are coupling coefficient (K) and the ring radius (R), where the ring radii used are ranged from 5-10 microns. Simulation results obtained have shown that the packet switching data can be secured by using the generated start-stop bits as the secured codes.

Abstract: The fiber optic sensor system for chemical vapor detection was desiged and constructed. The system consisted of three parts; the optic unit, the fiber-optic sensing head and the flow controlling unit. The optic unit included a He-Ne laser source which lazes a red laser into an aligned optical fiber, a photo detector, and a signal processing with computer interface controlled by the Labview® program version 7.1. The sensing head was made of a polyaniline thin film coated onto the de-cladded section of an optical fiber covered by a gas mixing cell. The concentration of measured gas was controlled by varying nitrogen gas flow rate. The nitrogen flow controller was set-up to obtain vapor concentration in the range of 0.04 to 0.40 % v/v. Vapors of hydrochloric acid (HCl) and n-butyl amine (a weak base) were used to test the performance of the sensor system. It was found that output intensity increases with an increasing HCl concentration and decreases with increasing n-butyl amine concentration. The response toward the amine vapor was faster than that of the HCl vapor (23 seconds for n-butyl amine and 72 seconds for HCl). Experiments performed at various concentrations of amine vapor (between 0.04 to 0.21 %v/v) found that a higher concentration yields faster response time.

Abstract: Thin films of undoped, fluoride- and antimony- doped tin oxide on glass were prepared by spray pyrolysis technique. The aerosols were atomized from precursor solution by a commercial ultrasonic generator. Tin chloride(SnCl2.2H2O), ammonium fluoride (NH4F), and antimony chloride (SbCl3) were used as a source for tin, fluoride, and antimony respectively. For the undoped tin oxide film, the solution of 0.8 M tin chloride was used as a precursor solution. While fluoride-doped tin oxide films (FTO), the solution of 0.8 M SnCl2.2H2O in ethanol and varying amounts of NH4F dissolved in 0.2 M HCl (0.6 mL) were used as a precursor solution. The doping concentrations of NH4F were 0, 0.2, 0.3, 0.4, 0.5 and 0.6 M. For the antimony- doped tin oxide films (ATO), the doping concentrations of SbCl3 dissolved in butanol (10 mL) are 0, 0.016, 0.032, 0.048, 0.064 and 0.080 M. The aerosols were sprayed on the hot glass substrates by air at a flow rate of 1 L/minute through a PVC and glass tubing for 20 minutes for every solution. Substrate temperature was kept at 320 ± 15 °C for undoped and fluoride-doped tin oxide films and at 390 ± 20 °C for antimony- doped tin oxide films. The electrical and optical properties of the films were characterized by four-point probe measurement and UV/VIS spectrophotometer. The best FTO film exhibits the resistivity of 53.83 W-cm and the light transmission of 88.18%. While the best ATO exhibits the resistivity of 61.03 W-cm and the light transmission of 86.45%.

Abstract: This paper presents the relation between the staring cobalt thickness with carrier generation lifetime, which effects to the sensitivity of p-n junction temperature sensor. The starting cobalt thickness of 12, 20 and 30nm have been used. The carrier generation lifetimes have been calculated from the reverse current-voltage (I-V) characteristics. The highest carrier generation lifetime has been obtained in the case of 12nm starting cobalt thickness. The highest sensitivity of p-n junction temperature sensor has also been observed from the case of 12nm starting cobalt thickness. The sensitivity has been calculated from the relation between leakage current versus temperature. The sensitivity of p-n junction temperature sensor can be improved by increasing carrier generation lifetime.

Abstract: . We propose a new concept of a micro gyroscope which is made by a nonlinear micro ring resonator (i.e. 5-10 microns). The nonlinear behavior of polarized light known as polarization mode dispersion in the micro ring device is introduced by material birefringence (i.e. refractive index), which is described. In practice the measurement of polarization mode dispersion can be performed by projecting the output light into a polarizing beam splitter and detectors, where the change in phase is occurred, and then the birefringence is calculated. In addition, the property of the two orthogonal components (i.e. horizontal (H) and vertical (V) components) can be formed the photon entanglement. Which means the entangled photon can be generated, where the state timing walk-off can also be measured and compensated. The design of micro gyroscope is now capable to reduce the device scale in the micron regime to meet more possible applications such as for the measurement of temperature, pressure, and force based on birefringence sensor, which will be discussed in details.