Undoped and Al-doped ZnO thin films have been prepared by the sol gel method. Zinc acetate dihydrate, ethanol and monoethanolamine were used as precursor, solvent and stabilizer, respectively. In the case of molarity study for Al-doped ZnO, aluminum nitrate nonahydrate was added to the precursor solution from 0 at. % to 6 at. % at molarity of 0.1 M, 0.2 M and 0.3 M. The optical properties were characterized using UV-Vis where the band gap of undoped ZnO increases as the annealing temperature increase and the band gap decrease as the molarity increment. Meanwhile the band gap increase upon increment of Al dopant under molarity of 0.1 M and 0.2 M due to Burstein-moss effects. Meanwhile at 0.3 M, the bandgap increase until 4 at. % of Al and suddenly decrease abruptly at 6 at. % of Al. The effect of molarity and dopant percentage on the thin film gives a different value of energy band gap.

The ray tracing of unclad U-shape multimode fiber optic is examined by using Zemax simulation have been proposed. The influence of the geometry of sensing region such as absorbing medium refractive index, n2, shape of fiber and the bending radius is analyzed. Number of analysis ray is determined and the value of n2 is varied at 1, 1.3314, 1.359, 1.36, 1.37 and 1.4. The intensity of light propagate inside the fiber is reducing at high n2 and this graph pattern is supported by experimental result. A U-shaped sensor is used for the analysis because of the sensitivity is higher than straight fiber design due to their higher penetration depth. Zemax simulation shows that the fiber with bending radius 1.5 mm has higher response compared to fiber with radius 2.5 mm. � 2017 Trans Tech Publications, Switzerland.

Criteria for development of high sensitivity surface plasmon resonance (SPR) sensor depends on several factors such as types of metals, light polarization modes, light coupling techniques and thicknesses of metal film. This paper discussed the effect of light excitation wavelength ranging from ultra violet (UV) region to infrared (IR) region on SPR. Three regions have been classified such as UV region (from ?=200nm to ?380nm), visible region (from ?=400nm to ?=633nm) and IR region (from ?=870nm to ?=1550nm). Noble metal gold thin film with thickness of 50nm and refractive index of n=0.1759+3.3104k was deposited on top of BK7 triangular prism (n=1.51). Very weak SPR signal was generated as the excitation wavelength was set in UV region. The signal's strength increased about 26.63% with the increment of wavelength from ?=200nm until ?=380nm, resulting the blue-shifting of SPR angle from 54.03�to 43.48�. The greatest excitation of SPP was significantly observed as the visible light region was incident through the thin film gold-coated prism represented by the abrupt decreased of Rmin to 96.50% at ?=633nm. The SPR angle was red-shifted about 0.30�throughout this region. The SPR signal getting weaker as light excitation wavelength entered the IR region (from ?=870nm to ?=1550nm) indicated by the 64.34% inclination of Rmin. In this region, the SPR angle was remain red-shifted from ?SPR=44.97�until ?SPR=46.18�with the average increment of 0.31�for each wavelength. It can be concluded that the usage of red laser, ?=633nm able to enhance the maximum excitation of SPP. The remarkable outcome of this work shows the vital role of light excitation wavelength in generating strong SPR signal for various application such as sensor and optoelectronic device. � 2018 Author(s).

Nowadays, surface plasmon resonance (SPR) sensor has been widely used in biosensing applications to detect the wide diversity of biomolecular interactions. There are few parameters need to be concerned in order to optimize the performance of SPR sensors such as film thicknesses, type of thin films and their configurations. In this study, we seek to determine the optimum thicknesses of hybrid thin films which consist of gold-graphene oxide layers for the enhancement of SPR sensor sensitivity. By using a theoretical approach, a WINSPALL 3.02 simulator had been used to investigate the effects of various thicknesses of hybrid configuration's thin films towards the excitation of surface plasmon polaritons (SPP). A layer of 3 nm protein was added to compare the maximum adsorption of the SPR sensor based on their configuration. It was found that the optimum thicknesses of gold and graphene oxide are 50 nm and 0.68 nm respectively for achieving best sensitivity. Thus, the sensitivity value for gold-GO thin films is higher than silver-GO which are 19.42 �/RIU and 5.45 �/RIU with FWHM = 2.28� and 0.64� respectively. � 2016 IEEE.

This study discussed the effect of nanocomposite film's thicknesses on the generation of SPR for detection of Pb2+ ions. Ag-GO nanocomposite film was deposited on the hypothenuse side of the triangular prism via Kretschmann configuration. The thicknesses of Ag-GO were varied between 50nm and 60nm by manipulating the Ag's thicknesses from 30nm to 50nm and GO's between 2nm and 10nm. The optimum SPR signal was obtained as thickness of Au-GO was fixed at 50nm with tAg=48nm and tGO=2nm resulting 75.77% of SPP excitation. As thicknesses of GO increased above 2nm and thicknesses of Ag were set less or more than 48nm, the SPP excitation became weaker. The sensitivity of SPR sensor shows a good agreement with the generation of SPP. The sensor exhibits the optimum sensitivity of s=0.452�/RIU with angle shifting of 0.905�as nanocomposite film under configuration of tAg=48nm: TGO=2nm and tAg=50nm: TGO=2nm were employed. In conclusion, the amplification of SPR sensor's sensitivity can be achieved by introducing 50nm nanocomposite films consist of �2nm thicknesses of GO. � 2018 IEEE.

Plastic optical fiber sensing that coated with ZnO is developed and its interaction with ethanol and methanol solution is investigated. ZnO is synthesized sonochemically by using the bath type sonicator. The optical properties such as transmittance, absorbance and refractive index of ZnO is determined by using ultraviolet-visible (UV-Vis) spectrophotometer. Then, the cladding of plastic optical fiber (POF) is etched by using acetone solution, sand paper and deionized water. The unclad region is coated with ZnO and being immersed in the solution of ethanol and methanol in the range from 0 v/v% to 50 v/v%. The performance of ZnO coated POF is achieved by obtaining the output power value that transmitted via power meter. The result of this research is as the alcohol concentration increase, the output power value increase. Refractive index of ZnO is varied due to interaction between modified-cladding area and alcohol. Besides that, more light propagates inside the fiber when the sensor is tested under methanol solution compare to ethanol. Thus, the output power ratio increments as well as the sensor efficiency and shows the effectiveness of POF sensor to detect varied alcohol concentration. � 2020 Trans Tech Publications Ltd, Switzerland.