ZnS:Mn nanocrystals thin film was fabricated at 300°C and 500°C via the spin coating method. Its sol-gel was spin coated for 20 s at 3000 rpm and 4000 rpm with metal tape being used to mold the shape of the thin film. A different combination of these parameters was used to investigate their influences on the fabrication of the film. Optical and structural characterizations have been performed. Optical characterization was analyzed using UV-visible spectroscopy and photoluminescence spectrophotometer while the structural and compositional analysis of films was measured via field emission scanning electron microscopy and energy dispersive X-ray. From UV-vis spectra, the wavelength of the ZnS:Mn was 250 nm and the band gap was within the range 4.43 eV–4.60 eV. In room temperature PL spectra, there were two emission peaks centered at 460 nm and 590 nm. Under higher annealing temperature and higher speed used in spin coating, an increase of 0.05 eV was observed. It was concluded that the spin coating process is able to synthesize high quality spherical ZnS:Mn nanocrystals. This conventional process can replace other high technology methods due to its synthesis cost.

Research comparing the advantages of spin coating and chemical bath deposition is going, and there are varied views on these methods. Here, we used spin coating and chemical bath deposition to prepare thin films of ZnS nanoparticles. The film was analysed by photoluminescence (PL) spectrophotometry, field emission scanning electron microscopy (FE-SEM), ultraviolet spectroscopy (UV-Vis), and energy-dispersive X-ray (EDX) spectroscopy. The UV-Vis spectra revealed that the wavelength of ZnS is between 220 nm - 320 nm while the PL spectra showed a peak centred in the blue region. Both spin coating and chemical bath deposition rendered spherical nanoparticles but of different sizes 17.9 nm and 21.2 -25.7 nm, respectively. It was concluded that each method has its potential. This work can help researchers choose a suitable method for fabricating thin films, depending on the aims and objectives of their work.

The structure of macrobending fiber optics is an ideal structure for constructing fiber optic sensors. This study presents a new design and implementation of U-shaped fiber optics. The basic geometric parameters of U-shaped fiber optics, such as dimension size or curve radius, are analyzed. The Taguchi method was used to optimize the effects of the control and noise factors with respect to dimension size, loop, wavelength, and core size. The control factors were varied at different levels to achieve a novel sensitivity response optimization of the wavelength and core size. The quality characteristics of the signal-to-noise ratio (larger-the-better characteristics) were used to determine the effect of the control parameters in the data analysis. The data of the sensitivity response was analyzed to predict the performance of the U-shaped fiber optics. Results indicate that, by using the Taguchi method, the best control factor setting involves 2.5 cm × 1.5 cm (dimension size) and 1550 nm (wavelength). The percentage contribution of wavelength is the highest at 67.17%, followed by dimension size (13.31%) and number of loops (11.72%) for the fiber optic core size of 50–9–50 μm. For the 9 μm single-mode fiber optics, the corresponding percentages are 61.48%, 16.64%, and 12.81% for wavelength, dimension size, and number of loops, respectively. The Taguchi methodology is suitable for designing sensor geometry.

Bending losses in optical fibers comprise one of the extrinsic attenuations that contribute to optical loss and they are essential for optical fiber bending sensor applications. This work investigated the optical loss in a standard single-mode step-index fiber optics due to fiber bending at 1550 nm wavelength. Variations in macro-bending loss with curvature radius and turn number have been measured. Curvature radius and turn number are examined for sinusoidal and elliptical shaped bending configurations. It has been found that the loss increases as the bending radius and number of turns increase. The result also showed that elliptical shaped bending configuration produced more loss in contrast to that of sinusoidal shaped at bending angles of 180° and 360°. The study on the macro-bending loss in terms of curvature radius and turn number for both elliptical and sinusoidal shaped bending configurations is beneficial for future fiber optic sensor applications.

It is difficult to produce a good film consisted of nanocrystals with good alignment. So far, a lot of methods and especially expensive vacuum-based methods have been used to produce such films. In this paper, sol gel and spin coating method were introduced. The combination of these simple and cheaper methods was used because of the high potential of those methods to produce good quality nanocrystals. First, nanocrystals were produced by sol gel method and later spin coating was done to control the thickness of the nanocrystals film. During the spin coating process, a metal tape was used to avoid solution from splashing out from the glass substrate. Subsequently, nanocrystals film was heated up from room temperature to 400 °C. To study the alignment of nanocrystals, Field Emission Scanning Electron Microscopy (FE-SEM) was used. Through this analysis, we found that the nanocrystals was in spherical pattern and the alignment of this film was well arrayed. Here, the combination of the two cheaper and simpler methods can be used to produce good quality of nanocrystals thin film and at the same time can save our research cost.