Effective scattering area on coated glass substrates using optical side coupling technique for sensitivity enhancement

• Main Author: Jahava, Marlina
• Format: Thesis
• Language: English; English
• Published: 2025
• Subjects: T Technology; TA Engineering (General). Civil engineering (General)
• Online Access: http://eprints.utem.edu.my/id/eprint/29316/

The integration of nanomaterials with optical sensing platforms has significantly advanced the performance and versatility of sensor devices. Among various alternatives to optical sensor, glass substrates have recently garnered considerable interest due to their stability, low cost, and ease of fabrication. However, conventional glass based sensors often suffer from limited sensitivity, primarily due to inefficient light coupling and low transmission from a single edge illuminated source. This research proposes an enhanced optical sensing approach utilizing side coupling visible light on a zinc oxide (ZnO) nanorod coated glass substrate. By directing a visible light source perpendicularly onto the upper surface of the glass, the technique increases light intensity along the sensing region while minimizing backscattering losses. ZnO nanorods, selected for their high refractive index, were coated on the substrate surface. Different exposed coating areas were investigated to evaluate their influence on light scattering and coupling efficiency. Experimental results demonstrate that a sensor with a 0.022m² coating area achieved superior performance across multiple parameters, including output light intensity, voltage response, and refractive index sensitivity. This sample exhibited a 97.5% linearity and a sensitivity of 0.0125V/%Concentration, outperforming single-source devices by a factor of 1.5. The proposed sensor also showed notable improvements in resolution and linear range, indicating its potential for high precision optical measurements. Overall, this study introduces a simple yet effective method for enhancing the performance of glass based optical sensors. By leveraging the scattering and absorption characteristics of ZnO nanostructures under side-coupled illumination, the proposed design offers a promising solution for developing reliable and cost efficient sensors suitable for various industrial and environmental monitoring applications.