Optical Dispersion: Variation of Refractive Index of Polypyrrole and SnO2 Nanocomposite Thin Film with Incident Wavelength

In this study, we investigated the dielectric properties of nanocomposite thin films using surface plasmon resonance. The aim was to understand how the excitation wavelength affects the refractive index dispersion curve and to determine the suitability of these films for various applications. Our findings suggest that these nanocomposite thin films exhibit promising dielectric properties and could be useful in optical and electronic devices. The variation in wavelength shows dispersion of the dielectric properties of the prepared thin films. The technology of surface plasmon resonance (SPR) has been mostly exploited in angular interrogation mode using monochromatic laser light at a fixed incident wavelength. This in turn generated information about the complex dielectric constant and refractive index of the dielectric material coated above the metal surface. In the present communication, we present the refractive index dispersion of the prepared composite thin film. A red laser light of wavelength approximately 633 nm and TM polarisation is exploited to illuminate the sample surface, and the corresponding reflectivity spectra are recorded by the spectrometer. A complete SPR reflectance curve can be observed by varying the angular plasmonic coupling conditions, and a complete reflectivity surface R( , ) can be measured. After measuring the experimental SPR data, the complex dielectric constant and refractive index are calculated by fitting them with the theoretical Fresnel equations. In order to do this, a sample of polypyrrole (PPy) and tin oxide (SnO2) nanocomposite thin films is prepared by sol-gel and spin coating techniques over a gold-coated prism. The dielectric properties were examined by varying the excitation wavelength of the source in the visible range. The refractive index dispersion curve was plotted and fitted with the Sellmeier equation to analyze.