This study presents the design and analysis of a one-dimensional photonic crystal (1D-PC) composed of alternating layers of SiO₂ and air, engineered to function as a tuneable optical filter based on temperature and frequency variations. The proposed structure leverages the unique optical properties of SiO₂, such as its high refractive index and thermal stability, combined with the low refractive index of air to create a photonic bandgap (PBG) that can be dynamically adjusted. By exploiting the thermo-optic effect of SiO₂, the refractive index of the material is modulated in response to temperature changes, enabling precise control over the PBG and, consequently, the filtering characteristics of the device. Additionally, the frequency-dependent response of the 1D-PC is investigated, demonstrating its ability to selectively transmit or block specific wavelengths of light. Numerical simulations and theoretical modelling are employed to optimize the layer thicknesses and periodicity of the structure for enhanced performance. The results indicate that the proposed 1D-PC can serve as an efficient tuneable filter for applications in optical communication, sensing, and photonic integrated circuits, offering a versatile solution for dynamic wavelength management in response to environmental and operational conditions.

Photonic Crystal, Photonic Band Gap, Filter, Tunable, Frequency