Optical Sensors Based on Photonic Crystal

Abstract

In recent years, photonic crystals have achieved a lot of research significance due to their applications in many fields. Many photonic ccrystal sensors have been proposed based on their novel structure and unique physical properties such as reflectance/transmittance. In this thesis, two layers one dimensional photonic crystal slab waveguide was assumed in which the first layer was considered to be the analyte layer and the second layer was considered to be LHM, dielectric or metal for transverse electric (TE) and transverse magnetic (TM) waves. The dispersion relation of the proposed structure was derived and solved numerically and the sensitivity was also calculated. The condition required for the sensor to have its maximum sensitivity were presented. The dependence of the sensitivity on some different parameters of the structure was plotted and studied. It was found that the highest sensitivity was achieved by using the LHM materials in the photonic crystal rather than using metal and dielectric materials in photonic crystal. Our results show that it is possible for LHM photonic structure to achieve a sensitivity improvement of 412% for TE mode and 1056% for TM mode when compared to conventional slab waveguide sensor. Moreover, one dimensional ternary photonic crystals were investigated as refractometric sensors for sensing very small refractive index change of an analyte material. The principle of operation of photonic crystal as a refractometric sensors in reflection mode was explained. The transmission of an incident wave were studied in details using Fresnel reflection coefficients. The transmission coefficient was plotted with the angle of incidence and wavelength of incident light for air and water as analyte materials. It was observed that a slight refractive index change in analyte layer of the ternary structure causes a sufficiently large transmission peak shift.