Sensor design base on slow light in photonic crystals

Controlling and managing the propagation of light is one of the important issues in optics and photonics. Many properties of light enable high precision sensor designs. The use of photonic crystals in these sensor designs has become widespread in recent years. Photonic crystals are structures that have a photonic band gap, similar to the electronic band gap in semiconductors, where the dielectric constant changes periodically in one, two, or three dimensions. While this photonic band gap allows certain wavelengths to travel through the crystal, it prevents certain wavelengths from moving through the crystal by reflecting them back. With the intentional defects created in photonic crystal structures, defect modes in the photonic bandgap are obtained. As these defect modes travel through the waveguide, the increasing substance-field interaction as a result of the decrease in the group velocity increases the sensitivity of the sensor. In this thesis study, the design of square lattice photonic crystals is made and the changes on the properties of the photonic crystals are investigated. The group velocity of the light is reduced by various changes made in the lattice symmetry of the photonic crystal, and as a result, the matter-field interaction is increased. With the design, the group velocity of the light is calculated as 0,13 * c and the sensor sensitivity is obtained as 212 nm / RIU. Two different modes are examined in the second design, which is designed to investigate the effect of higher-order modes on sensor sensitivity. In the second design, 166 nm / RIU sensor sensitivity is reached with the first mode and 181 nm / RIU with the second mode. In this design, it has been shown that the concentration of the evanescent field on the dielectric rods increases the sensitivity of the sensor.