Simulation and Fabrication of a Photonic Crystal Transmission Filter for Biosensing Applications

Abstract

Photonic crystals are artificial materials with periodicity in the dielectric function on the sub-micron scale. They can exhibit extraordinary light confining properties superior to other known materials, making them attractive for photonic devices. Among many potential applications, the use of photonic crystals as biosensors in clinical settings has drawn significant attention lately. In this work, photonic crystal structures are designed and simulated in two and three dimensions. The photonic crystal structure used as a basis is a hexagonal pattern of cylindrical air holes in a silicon slab. Different designs of cavity transmission filters are investigated, and the application of these filters as biosensors is investigated through simulations. Based on the simulation results, devices are fabricated with relevant nanofabrication techniques. The fabrication process of photonic devices is further optimized. For the first time at NTNU, functioning photonic crystal transmission filters are fabricated, with quality factors of around 10^3 , which is of similar order as the highest reported values for similar structures. Through simulations, the application of a biolayer to the photonic crystal surface is found to give a shift in resonance frequency that is of sufficient magnitude to be detected. Further work could be done to improve the performance of the sensors, but the findings in this thesis support the belief in photonic crystals, and particularly transmission filters, as a promising platform for biosensing applications.