Photonic crystal with multiple-hole defect for sensor applications

A photonic crystal defect consisting of several subwavelength holes was investigated as a means to increase the surface area of the defect region without compromising the quality factor of the structure. Finite-difference time-domain calculations were performed to determine the relationships between the size of the multi-hole defect (MHD) region, resonance frequency, quality factor, and refractive index of the defect holes. The advantage of using the MHD for sensing applications is demonstrated through a comparison with a single hole defect (SHD) photonic crystal structure. Assuming the same monolayer thickness of biomaterial coats the defect hole walls of the MHD and SHD, the MHD has a three times larger change in resonance frequency and two times larger quality factor.