Subwavelength Electromagnetic Confinement

A dielectric-based grating structure is designed and it is capable of tightly focusing the radiation at the point of interest. The design parameters for the dielectric structure are obtained from the optimal solution achieved by running the genetic algorithm within the given constraints. The optimization is carried out in a clustered environment where the dielectric structure is simulated in MEEP, an open source FDTD package to determine the electric and magnetic field patterns. The strong confinement of radiation with the presence of dielectric grating structure is evident from the time domain results. The near field time-domain results are transformed to frequency domain to obtain the far-field radiation pattern for the designed dielectric structure. This illustrates that the radiation pattern steers toward the end-fire view from the broadside view of the dipole pattern. The effect of radiation enhancement is also observed by calculating the Purcell Factor (PF) with the presence of the dielectric structure. Due to its high spontaneous emission, there is significant reduction in lifetime of atoms leading to full radiative decay resulting in 100% quantum efficiency. This designed dielectric grating can be easily fabricated and embedded with optical devices due to its planar form giving it a competitive advantage over its peers.