Fabrication of voxelized chirel nanophotonic devices with circular dichroism

Abstract

Chirality is a commonly found property in objects and light waves. An object with an asymmetric geometry has the property of chirality, in which its image cannot be superposed on itself. Circularly polarized light waves come in the variants of left-handed and right-handed polarization, which correspond to their chiral geometry. When circularly polarized light interacts with a chiral structure, the light absorbed will have a differential variation based on the handedness of the wave, known as the circular dichroism (CD). For this project, a voxelized titanium-dioxide (TiO2) structure is fabricated for the purpose of producing a significantly noticeable circular dichroism. A TiO2 substrate is patterned with an array of 100 nm by 100 nm voxels with varying heights to produce an asymmetric structure. The asymmetry found in the array basis defines the chirality of the structure and produces a variation in the output’s intensity. This intensity variation is what determines the CD of the device. The fabrication of this voxelized array is a continuation of the ideas found in the lab’s previous work on voxelized topology optimization. The fabrication of a passive chiral-nanophotonic structure with a large CD has potential to serve as an optical polarization filter and a wavelength selector for superposed waves.