Optical microcavities based on anodic titania

Cyclic anodizing is an advanced method for synthesis of periodic porous structures, such as photonic crystals, heterostructures, and optical microcavities (OMs). These structures have a wide range of applications in sensing, nanophotonics, and lasing. However, OMs based on anodic titanium oxide (ATO) have not been synthesized to date. Here, optical microcavities based on anodic titanium oxide (ATO) have been prepared for the first time by cyclic anodizing of titanium with a voltage versus charge modulation using a phase shift of π after half the number of cycles to form a defect in the periodic modulation of an effective refractive index of the ATO. The structure and optical properties of ATO OMs were studied by scanning electron microscopy and optical spectroscopy. The wavelength position of resonance bands of ATO OMs is in the range of 390–1640 nm and is defined by a charge density per anodizing cycle. The quality factor of the fabricated OMs is up to 16.2, which exceeds the best value reported for ATO-based photonic crystals in the literature.