Silicon-Based Racetrack Resonators: Harnessing EIT for Enhanced Near Infrared Sensing

Abstract

Silicon on insulator (SOI) waveguides are the most used waveguides in photonic components and devices, primarily because of their low losses and compatibility with complementary metal oxide semiconductor (CMOS) manufacturing. This compatibility enables the use of electronic fabrication facilities to produce photonic circuits. In SOI waveguides, most of the photonic mode is contained within the silicon core, while an exponentially decaying evanescent tail extends into the surrounding cladding. Racetrack-resonators are pivotal in advancing silicon photonics, enabling the creation of compact resonators that support high-quality factors (Q-factors). A typical racetrack resonator consists of an optical waveguide that loops back on itself, creating resonance when the optical path length corresponds to an integer multiple of the wavelength. In this paper, we introduce an optical gas sensor based on electromagnetically induced transparency (EIT), a quantum interference effect arising from the interaction of two nearby resonant modes. Our design features a double racetrack with varying radii that resonate at$1.55 \mu \mathrm{m}$. By placing the smaller racetrack inside the larger one, we achieve the EIT phenomenon, resulting in the absence of resonant spectral lines at the same wavelength and the emergence of two shifted resonance lines. This sharp and narrow transmission peak enhances gas detection accuracy, making this sensor a promising tool for environmental monitoring and industrial applications, where precise measurements of gas concentrations are essential.