Electromagnetically induced transparency-based optical gas sensor using plasmonic corrugated ring resonators

The proposed optical gas sensor is based on the principle of electromagnetically induced transparency (EMT), which is a quantum interference phenomenon that occurs when two closely spaced resonant modes interact with an intermediate level. In our design, we use plasmonic corrugated ring resonators that resonate in the mid-infrared (MIR) wavelength range, which is of particular interest because it contains the absorption resonance for several gas molecules such as methane, carbon dioxide, carbon monoxide, and acetone. We propose a slotted waveguide coupled with a slotted corrugated ring resonator, which is etched inside a doped silicon wafer on sapphire. Doped silicon is a better alternative to noble metals for plasmonic techniques in the MIR region. By optimizing the corrugated and ring to resonate at the same wavelength, we observe interesting phenomena such as Fano-resonance and EIT effects. The EIT effect causes the absence of resonant spectral lines at the same wavelength and the creation of two resonance lines at red-shifted and blue-shifted wavelengths. This effect is useful in gas sensing because it provides a sharp and narrow transmission peak that enables precise detection of gas molecules. In our paper, we provide details about the dimensions and materials used in our design. We demonstrate that our sensor achieves a small footprint, high sensitivity, and high Figure of merit. The small footprint makes our sensor suitable for integration into compact devices, while the high sensitivity and Figure of merit make it ideal for accurate and reliable gas sensing applications.