Experimental Demonstration of a Plasmonically-Enhanced Vacuum-Packaged LVR-Based Gas Sensor

This work proposes the combination of a microelectromechanical system (MEMS)-based spectrally-selective uncooled thermal infrared (IR) detector with an IR spectroscopic multipass gas cell to enable new applications like the remote monitoring of the concentration of atmospheric trace gas molecules through direct laser absorption spectroscopy (LAS) on novel sensing platforms such as drones. In particular, due to its increasingly concerning impact as a greenhouse gas, N<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>O was selected as the target molecule for this experimental demonstration, and a final sensitivity of around 5.4 Hz/ppm was assessed. The enabling technology consists of a 30% doped ScAlN laterally vibrating resonator (LVR) integrated with spectrally selective metal-insulator-metal (MIM) plasmonic metamaterial absorbers. After being vacuum packaged, it has been experimentally characterized, resulting in a responsivity of 0.3 Hz/nW and a NEP of 500 pW/Hz<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1/2</sup>. These performances exceed by more than two times and a half the ones of the same LVR without absorbers, thus demonstrating the potential improvements that this approach can lead to.