Part-per-trillion level trace-gas photoacoustic detection with a new racket-shaped cantilever

Trace-gas sensing at parts-per-trillion level or below, has become a hot research topic impacting daily-life applications such as human health, environmental monitoring, and security control. The scientific effort together with technological progress has enabled the possibility to reach ultra-high sensitivities also with compact and robust photoacoustic-based setups, exploiting their intrinsic high degree of flexibility with the sensitivity enhancement provided by mid-IR semiconductor laser sources and high-finesse optical cavities. In this framework, we present a study of an advanced configuration for photo-acoustic trace-gas sensors, aiming at optimizing all the key components to enable a ppt detection level. Alongside exploiting a mid-infrared continuous-wave Quantum Cascade Laser as the excitation source, a Fabry-Perot optical resonator is implemented for an efficient intracavity power enhancement. For the acoustic-to-voltage transduction an unconventional and highly performing “racket-shaped” silicon-based Micro-Electro-Mechanical System is exploited, whose oscillations are measured via a balanced Michelson interferometric readout.