The PolySense and Polysense Innovations teams have just published a new article on Photoacoustics Journal Elsevier (IF 6.8) reporting on a Quartz-Enhanced Photoacoustic Spectroscopy sensing technique based on single-laser dual-frequency superimposed modulation. By simultaneously injecting two independent high-frequency modulation signals, matching the fundamental and overtone resonance modes of a Quartz Tuning Fork(QTF), into a single Distributed Feedback laser, dual-channel real time synchronous detection is achieved within a compact single path optical architecture. A comprehensive physical model incorporating both Residual Amplitude Modulation and high order non-linear competition effects has been proposed. We demonstrate that the fourth derivative of the gas absorption line shape plays a dominant role in inducing signal suppression and waveform splitting under strong dual-frequency modulation. A waveform optimization strategy based on dynamically tuning the laser scanning rate allow to regulate the effective filtering behavior of the lockin amplifier.
The following link provides access to the article:
http://polysense.poliba.it/wp-content/uploads/2026/06/1-s2.0-S2213597926000492-main.pdf
