Quartz-Enhanced Photoacoustic sensors for H2S trace gas detection

We report on three different quartz enhanced photoacoustic (QEPAS) sensors operating in the near-IR, mid-IR and THz spectral ranges, employing quartz tuning forks of different sizes and shapes. To test our sensors in the near-IR we used a diode laser working at 2.7 mu m, while in the mid-IR we employed a quantum cascade laser (QCL) operating at 7.9 mu m, fiber-coupled to the QEPAS cell. In the THz range we employed a QCL emitting at 2.91 THz. H2S absorption features with line-strength up to similar to 10(-21) cm/mol were selected and QEPAS normalized noise-equivalent absorption in the 10(-9) W center dot cm(-1)center dot Hz(-1/2) range was achieved.