Photoacoustic methane detection using a novel DFB-type diode laser at 3.3 μm

To the best of our knowledge, we present for the first time spectroscopic methane measurements using a laser diode at 3.3 μm operated in continuous mode at room temperature. The DFB-type laser emits a maximum optical output power of 1.5 mW with a spectral linewidth below 10 MHz. This novel kind of semiconductor laser allows precise photoacoustic measurements of characteristic methane absorption structures in the ν3 band. In addition, the setup enables a detection limit below 1 ppm.