Gas cell

Gas molecules have intra-molecular movements such as vibrational, rotational and translational motions, which absorbs energy in the THz frequency range. Another reason to use THz radiation for gas sensing is that it is non-invasive and non-ionizing, which provides application potentials in sensitive industrial environments. We build a continuous wave THz gas sensing system which implements a Y-DBR two-color laser (a MOPA laser from FBH) for coherent generation and detection of THz waves, and a multipass gas cell made of stainless steel for gas measurements. The difference frequency from the two-color emission can be tuned either by current or by temperature. With water vapor as out first gas sample, we demonstrated a water absorption line near 557 GHz, which corresponds to the transition lines provided by the HITRAN database. Further research is being carried on to further improve the resolution and measurement speed for fulfilling the industrial requirements.