Detection of HCI at the ppb Level with a DFB Laser Based Spectrometer

Abstract

In several industrial processes there is a growing demand for a fast and sensitive detection of HCl, in order to reduce the pollution due to that molecule. We realized a compact spectrometer based on distributed feed-back (DFB) diode laser, which adopts a two-tone frequency modulation technique, for reaching a detection limit of few ppb. This technique moves the demodulation frequency in a region where the laser excess noise can be reduced to a lower level (10 MHz - 1 GHz).