Simultaneous multispecies gas sensing by use of a sampled grating distributed Bragg reflector and modulated grating Y laser diode.

Widely tunable laser diodes operating at 1520 < or = lambda < or = 1570 nm are characterized and compared for use as sources for tunable laser diode gas absorption spectroscopy. Three gases, hydrogen cyanide, ammonia, and acetylene, with overlapping absorption features within the 50 nm tuning range of the devices were targeted by use of wavelength modulation spectroscopy with second-harmonic detection. In addition, a method for modulating the laser to improve sensitivity by taking advantage of the unique structure of these devices is reported.