Fiber laser intracavity absorption spectroscopy of ammonia and hydrogen cyanide in low pressure hydrocarbon flames

Fiber laser intracavity spectroscopy (FLICAS) with Er-doped fiber laser has been applied for the first in situ detection of ammonia and hydrogen cyanide in a low pressure (30 Torr) stoichiometric methane/nitrogen/oxygen flame doped with 0.13–1.36% of NH3. High resolution spectra of NH3 and HCN have been recorded in the range of 1.5 μm (6440–6540 cm−1). The minimum detectable concentration of HCN and NH3 at a laser pulse duration of 8 μs and room temperature is 1 × 1013 molecule/cm3. The method can be used for in situ detection of many other molecules in the hostile combustion environment.