High resolution spectroscopy of ammonia in a hollow-core fiber

We have demonstrated frequency modulation saturation spectroscopy of the v(1) + v(3) band of ammonia in hollow-core photonic bandgap fibers (HC-PBFs). Previously blended lines have been resolved and the corresponding molecular transitions assigned. Cross-over resonances are observed between transitions that do not share a common level. We have measured the pressure dependence of the line shape and determined the collisional self-broadening coefficients for ammonia. The many absorption lines of ammonia in the 1.5 mu m wavelength region are potential frequency references lines for optical communication as well as candidates for spectroscopic trace gas monitoring. (C) 2008 Optical Society of America.