High resolution spectroscopy of ammonia in a hollow-core fiber

Ana M Cubillas,Jan C Petersen,Jan Hald

doi:10.1364/oe.16.003976

Abstract

We have demonstrated frequency modulation saturation spectroscopy of the nu(1) +nu(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 microm wavelength region are potential frequency references lines for optical communication as well as candidates for spectroscopic trace gas monitoring.

Highlights

Hollow-Core Photonic Bandgap Fibers (HC-PBFs) [1] allow the confinement of high intensity light over long absorption paths
We have demonstrated frequency modulation saturation spectroscopy of the ν1 + ν3 band of ammonia in hollow-core photonic bandgap fibers (HC–PBFs)
We report the observation of FM saturation spectroscopy on selected absorption lines in the near-infrared ν1 + ν3 band of ammonia (14NH3) in a HC-PBF

Summary

Introduction

Hollow-Core Photonic Bandgap Fibers (HC-PBFs) [1] allow the confinement of high intensity light over long absorption paths. In this way, saturated absorption spectroscopy can be performed in these fibers [2,3,4,5]. We report the observation of FM saturation spectroscopy on selected absorption lines in the near-infrared ν1 + ν3 band of ammonia (14NH3) in a HC-PBF. We have observed crossover resonances between pairs of transitions that do not share a common level. This is a rather unusual phenomenon, and we argue that these are due to predominantly collisional transitions. Better knowledge of the ammonia spectrum in the 1.5 μm range is desirable for spectroscopic trace gas monitoring of ammonia [11]

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