Molecular Dispersion Spectroscopy Using a Code-Division-Multiplexed Optical Carrier

Abstract

A fiber-optic molecular dispersion spectrometer using code-division multiplexing to make simultaneous phase measurements of a hydrogen cyanide (${\mathrm{H}}^{13}{\mathrm{C}}^{14}\mathrm{N}$) $2{\ensuremath{\nu}}_{3}$-band P10 rovibrational transition at multiple optical frequencies is demonstrated. A second-derivative anomalous dispersion response is digitally synthesized from sets of these concurrent measurements. The synthesized measurement demonstrates 3 orders of magnitude noise suppression relative to individual measurements, has intrinsic wavelength tuning linearization, and a spectroscopic detection limit of $146\phantom{\rule{0.2em}{0ex}}\mathrm{ppb}\phantom{\rule{0.1em}{0ex}}\mathrm{m}/\sqrt{\mathrm{Hz}}$.