Abstract
Source identification and accurate measurements of methane gas
concentration are key tools necessary for climate change management.
Here we present a method for methane isotopologue ratio measurement
using a laser-based frequency modulation (FM) spectroscopy technique
in the near infrared at 1661 nm. We provide line shape analysis
and discuss a fitting algorithm for accurate isotopologue ratio
metrology and investigate and minimize the effects of residual
amplitude modulation on the experimentally produced FM signal line
shape. This FM technique is further evaluated for future development
of a cavity-enhanced and noise-immune system capable of isotopologue
ratio as well as ultrasensitive trace gas measurements, all accessible
using a single distributed feedback laser.
Funder
Department for Business, Energy and
Industrial Strategy, UK Government
Subject
Atomic and Molecular Physics, and Optics,Statistical and Nonlinear Physics