Wavelength modulated multiheterodyne spectroscopy using Fabry-Pérot quantum cascade lasers.
Multiheterodyne spectroscopy implemented with semiconductor Fabry-Pérot lasers is a method for broadband (> 20 cm-1), high spectral resolution (~1 MHz) and high time resolution (< 1 µs/spectrum) spectroscopy with no moving parts utilizing off-the-shelf laser sources. The laser stabilization approach demonstrated here enables continuous frequency tuning (at 12.5 Hz repetition rate) while allowing for multiheterodyne wavelength modulation spectroscopy (WMS). Spectroscopic detection of N2O around 1185 cm-1is experimentally realized, which shows a direct absorption sensitivity limit of ~1.5⨯10-3/√Hz fractional absorption per mode. This can be lowered using WMS down to 5⨯10-4/√Hz per mode, limited by optical fringes. This approaches the range of sensitivities of standard single-mode laser based spectrometers, which demonstrates that the multiheterodyne method is well-suited for chemical sensing of spectrally broadened absorption features or for multi-species measurements.
Andreas
A
Hangauer
Jonas
J
Westberg
Eric
E
Zhang
Gerard
G
Wysocki