Systems and methods for measuring trace contaminants in gas matrix using integrated cavity output spectroscopy

A laser absorption spectrometry system for gas measurement, comprising:

• an integrated cavity output spectroscopy (ICOS) assembly comprising:
• a gas cell comprising a cell body defining an optical cavity;
• three or more tunable diode lasers having three or more nominal wavelengths and configured to emit three or more laser light in three or more wavelength ranges, the three or more wavelength ranges corresponding to absorption ranges of three or more different contaminants in gases;
• and
• a combiner configured to multiplex the three or more laser light into a combined laser light configured to be coupled into the optical cavity, the combined laser light having the three or more wavelength ranges,
• wherein the ICOS assembly further comprises a reflective collimation mirror positioned in an optical path between the three or more tunable diode lasers and the gas cell, the reflective collimation mirror configured to reduce noise from etalons, wherein when light travels back and forth between parallel surfaces and/or quasi-parallel surfaces in the optical path, the light and its reflection interfere with one another and cause the etalons, the etalons introducing the noise in absorption spectra of the light by the gases in the gas cell, and
• wherein the three or more tunable diode lasers comprise a first tunable diode laser configured to emit first laser light in a wavelength range corresponding to a first contaminant in the gases and a second tunable diode laser configured to emit second laser light in a wavelength range corresponding to a second contaminant in the gases.