Optical ‘nose’ now detects multiple molecules

Building on earlier work in noise-immune cavity-enhanced optical-heterodyne molecular spectroscopy (NICE-OHMS) for the ultrasensitive detection of trace gases and other molecules through detection of single absorption features (see www.laserfocusworld.com/articles/219797), researchers at JILA (Boulder, CO) can now detect and distinguish multiple molecules within a sample at high sensitivity levels by recovering multiple absorption features simultaneously over many parallel channels spread across a broad spectral range.

The improvement uses an ultrafast-laser-based optical frequency comb for broadband molecular detection (100 nm around the 800 nm center wavelength of the laser source) in many parallel channels, with sensitivity values of 0.01 ppm and real-time data acquisition at speeds of 1 ms per 15 nm of bandwidth. Though cavity-ring-down spectroscopy (CRDS) offers comparable sensitivity, its bandwidth and acquisition time is limited to the tuning ability of the laser and serial acquisition speeds of the system. The JILA scientists are implementing a portable version of the system that can reach 1 ppb sensitivity levels over an even broader bandwidth range. Contact Jun Ye at [email protected].