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Advanced gas sensing applications above 3 μm enabled by new DFB laser diodes

Lars Nähle , Dr. Lars Hildebrandt, Dr. Marc Fischer, nanoplus GmbH


nanoplus expands the wavelength range of application-grade monomode lasers for use in gas spectroscopy beyond 3 μm. Especially important for the monitoring of hydrocarbons, real-time sensing applications with formerly unattained accuracy become feasible with the new laser sources.

A very versatile technique for the detailed characterization of gas compositions is provided by Tunable Diode Laser Spectroscopy (TDLS). The types of constituents and their concentrations, for example, can be determined with high accuracy by making use of the unique absorption features of each gas species. Applications of laser diode based gas sensing range from human breath analysis to efficient fire detection and even gas sampling on space missions ( from these significant social and medical uses, industrial process control has evolved into one of the most important fields of application for TLDS.

With the possibility of in-situ monitoring of a process, efficient adjustment to the crucial process parameters can be performed. TLDS is however critically dependent on the availability of suitable laser sources for the designated applications. Monomode distributed feedback (DFB) diode lasers in the near infrared (NIR) wavelength range up to around 3 µm have successfully been used in a multitude of industrial applications in the past. Technologically relevant gas species in those applications included H20, CO, CO2, and NH3, for example. Application-grade monomode lasers for TDLS beyond the 3 μm limit had - until recently - been unavailable, posing a severe limitation for sensing applications especially considering the detection of hydrocarbons.

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