New widely tunable mid-IR lasers and their use in molecular spectroscopy

James Jeffers; Patrick J. McCann; Khosrow Namjou; Chad Roller; Zufan Debebe; Joe Grego

doi:10.1117/12.455160

7 February 2002 New widely tunable mid-IR lasers and their use in molecular spectroscopy

James Jeffers, Patrick J. McCann, Khosrow Namjou, Chad Roller, Zufan Debebe, Joe Grego

Proceedings Volume 4574, Instrumentation for Air Pollution and Global Atmospheric Monitoring; (2002) https://doi.org/10.1117/12.455160
Event: Environmental and Industrial Sensing, 2001, Boston, MA, United States

Abstract

Newly available mid-infrared lasers made from IV-VI compound semiconductors exhibit tuning ranges of over 200 cm^-1. In addition to allowing detection of a variety of species with a single laser, such wide tunability enables detection of large molecules with broad absorption bands. This paper presents results from detailed measurements of IV-VI diode laser emission obtained using an automated Fourier transform infrared (FTIR) spectroscopic testing system. Single mode emission wavelengths were determined for different combinations of heatsink temperature and injection current. These data were then used to design and perform molecular spectroscopy experiments in which laser emission wavelength was modulated by either current or temperature tuning. Current tuning over narrow spectral regions (up to 3 cm^-1) allowed detection of various small to medium sized molecules such as carbon disulfide, ammonium hydroxide, and benzene, but failed to detect larger molecules such as toluene. We show that temperature tuning a IV-VI laser over at least 50 cm^-1, however, can enable detection of large molecules such as toluene and improve the detection sensitivity of medium sized molecules such as benzene. This new technique extends the use of mid-infrared laser spectroscopy to measurement of large molecules that do not have resolvable ro-vibrational structure.

Citation Download Citation

James Jeffers, Patrick J. McCann, Khosrow Namjou, Chad Roller, Zufan Debebe, and Joe Grego "New widely tunable mid-IR lasers and their use in molecular spectroscopy", Proc. SPIE 4574, Instrumentation for Air Pollution and Global Atmospheric Monitoring, (7 February 2002); https://doi.org/10.1117/12.455160

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