Journal of Optics

, Volume 46, Issue 2, pp 122–131 | Cite as

A set up to detect the absorption lines of atmospheric gas molecules

  • Sinan Al-Jalali
  • Moustafa Sayem El-Daher
Research Article


Due to the importance of carrying out practical and accurate measurements of atmospheric gases, we built and characterized a system to detect the absorption lines of these gases. The proposed set up consists of tunable diode laser with an external cavity designed by Littrow configuration (TDL) as light source, multipass cell with absorption path length of 30 m, and a monochromator with photomultiplier tube as detector. In this work we did not adjust the laser to emit in a single mode to get maximum number of absorption lines within scanning range simultaneously. The used setup gives us the possibility for changing few parameters for tuning the diode laser which gives clear advantage of commercial equipment with limited tunability. Due to its important environmental role we investigated CO2 absorption lines in the weak band of IR region near 1600 nm, as a test case for using the proposed set up. Despite the fact that absorption lines of CO2 near 1600 nm are weak using the proposed setup we were able to reliably detect them with a good accuracy when compared to known theoretical and experimental results listed in literature and databases as HITRAN 2008 database.


Atmosphere gases CO2 gas Tunable lasers Infrared spectroscopy Absorption spectroscopy Atmospheric gases 


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Copyright information

© The Optical Society of India 2016

Authors and Affiliations

  1. 1.Laser Spectroscopy Laboratory, Higher Institute for Laser Research and ApplicationsDamascus UniversityDamascusSyria

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