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 Title: Optically-pumped Ammonia Terahertz Laser Up To 5.5 thz Author(s): Mammez, Marie-Hélène Contributor(s): Roy, P.; Pirali, Olivier; Martin-Drumel, Marie-Aline; Barbieri, Stefano; Eliet, Sophie; Lampin, Jean-François; Mouret, Gaël; Hindle, Francis Subject(s): Instrument/Technique Demonstration Abstract: Optically-pumped molecular THz lasers are powerful and versatile sources. We have demonstrated a continuous wave molecular laser emission based on ammonia (\ce{NH3}) optically pumped by a quantum cascade laser at about 1 THz \footnote{A. Pagies, G. Ducournau, and J.-F. Lampin, “Low-threshold terahertz molecular laser optically pumped by a quantum cascade laser,” APL Photonics, vol. 1, 031302, 2016.}. The purpose of this work is to investigate \ce{NH3} laser transitions at higher frequencies. This molecule is pumped by the pump laser from the ground state to the $v_2 = 1$ vibrational state. Within the excited state, two types of THz transitions can occur in this molecule: pure inversion transitions and rotation-inversion transitions. Inversion motion is a particular quantum phenomenon of the \ce{NH3} molecule that splits the energy levels: the N atom is able to tunnel through the potential barrier formed by the three H triangle. The inversion splitting is about 1 THz in the $v_2 = 1$ state but rotation-inversion transitions can be used to generate higher frequencies. The investigation of molecular laser shows a lack of available databases of potentially lasing transitions for users to exploit. We propose a molecule dependent figure of merit which enables to discriminate potentially lasing transitions by their lasing potential. We report here its use to predict lasing lines of ammonia. The demonstration of its pertinence is made by observing 32 lasing lines of \ce{^{14}NH3} and 5 lines of \ce{^{15}NH3} up to 5.5~THz. This work is supported by the ANR project HEROES (ANR-16-CE30-0020), the “Photonics for Society” CPER and the Interreg project TERAFOOD. Issue Date: 2021-06-22 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/111199 Date Available in IDEALS: 2021-09-24
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