LASER EMISSIONS FROM CO2 VIBRATIONAL TRANSITIONS IN A LOW TEMPERATURE SUPERSONIC FLOW EXCITED BY A PULSED ELECTRON BEAM STABILIZED DISCHARGE
Résumé
High power long pulse infrared laser emission has been achieved on CO2 molecule with the high density and very low temperature supersonic flow-electron beam-stabilized discharge excitation device developped at I.M.F.M. ([MATH] [MATH] 2 amagats, T [MATH] 70 - 150 K). Laser emission at [MATH] = 10.6 µ has been achieved for a resonant cavity set at the discharge location and also 3 cm downstream of the discharge location. With Ar/CO2, Ar/CO2/H2, He/CO2, and He/CO2/N2 mixtures, lasing energy and power were several times higher at low temperature when experiments were performed at the discharge location. Time variation of laser power was very different compared to the room temperature, no flow, case for the same density and excitation energy. When the resonant cavity was set 3 cm downstream, outside of the discharge, lasing in the infrared was observed during several tens of microseconds for He/CO2/N2 mixtures in supersonic flow. Experimental results are presented for both characterisation of 10.6 µ laser emissions and research of lasing at longer wavelength on CO2 molecule, on the 14µ (100-010) and 16µ (020-010) cascade transitions and 18.4 µ (03 0-10 0) transition which are generally favored by very low translational temperature. Implications of I.M.F.M. results for development of high average power high repetition rate infrared laser sources useful for photochemistry are discussed.
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