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21THz-O-2
Nanosecond pulsation of THz NH3 laser emission under optical pumping by "long" 100 ^s) CO2 laser pulses
A.A. Ionin1, I. O. Kinyaevskiy1, Yu.M. Klimachev1, D.I. Kormashova1, A.A. Kotkov1, A.A.
Kozlov1, J.-F. Lampin2, Yu.A. Mityagin1, S.A. Savinov1, A.M. Sagitova1, D.V. Sinitsyn1, M.V.
Ionin1
'P.N. Lebedev Physical Institute of the Russian Academy of Sciences, 53, Leninskiy Prospekt, Moscow, 119991
2Institute of Electronics, Microelectronics and Nanotechnology, Cité Scientifique, Avenue Henri Poincaré,
59652 Villeneuve d'Ascq Cedex,, Lille, France
klimachevym@lebedev.ru
Generation of a terahertz NH3 laser with optical pumping by "long" (~ 100 ps) pulses of an electron-beam-sustained discharge (EBSD) CO2 laser was for the first time implemented, the NH3 laser pulses and "long" CO2 pump laser pulses being measured simultaneously with nanosecond resolution. We used an optical pumping scheme similar to one used in [1]. The time delay of the NH3 lasing onset decreased, and the laser pulse duration went up with CO2 laser pulse energy growth. Experimental results for the NH3 laser and CO2 laser pulses are demonstrated in Figs. 1 and 2 (ammonia pressure 4.5 mbar). The inserts in the Figures show the initial parts of the laser pulses. The temporal shape of the CO2 laser pulses was calibrated to the measured values of the pulse energy E. The time instant t=0 corresponds to the beginning of the EBSD pulse, the duration of which is ~ 50 ps.
Fig. 1. Pulses of the CO2 laser (bottom) and NH3-laser (top) pumped by 9R(16) line. £=0.59 J.
Fig. 2. Pulses of the CO2 laser (bottom) and NH3 laser (top) pumped by 9R (30) line. £=0.91 J.
The terahertz lasing was observed during the most powerful part of the CO2 laser pulse, when the pump peak power on 9R(16) line exceeded -15 kW, and on 9R(30) line - 25 kW. It can be seen from Fig. 1, that the NH3 laser pulse shape follows the shape of the most powerful part of the pump pulse. In Fig. 2 two pronounced maxima in the terahertz pulse under the sufficiently stable CO2 laser emission are observed. We assume that this fact is just a demonstration of the cascade mechanism of NH3 lasing, which was proposed to explain the multifrequency lasing under pumping by 9R(30) CO2 laser line. The terahertz NH3 laser wavelengths were also measured. When the NH3 laser was pumped by 9R(30) CO2 laser line, the wavelengths turned out to be 67.2, 83.8, and 88.9 pm. The strongest of the observed lines was the spectral line at 83.8 pm. When the NH3 laser was pumped by 9R(16) line of the EBSD CO2 laser, of the all possible NH3 lasing lines only the line with the wavelength of 90.4 pm was recorded. The dependence of the NH3 laser energy versus pump energy for various ammonia gas pressures is also discussed.
This research was supported by the Russian Foundation for Basic Research (Project 18-52-16019).
[1] Nishi Yo., Horiuchi Ya., Wada S. et al. // Japanese J. of Applied Physics 1982. V. 21. P. 719.
