Spectroscopy of optically pumped ammonia and deuterium oxide near 1 THz
Molecular gases like ammonia (NH<inf>3</inf>) and deuterium oxide (D<inf>2</inf>O) can be used as active media for optically pumped terahertz lasers (OPTL). In this paper we present spectroscopic measurement of chosen NH<inf>3</inf> and D<inf>2</inf>O lasing lines near 1 THz. Rotational-vibrational transitions are pumped by mid infrared quantum cascade laser (MIR QCL) which offers more precise tunability in MIR spectral range than standard optical pumping methods (CO<inf>2</inf>, N<inf>2</inf>O lasers). This allows to access new lasing lines. Frequency domain measurements of NH<inf>3</inf> and D<inf>2</inf>O under different pressure, pumping frequency and pumping power are performed. The results show high gain obtained for NH<inf>3</inf> (3,3) line at 1.073 THz and very low gain for D<inf>2</inf>O (4,3,2) line at 533 GHz due to the low population.
New cw far-infrared D2O, 12CH3F and 14NH3 laser lines
Far infrared cw laser emission was obtained from D 2 O and 14 NH 3 by optical pumping with sequence band CO 2 -laser lines. In addition a new FIR laser line was excited in 12 CH 3 F. The pump and FIR laser transitions have been assigned.
Submillimeter Emission from Optically Pumped 14NH3
A CO2 TEA laser was used for optical pumping of 14NH3. Thirteen CO2 lines, which deviate by 0.05 cm-1 or less from transitions in 14NH3, were effective in producing submillimeter laser transitions. Most of the 24 emitted lines have wavelengths between 70 and 400 μm and represent rotation-inversion transitions in the ν2 state of NH3. A few short wavelength lines (30-70 μm) are 2ν2 transitions obtained by pumping from the ν2 state. The influence of pressure, resonator length and outcoupling on the appearance of the submillimeter lines was investigated. The choice of parameters was not critical for observing the lines, which in general had high gain. Each pump pulse delivered 1-50 mJ in 150 ns to the NH3 gas. Some submillimeter lines persisted up to an NH3 pressure of 30-70 torr or to 300-400 torr in a mixture of NH3 and He.