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.
IR Vibration-Rotation Spectra of the Ammonia Molecule
The IR spectrum of the ammonia inversion vibration-rotation normal mode is obtained using Fourier Transform IR Spectroscopy and analyzed using Maple, to easily obatin the relation between the N-H bond length and the H-N-H bond angle. As expected, the absolute geometry of the ammonia molecule cannot be determined completely with information gleaned from this vibrational transition.
Intense superradiant emission at 496 μm from optically pumped methyl fluoride
Intense superradiant emission has been observed from methyl fluoride excited by 0.6‐MW pulses from a high‐pressure CO2 laser. Pulses of ∼ 1 kW with a duration of ∼ 150 nsec have been obtained from a 5‐m‐long 40‐mm‐diam cell containing 0.7 Torr of methyl fluoride. This output represents an efficiency of converting infrared photons to far‐infrared photons of ∼ 5%. Evidence for partial waveguiding in the cell and for phase‐coherent amplification are presented.