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.
Low-threshold terahertz molecular laser optically pumped by a quantum cascade laser
We demonstrate a low-threshold, compact, room temperature, and continuous-wave terahertz molecular laser optically pumped by a mid-infrared quantum cascade laser. These characteristics are obtained, thanks to large dipole transitions of the active medium: NH3 (ammonia) in gas state. The low-power (<60 mW) laser pumping excites the molecules, thanks to intense mid-infrared transitions around 10.3 μm. The molecules de-excite by stimulated emission on pure inversion “umbrella-mode” quantum transitions allowed by the tunnel effect. The tunability of the quantum cascade laser gives access to several pure inversion transitions with different rotation states: we demonstrate the continuous-wave generation of ten laser lines around 1 THz. At 1.07 THz, we measure a power of 34 μW with a very low-threshold of 2 mW and a high differential efficiency of 0.82 mW/W. The spectrum was measured showing that the linewidth is lower than 1 MHz. To our knowledge, this is the first THz molecular laser pumped by a solid-state so...
Actuating Principle of Online Automatic Balancer with Counter Weight Driven by Magnetic Force
Kinematic precept of mass block in automatic balancer is proposed following the principle of online automatic dynamic balancing.By combination of electromagnet and permanent magnet,the magnetic circuit of the balancer with ring coil and rare earth permanent magnet is designed.Actuating process of the balancer is discussed and then a step drive voltage waveform is defined.For the high-speed grinding motorized spindle 170MD12Y16,the mechanical structure and dimensions of the balancer are schemed out.The electromagnetic simulations for the designed balancer are conducted and the better coil ampere-turns and reluctance adjusting ring thickness are then determined.The validity of simulation results is verified by a balancer driving experiment and the desired voltage value and its duration time are also determined.the designed balancer has a stable operation process without out-of-step and fluctuation around balanced position when the ampere-turns are considered as 1 kA,the reluctance adjusting ring thickness 0.2 mm,the driving voltage 12.4 V and the voltage duration time 120 ms.