Diode-pumped Q-switched Alexandrite laser in single longitudinal mode operation with Watt-level output power.

We present significantly improved performance data of a diode-pumped Q-switched Alexandrite laser in single longitudinal mode operation developed as a beam source for resonance lidar systems. The average output power of the laser-operating at the potassium resonance at 770 nm with a linewidth below 10 MHz-could be increased by a factor of five to the Watt-level by means of an optimized resonator design and pump scheme. The pulse energy is 1.7 mJ with a beam quality of M2≤1.1 in both spatial directions at a repetition rate of 500 Hz.

Observations of Reduced Turbulence and Wave Activity in the Arctic Middle Atmosphere Following the January 2015 Sudden Stratospheric Warming.

Measurements of turbulence and waves were made as part of the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX) on the night of 25-26 January 2015 at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W). Rocket-borne ionization gauge measurements revealed turbulence in the 70- to 88-km altitude region with energy dissipation rates between 0.1 and 24 mW/kg with an average value of 2.6 mW/kg. The eddy diffusion coefficient varied between 0.3 and 134 m2/s with an average value of 10 m2/s. Turbulence was detected around mesospheric inversion layers (MILs) in both the topside and bottomside of the MILs. These low levels of turbulence were measured after a minor sudden stratospheric warming when the circulation continued to be disturbed by planetary waves and winds remained weak in the stratosphere and mesosphere. Ground-based lidar measurements characterized the ensemble of inertia-gravity waves and monochromatic gravity waves. The ensemble of inertia-gravity waves had a specific potential energy of 0.8 J/kg over the 40- to 50-km altitude region, one of the lowest values recorded at Chatanika. The turbulence measurements coincided with the overturning of a 2.5-hr monochromatic gravity wave in a depth of 3 km at 85 km. The energy dissipation rates were estimated to be 3 mW/kg for the ensemble of waves and 18 mW/kg for the monochromatic wave. The MTeX observations reveal low levels of turbulence associated with low levels of gravity wave activity. In the light of other Arctic observations and model studies, these observations suggest that there may be reduced turbulence during disturbed winters.