We developed a cryogenically cooled Yb:YAG laser as the pump beam for a pulsed Raman laser based on CVD grown
diamond crystals. The Q-switched cryogenic Yb-doped YAG 1030 nm pump laser delivered 340 W at 40 kHz with
diffraction-limited beam quality, with an optical efficiency of 80%. The record average power of 24.5 W was generated
from the Raman laser at 1193 nm. Modeling of the performance confirmed the corresponding Raman gain coefficient,
13.5 cm/GW. The laser was operated at room temperature and under cryogenic cooling at 77 K, with equal performance.
KEYWORDS: Diodes, Semiconductor lasers, Cryogenics, Oscillators, Optical amplifiers, Crystals, Laser crystals, Laser systems engineering, Temperature metrology, High power lasers
We present our recent developments in high-power, high-efficiency cryogenic Yb:YAG laser systems. Specifically, we
will discuss our 2.3-kW master oscillator power amplifier (MOPA) which has shown optical wall-plug efficiencies
above 30-% (diode-driver input to optical output). This laser system has been operated for long run times with
continuous wave and pulsed output formats. The beam quality factor, M2, of the MOPA has been measured to be less
than 2 and it is currently limited by the master oscillator. We are working to improve the device's beam quality and
output power. In addition, we have demonstrated an all-cryogenic Yb:YAG laser that produced 29 W of optical power.
Use of cryogenic diode laser pumps represents our next step towards achieving greater than 50% efficient high-power
laser systems.
We present a holographic Raman lidar system, which can provide temperature profiles of the atmosphere. The Raman lidar has the potential to operate continuously over a 24 hr period, with a predicted accuracy of 1% at altitudes greater than 20 km. The distinguishing feature of our lidar that allows 24 hr measurements is the holographic optical element. The holographic optical element can resolve individual rotational Raman lines at high efficiency. Furthermore, this high resolution substantially increases the signal to noise of the lidar system, thereby allowing daytime measurements with out appreciable increase in error.
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