Fibertek proposes to develop technology for power scaling a frequency doubled Er:YAG single frequency laser source to meet the needs for a planned water vapor DIAL space-based instrument. Our approach will focus on quantifying the system level benefits of reduced-temperature operation of a power-scaled Er:YAG oscillator and power amplifier. A primary challenge to the Er:YAG laser system is inherently low gain and quasi-three-level lasing transitions of the erbium activator ions. It is well-established that reducing the laser gain medium to sub-ambient temperatures improves achievable laser efficiency. However, models based on cross-section data from the current literature that simply use Boltzman statistics for scaling cannot account for the observed improvements, inhibiting system trades of performance versus temperature. Fibertek proposes to address the lack of data in the current literature by collecting spectroscopic data over the temperature range 77K-300K to determine the optimum gain medium temperature for Er:YAG. This data will be integrated into an advanced energetics model to accurately predict improvements in laser efficiency. The model predictions will be validated through laser demonstrations as well as to guide a study to assess the improvements relative to potential SWaP penalties associated with operating at a reduced temperature. Energy scaling of Er:YAG could potentially provide NASA with a compact laser transmitter that could revolutionize weather and climate research by providing three dimensional distributions of water vapor profiles, estimates of perceptible water vapor, high resolution methane column measurements, distributions of planetary boundary layer heights, and attenuated profiles of aerosols and clouds. Potential NASA Applications (Limit 1500 characters, approximately 150 words): The key NASA application include the following all of which have been identified as mission and technology development area in the 2018 Earth Science Decadal Survey. An Er:YAG MOPA could provide a higher energy, more efficient, more robust and lighter weight approach for Water Vapor and Methane Differential Absorption Lidar systems Coherent detection 3-D wind measurement systems Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words): DoD: Lidar systems and illuminators require high pulse energy for greater range and wider field of view, with a requirement for operation in the eyesafe window (1400-1700nm). Er:YAG at 1645nm is well suited for these applications. Commercial: An Er:YAG laser with higher pulse energy can extend range for current wind lidar systems for wind farm and other types of commercial wind measurements. Duration: 6
