Proton radiation hardness of periodically poled Rb: KTiOPO4 for high-energy OPA at 2 µm

Development of relevant technologies, for space-borne active instruments for measuring concentration distribution of greenhouse gases (GHG) in atmosphere, is increasingly important with the view of future missions supporting Earth observation programs, by all major space agencies [1] . Wavelength-agile differential absorption LIDARs employing tens of mJ pulse energies in the 2 µm spectral region have the capability of measuring concentrations of main GHG (CO 2 , CH 4 , H 2 O, HDO, N 2 O) throughout atmospheric column owing to well suited absorption lines. The required energy, efficiency and tunability of the LIDAR emitter can be readily obtained by employing high-energy optical parametric amplifier (OPA) based on large-aperture periodically poled Rb:KTP (PPKTP) [2] , seeded by the Nested Cavity Optical Parametric Oscillator (NesCOPO) [3] . Due to radiation environment in low-Earth orbit (LEO) the components, including nonlinear crystals need to be sufficiently radiation-resistant to sustain mission with typical duration of 5 years. We have recently verified that gamma radiation has minimal impact on PPKTP [4] .