6 μm pulsed OP-GaAs OPO laser for unambiguous water ice detection on the Moon and other planetary bodies

摘要

NASA demands the special laser transmitter for the lidar system to detect water-ice on the Moon and other planetary bodies. Based on the data from the Moon Mineralogy Mapper (M~3) instrument, the water ice was on the Moon has been claimed, but such a claim was disputed because OH- and/or H_2O-bearing materials share the absorption line at the wavelength range of 2.8-3 μm. Lunar Flashlight, another mission to explore the surface of Moon (the launch date delays to this year), allows scientists map the minerals on dark side of the Moon, but it still has difficult to resolve the ambiguity mentioned above. The absorption line around 6.08 μm uniquely associated with the bending resonance of H_2O has not any comparable vibration in confounding OH-bearing materials. However, a 6.08 μm laser in the gap between the atmospheric windows, middle-wave infrared (3-5 μm) and long-wave infrared (8-12 μm), has not been commercially available. Our approach is a Q-switched Ho:YLF laser pumped the orientation-pattern Gallium Arsenide optical parametric oscillator (OP-GaAs OPO) for generating high-energy laser pulses at the wavelength of 6.08 μm. In the current design, a 1.94 μm Tm:fiber is used as the pump source of Ho:YLF laser. In the compact design, a 1.94 μm laser diode will replace the Tm:fiber laser as the pump source. The combination of proposed 6.08 μm laser and the latest HgCdTe avalanche photodiode (APD) array allow us to design a lidar capable of unambiguously identifying water ice on the Moon and Mars from their respective orbits, enabling novel science and in-situ resource utilization. Our instrument is an enabling technology for the Artemis program and future missions.