Optical design and characterization of the MOMA laser head flight model for the ExoMars 2020 mission

A space-qualified flight model of a pulsed ultraviolet (UV) laser has been developed for the Mars Organic Molecule Analyzer (MOMA) instrument of the ExoMars 2020 mission. The design is based on a passively Q-switched Nd:Cr:YAG laser oscillator with subsequent two-stage frequency quadrupling. It emits nanosecond pulses with an energy tuneable between 13 µJ and 130 µJ at a wavelength of 266 nm. Considering its small physical dimensions and weight, the interior of the laser head is rather complex. Besides the aforementioned infrared oscillator and frequency conversion stage it contains the pump optics, two wavelength division assemblies within main beam path, a complex monitoring stage including two photodiodes for pulse energy measurement, a beam shaping setup and a deflection unit for fine adjustment of the beam pointing towards the sample location within the instrument. Most of the laser head is enclosed in a hermetically sealed housing, while the deflection unit is sealed separately. Both volumes are filled with 1 bar of dry, filtered air.