Solid-State CW Deep UV Laser Source for Planetary Science Instruments

Both the 2012 Planetary Science Decadal Survey and the 2019 National Academies Astrobiology Strategy prioritize the search for evidence of life, especially extant life, within the solar system and in understanding processes that influence planetary habitability. To support these science objectives, emphasis has been placed on optical based instrumentation for in situ detection and measurement of planetary samples. Vibrational spectroscopy instruments, such as Raman instruments, have been specifically identified for a number of planetary missions including the Mars 2020 and ExoMars 2018 rovers, as well as, instruments for future missions to explore Europa, Mars, and lunar surfaces, because they simultaneously identify biological materials, if present, and the matrix in which they occur, without damaging the sample. Vibrational spectroscopy instruments require a constant wave (CW) or quasi CW (QCW) laser excitation source in the deep ultraviolet (DUV), defined here as 220 nm to 266 nm, for optimal performance. For Raman instruments, DUV laser sources significantly increase the Raman signal return while simultaneously reducing background fluorescence associated with organic compounds. Unfortunately, CW laser sources, particularly solid-state sources, are limited in the commercial domain and virtually non-existent for space-based applications. The SHERLOC instrument developed for Mars 2020 uses a QCW NeCu metal vapor laser at 248.6 nm with a 2 GHz linewidth, 100 mW peak and 1 mW average power, is insufficient for many applications. Commercially available DUV solid-state lasers have been developed; however, these CW solid-state DUV lasers suffer from a well-known loss of power over time due to degradation of the non-linear crystal in the harmonic generator. To address this, commercially developed solid-state DUV lasers use complex mechanical and electronic control mechanisms to continuously move the non-linear crystal to limit degradation while sacrificing cavity and pointing stability, making fiber coupling more difficult. A distinct lack of CW laser sources in the DUV limits the development of a wide array of planetary science instrumentation, and limits highly-capable Raman spectrograph systems for in situ missions. We propose to develop a robust, high-stability CW DUV laser source capable of attaining low power and fluence levels needed to avoid alteration of samples by photodestruction. The laser source will be designed to be coupled into an optical fiber with stable output between 5 mW to 500 mW, a linewidth of less than 1 MHz, and a 100:1 linear polarization ratio for selectable DUV output between 220 nm and 266 nm. DUV laser output is obtained from the second harmonic of the fundamental wavelength, 440 nm to 532 nm, generated from a solid-state laser diode or diode pumped laser source. The fundamental laser sources will be modular so that the laser wavelength can be optimized for specific mission objectives. The second harmonic generator is based on a commercial bow-tie harmonic resonator designed and marketed by our partner institution, Toptica-USA. Current research indicates degradation of the non-linear crystal is likely caused by a two photon process in the DUV, leading to color centers which strongly absorb at the fundamental wavelength and degrade the output power. We propose optimizing the beam waist and non-linear crystal temperature within the existing resonance cavity optical design to eliminate the crystal degradation and the need to move the crystal, thereby improving the cavity and pointing stability. We will leverage our experience in developing space based UV spectrograph (UVS) instruments on LRO, Juno, JUICE, and Europa Clipper to develop a CW DUV laser source with minimal size, weight, and power requirements for use in planetary science instruments. This work is directly relevant to the PICASSO program as the entry TRL of 3 will be increased to TRL 4 upon completion of our breadboard prototype.

Developing Instrument technology to improve measurements for future planetary science missions

This is early/mid-stage (TRL 3) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.