Controllable Excited State Atomic Barium Filter for Remote Sensing and Ground Testing

This work aims to develop an atomic vapor notch filter functioning at the third harmonic of the high-power and robust Nd:YAG laser (355 nm). Vapor filters are a critical component of several laser diagnostic techniques due to their deep, narrow, and tunable light absorption capabilities. Most notably, these filters have enabled measurements of temperature, flow velocity, aerosol properties, and electron temperature and number density through applications spanning space technology, including remote sensing, electric propulsion, re-entry, hypersonics, and combustion.

However, current filtering technology is limited to wavelengths which are either unsafe for the human eye, lack the scattering signal strength necessary for longer range measurements, or are challenging to generate. The proposed project looks to overcome these limitations and improve our diagnostic capabilities by developing a barium vapor filter functioning at an easily accessible wavelength outside the retinal transmission region. This filter would benefit from increased signal strength and eye safety, decreased sunlight background, negligible ozone absorption, rapid tunability, and easy integration into any third harmonic equipped Nd:YAG system. While this technology could augment several established diagnostic techniques for propulsion and hypersonics ground testing, these parameters are particularly advantageous for laser remote sensing—namely lidar (light detection and ranging) systems, which use scattering signals to measure atmospheric parameters. Lidar improvement has been named a priority under NASA TABS element 8.1.5. If successful, this project would enable higher precision and safer atmospheric profiling on our own planet and other celestial bodies.

While currently at a low TRL, previous studies provide confidence in this new and innovative approach. Still, filter development and implementation present engineering and scientific challenges. These will be addressed through 1) fabrication and testing of a dense barium vapor source, 2) an in-depth experimental and modeling study of barium kinetics using absorption measurements, and 3) ground-based and airborne atmospheric lidar measurements. The interactions with NASA lidar expertise and facilities provided by this fellowship would greatly extend the impact of this filter technology for space applications.

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.

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