Investigator: Madison Hetlage
Atomic and molecular filters are a proven tool in laser based diagnostics. Their use as notch filters has greatly expanded the usefulness of scattering phenomena in both ground testing and remote sensing applications. By tuning a laser to the resonance frequency of a strong transition, intense Mie scattering signals from particles and dust as well as diffuse scattering from windows and walls can be suppressed by several orders of magnitude [1]. The transmitted signal can then be used to measure a variety of parameters. However, current filtering technology limits researchers to the use of the frequency

Atomic Vapor Notch Filter Capabilities, taken from [1]
The transition of interest for this absorption occurs between the excited, metastable 3D2 state in barium vapor and the 3F02 state at 28179.367 1/cm, which corresponds to a wavelength of approximately 354.8 nm. The figure to the right introduces a simplified scheme for generating this absorption feature (which is shown by the purple arrow on the right) by optically pumping barium. In this scheme, a low power continuous wave laser is used to induce the spin forbidden transition at 791.3 nm demonstrated by the red arrow. Population in the excited state decays through collisional quenching and spontaneous emission to the 3DJ metastable manifold, where energy pooling is observed due to the forbidden transition back to the ground state [2]. This pumping scheme, along with pumping at 553.7

Simplified Barium Optical Pumping Diagram, taken from [2]

Preliminary barium vapor cell design