Solar background rejection by a pressure-broadened atomic resonance filter operating at a Fraunhofer wavelength.

We have calculated the solar background rejection of the Mg atomic resonance filter operating at the b(1) Fraunhofer wavelength (518.4 nm) as a function of the pressure-broadened filter linewidth. For pressure broadening induced by the noble gases the solar background rejection decreases from 93% at a 0.002-nm bandwidth to 82-84% at a 0.02-nm bandwidth. Solar background rejection was insensitive to buffer gas and was optimum for the noble gas with the smallest shift-to-broadening ratio.

Experimental demonstration of internal wavelength conversion in the magnesium atomic filter.

We describe what is to our knowledge the first experimental demonstration of internal wavelength conversion in the metastable Mg atomic filter. The filter operates at a Fraunhofer line, thereby offering intrinsic solar background rejection. Incoming green Fraunhofer photons (518 nm) are absorbed by metastable Mg atoms in an oven cell and are converted into UV (384-nm) photons. We observed a green-to-UV conversion efficiency of greater than 50%.