NASA Innovative Advanced Concepts (NIAC) had their 2016 symposium on August 23-25, 2016
From 21 minutes of this video up to 50 minutes
At 45 minutes, some questions discussing the dopler shifting of the wavelengths.
Absorptivity issues are not as much an issue for dielectrics and are already at 99.999% reflexivity.
Coatings are broadband.