Ultranarrow bandwidth spectral filtering for long-range free-space quantum key distribution at daytime
David Höckel, Lars Koch, Eugen Martin, Oliver J. Benson · Optics Letters · 2009
We describe a Fabry-Perot-based spectral filter for free-space quantum key distribution (QKD). A multipass etalon filter was built, and its performance was studied. The whole filter setup was carefully optimized to add less than 2 dB attenuation to a signal beam but block stray light by 21 dB. Simulations show that such a filter might be sufficient to allow QKD satellite downlinks during daytime with the current technology.