Author(s): Shon Cook, Till Rosenband, and David R. Leibrandt
Crystals doped with rare-earth ions, and cooled to 4 K, can be optically pumped so that they are transparent over narrow frequency ranges. Using these crystals as spectral windows could allow for reliable, long-term laser frequency stabilization.
[Phys. Rev. Lett. 114, 253902] Published Tue Jun 23, 2015