Transparent ceramics are polycrystalline materials that scatter very little light while offering flexibility in shape and volume that are difficult to match with single crystals. In this work, we show that these materials also fulfil important parameters for applications in quantum information and spectral filtering. In particular, we observe homogenous linewidths below 10 kHz at 3.5 K, a value comparable to those found ion most in single crystals.
N. Kunkel, A. Ferrier, C. W. Thiel, M. O. Ramírez, L. E. Bausá, R. L. Cone, A. Ikesue, and P. Goldner, "Rare-earth doped transparent ceramics for spectral filtering and quantum information processing," APL Mater. 3, 096103–7 (2015).