Infiltrating a thin or single-layer opal with an atomic vapour: Sub-Doppler signals and crystal opticsElias Moufarej, Isabelle Maurin, Ilya Zabkov, Athanasios Laliotis, Philippe Ballin, Vasily Klimov and Daniel BlochEPL, 108 1 (2014) 17008DOI: https://doi.org/10.1209/0295-5075/108/17008