Electromagnetically induced transparency in a mono-isotopic ¹⁶⁷Er:⁷LiYF<inf>4</inf>crystal below 1 Kelvin: Microwave photonics approach

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement. Electromagnetically induced transparency allows for the controllable change of absorption properties, which can be exploited in a number of applications including optical quantum memory. In this paper, we present a study of the electromagnetically induced transparency in a 167Er:7LiYF4 crystal at low magnetic fields and ultra-low temperatures. The experimental measurement scheme employs an optical vector network analysis that provides high precision measurement of amplitude, phase and group delay and paves the way towards full on-chip integration of optical quantum memory setups. We found that sub-Kelvin temperatures are the necessary requirement for observing electromagnetically induced transparency in this crystal at low fields. A good agreement between theory and experiment is achieved by taking into account the phonon bottleneck effect