Rare earth ion impurity centers in crystals and glasses are used as active laser materials, luminescent materials for detection of X-rays and other types of ionizing radiation, in fibre amplifiers and for numerous other applications. This presentation will show how the speed of light in crystals doped with rare earth ions can be slowed down by >5 orders of magnitude and how this potentially could be used in applications ranging from e.g. better optical clocks and frequency standards to improved diagnostics of stroke and heart attack.


The talk will in some detail explain the phenomenon of slow light, show how to create semi-permanent structures in these crystals such that the speed of light is reduced and what this can be used for, including describing applications for laser frequency stabilization and measurement of tissue oxygenation in the body.