These characteristics combine in one single material the benefits of glasses and of some single crystals. They enable to obtain or to amplify short pulses and / or to have a large tunability in wavelength like in glassy materials, with very good yields, and high damage thresholds, comparable to those of crystals. Finally, a very important point for a large-scale development, it has been widely demonstrated for the purpose of UV photolithography that it is possible to produce non-doped crystals of great size and excellent quality. With an adaptation of growing conditions, it is quite possible to manufacture crystals doped with 20, even 30 cm in diameter for amplifiers of high power laser chains.

In a recent article published in "Laser Physics", the MIL team shows that it is possible to further improve the performance of these crystals by lowering their temperature. It is indeed becoming more common to lower the temperature of laser crystals of high power laser chains (as for example for Ti-sapphire and YAG: Yb lasers). This allows to both strengthen the crystal against the flux damages, by a better evacuation of the heat, and lower the thresholds by increasing the absorption of pump radiation, this also increasing the laser gain. For 3-level systems, like Yb³⁺ doped crystals, higher improvements can be expected in low temperature operation as these systems becomes like a 4-level one, whose performance is much better. It is shown that for CaF₂: Yb³⁺, cooling to the liquid nitrogen temperature allows reducing the threshold of laser operation and increasing its efficiency by more than 15% (as compared to room temperature), and achieving a power yield (luminous power emitted / absorbed light power) of more than 80%.

For these results, the CIMAP-MIL team is sought today by several research groups including the "Laser Particle Acceleration Group" of FZ Dresden-Rossendorf for the study and development of crystals of several centimeters in diameter, by an evolution of the technique developed in Caen. These crystals will first be tested in place of fluorophosphate glasses used in the laser POLARIS. If successful, it is envisaged to develop a petawatt system (10¹⁵ W) based on complete CaF₂: Yb³⁺.