ABSTRACT
Several methods have been suggested to improve the efficiency of crystalline lasers based on insulating compounds doped with Ln3+ ions. Among them, the sensitization method is of practical interest. Along with the main generating Ln3+ activator ions, ions of another type are also introduced into a crystal, the so-called sensitizers (S), or donors. Their function is to absorb excitation energy and transfer it to the main ions, the acceptors (A). This process can be represented by () S exc + A → S + A exc , https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781003067962/89564b42-6271-4d92-8163-f65b09ca917b/content/eq609.tif"/> where the subscript “exc” represents an excited state of a given ion. Thanks to the additional absorption bands of the sensitizing ions, the effective pumping band will be extended in the case of broadband optical excitation, e.g., for Xe-flashlamp pumping. Hence, the excitation threshold will decrease, while the emitting intensity increases (sometimes rather strongly). This method has been used for the first time for laser crystals in Reference 1 to improve SE energetic parameters of generating Ho3+ and Tm3+ activators in tetragonal CaMoO4 crystals. In both cases, Er3+ ions were used as sensitizers.
