Abstract

Ni²⁺-doped MgF₂ is a well-known tunable laser in the near infrared.¹ The tunability arises from the vibronical broadening of the infrared emission bandof crystals doped with Ni²⁺ in octahedral sites. The vibronically broadened opticals bands of Ni²⁺-doped crystals are described with the configurational coordinate model (Fig. 1). As can be seen from this model, the excited-state absorption (ESA) transition ³T₂(³F) → ³T₁(³F) coincides with the long-wavelength edge of the infrared emission band ³T₂(³F) →³A₂(³F). ESA is an important loss mechanism for the infrared laser emission, because it originates from the same energy level. Also, it reduces the tuning range at long wavelengths.² All known Ni²⁺ lasers require cooling. The aim of this work is to investigate whether this can be explained with the temperature dependence of the bandwidths: at low temperatures the optical bands are narrower, thus improving the conditions for laser operation, because the overlap of the emission band with the ESA band and also with the ³A₂(³F)→³T₂(³F) ground state absorption band (GSA) is reduced.

© 1994 IEEE