Abstract

The 3d³ ion, Cr³⁺ is the optical centre in several tunable solid state lasers which operate at room temperature¹⁾. The energies of the electronic levels involved in the optical properties of Cr³⁺ ion vary from crystal to crystal²⁾. We deal with gadolinium scandium gallium garnet (GSGG) and gadolinium scandium aluminum garnet (GSAG). The shapes of the low temperature emission spectra from Cr³⁺ ions in GSGG and GSAG are rather different. Figure 1 shows the luminescence spectrum of Cr³⁺ in GSGG. The spectrum is a mixture of the ²E_g → ^A2_g transition, R-line and sharply-structured sideband and the broad band ⁴T_2g → ⁴A_2g emission. The zero-phonon lines at 696.1 nm and 694.9 nm denoted by A and B in Fig. 1b) are due to Cr³⁺ centres in slight different local environments which affect the electronic level of Cr³⁺. The periodic structure is assigned to one- and two-phonon sidebands denoted by A₁, A₂ (B₁, B₂). The separation between lines A and A₁ and between lines A₁ and A₂ is 178 cm⁻¹. As the temperature increases, the new lines denoted by C and D appear at shorter wavelength as shown in Fig. 1b).

© 1988 Optical Society of America