Comparison of the absorption spectra of ruby in the ground state and the excited metastable state

Absorption and emission spectra of ruby in excited states

Infrared Absorption Spectra from Excited States in Ruby

Absorption spectra from excited states of ruby with a high chromium content

Changes in the Absorption Spectra of Ruby at High Excitation Levels

Cw excited state absorption in ruby

Effects of Excited-state Absorption on a Ruby Light Amplifier