Anti-Stokes fluorescence of Cr3+ ions doped crystals excited in one-phonon vibronic sidebands

Abstract The fluorescence of Cr3+ ions doped insulating crystals was studied under the laser excitation within the one-phonon vibronic sidebands of zero-phonon 4A2 - 2E transitions. The phonon-assisted anti-Stokes fluorescence spectra were observed at ambient and liquid nitrogen temperature. The spectroscopic results suggest that one-phonon vibronic sidebands of zero-phonon lines in impurity ions fluorescence spectra are of interest from the point of view of achieving optical refrigeration starting at ambient temperature as well as significantly below it.