Details

Autor(en) / Beteiligte

• Feofilov, S.P.
• Kulinkin, A.B.
• Konyushkin, V.A.
• Nakladov, A.N.

Titel

The role of two-step excitation processes in laser cooling experiments: CaF2:Eu2

Ist Teil von

• Optical materials, 2016-10, Vol.60, p.240-243

Ort / Verlag

Elsevier B.V

Erscheinungsjahr

2016

Quelle

Elsevier ScienceDirect Journals

Beschreibungen/Notizen

• The fluorescence of CaF2 single-crystals containing Eu2+ ions was studied under the excitation in the long-wavelength tail of the absorption spectrum which is due to electric dipole allowed transitions (“laser cooling regime”). Though no actual cooling was detected, spectra with a dominant anti-Stokes component were observed which demonstrate the possibility to employ electron-phonon bands of Eu2+ f-d transitions for optical refrigeration. The absence of observable optical refrigeration is ascribed to Eu2+ two-step photoionization processes that are responsible for the excited state absorption. The role of two-step excitation of impurity centers (excited state absorption) in laser cooling experiments is discussed. •CaF2:Eu2+ crystals were excited in the long-wavelength tail of the electron-phonon absorption band (“laser cooling regime”).•Fluorescence spectra with a dominant phonon-induced anti-Stokes component were observed.•The role of two-step excitation of impurity centers (excited state absorption) in laser cooling experiments is discussed.