Laser cooling of solids containing local centers with electric dipole allowed transitions: a feasibility study

• Materials containing local centers with electric dipole allowed transitions were excited in “laser cooling regime”.
• Fluorescence spectra with a dominant phonon-induced anti-Stokes component were observed.
• Crystals with color centers and Eu2+ ions and dye-doped polymers are potential laser cooling media.

Various insulating materials containing local centers with electric dipole allowed transitions were studied under excitation in the long-wavelength tail of the absorption spectrum (“laser cooling regime”). Though no actual cooling was detected, spectra with a strong anti-Stokes component were observed which demonstrate the possibility to employ electron–phonon bands of electric dipole allowed transitions for optical refrigeration. The mechanisms responsible for the absence of observable optical refrigeration are discussed.