Laser cooling of solids under the influence of surface phonon polaritons

Laser cooling of solids with anti-Stokes fluorescence in rare earth-doped low phonon samples, which support surface phonon polaritons (SPhP), placed in the vicinity of the sample supporting SPhP in the same or different wavelength region is considered in this paper. As an example, the laser cooling process in an ytterbium-doped yttrium aluminum garnet (Yb3 + : YAG) sample placed near yttrium aluminum garnet (YAG) as well as silicon carbide (SiC) samples has been investigated. All Yb3 +: YAG, YAG, and SiC samples can support SPhPs in different frequency ranges. It was shown that for short distances between samples, when SPhPs propagating in the sample undergoing laser cooling and SPhPs propagating in the next sample supported at room temperature are coupled, the laser cooling process can deteriorate substantially. In the opposite case, the SPhPs do not influence the cooling process significantly, even if the distance between the samples is less than the dominant wavelength of thermal radiation. The influence of coupled SPhPs on the laser cooling process in the case of samples with different sizes and for different distances between samples was investigated. These results are important for the development of optical solid state cryocoolers. (C) 2017 Optical Society of America