Designs and Optical Tests of Thermal Links for an Optical Refrigerator

Dielectric mirror leakage at large angles of incidence limits the effectiveness of solid state optical refrigerators due to reheating caused by photon absorption in an attached load. In this paper, we present several thermally conductive link solutions to greatly reduce the net photon absorption. The Los Alamos Solid State Optical Refrigerator(LASSOR) has demonstrated cooling of a Yb+ doped ZBLANP glass to 208 K. We have designed optically isolating thermal link geometries capable of extending cooling to a typical heat load with minimalabsorptivereheating, and we have tested the optical performance ofthese designs. A surrogate source operatingat 625 nm was used to mimicthe angular distribution of light from the LASSOR cooling element. While total link performance is dependent on additional factors, we have found that the best thermal link reduced the net transmission of photons to 0.04%, which includes the trapping mirrors 8.1% transmission. Our measurements of the optical performance of the various link geometries are supported by computer simulations of the designs using Code V, a commercially availableoptical modelingsoftwarepackage.