Laser Cooling of a Yb Doped Silica Fiber by 18 Kelvin From Room Temperature

Abstract

A ytterbium doped silica optical fiber has been cooled by 18.4 K below ambient temperature by pumping with 20 W of 1035 nm light in vacuum. In air, cooling by 3.6 K below ambient was observed with the same 20 W pump. The temperatures were measured with a thermal imaging camera and differential luminescence thermometry. The cooling efficiency is calculated to be 1.2 ± 0.1%. The core of the fiber was codoped with Al 3+ for an Al to Yb ratio of 6:1, to allow for a larger Yb concentration and enhanced laser cooling.