Laser cooling ytterbium doped silica by 67 K from ambient temperature
Brian Topper, Stefan Kühn, Alexander Neumann, Alexander R. Albrecht, Angel Flores, Denny Häßner, Sigrun Hein, Christian Hupel, Johannes Nold, Nicoletta Haarlammert, Thomas Schreiber, Mansoor Sheik‐Bahae, Arash Mafi
Abstract
) silica rod by 67 K from room temperature was achieved. For the pump source, a 100 W level ytterbium fiber amplifier was constructed along with a 1032 nm fiber Bragg grating seed laser. Experiments were done in vacuum and monitored with the non-contact differential luminescence thermometry method. Direct measurements of the absorption spectrum as a function of temperature were made, to avoid any possible ambiguities from site-selectivity and deviations from McCumber theory at low temperature. This allowed direct computation of the cooling efficiency versus temperature at the pump wavelength, permitting an estimated heat lift of 1.42 W/m as the sample cooled from ambient temperature to an absolute temperature of 229 K.