All fiber approach to solid-state laser cooling

An all fiber approach to optical cooling is being investigated experimentally and theoretically using Tm-doped fiber laser and Tm-doped fiber cooler. A single mode, high efficiency and high power Tm-doped fiber laser is used to pump at the absorption edge of Tm-doped fiber coolers, one made by germanate and the other by tellurite glasses. The glass characterization shows that the quenching effect, which is negative for cooling processes in the fiber, in germanate glass is much stronger than that in tellurite glass. The preliminary results of experiments indicate cooling effects could occur in the fiber, but net cooling in the system has not been achieved. A theoretical framework aimed at understanding the nature of cooling in this laser cooling system has been developed which shows that the temperature in the sample could increase even if the fiber core is indeed cooling. The details of the temperature dynamics depend on many factors such as background loss and absorption of scattered light by the heat spreader.