Efficiency improvement in Thulium-doped fibers via excited state pumping

In this contribution we propose a new way to simultaneously increase (almost double) the amplification efficiency and reduce the thermal issues of Thulium-doped fibers. This technique is based on pumping the excited state of the Thulium fiber, in order to bring the ions from the pump level to the upper laser level via stimulated emission instead of via phononic relaxation processes. Our simulations show that using this technique the efficiency of the amplification process can be increased by almost a factor of 2.