Pr(3+) upconversion laser performance improvement by use of pump scavenging

Using pump power efficiently in a Pr(3+) -doped fluoride fiber upconversion laser can raise conversion efficiency and lower pump threshold. Pump scavenging reuses the pump power not absorbed in the first pass through a laser cavity. Both theory and experiment show that the backreflected pumps have almost the same effect on the conversion efficiency as the forward ones and that total backreflection of the pumps can lead to a 60% increase in absorbed pump power, a twofold increase in output power, and a 40% reduction of threshold.