Densely doped active waveguides

Abstract

Dielectric waveguides doped with rare-earth (RE) ions can be used as optically pumped amplifiers and lasers. In long (several meters) fiber devices, an outstanding example being the erbium-doped fiber amplifier, high gain (>30dB) can be accumulated along the device at low concentrations of RE ions. The length of integrated devices-[l] is restricted to a few centimeters and. therefore, two orders of magnitude higher RE concentration is required to provide sufficiently large gain. However, at high dopant levels strong interactions between RE ions tend to severely reduce gain efficiency Especially, cluster formation, which is difficult to eliminate, is harmful, since fast (nanosecond tune scale [2]) energy transfer between clustered ions may totally quench the gam lor realistic pump powers Understanding, and quantitative evaluation, of concentration dependent gain limiting mechanisms is of the fundamental importance for optimizing fabrication and design of densely doped active devices, in this talk progress in the ongoing research addressing this issue (2-8), as well as examples of demonstrated RE-doped integrated devices [9-12] and the design concepts for gain improvement [13-15), will be presented.