Improving performance in ytterbium-erbium doped waveguide amplifiers through scattering by large silicon nanostructures

Abstract

Optical waveguide amplifiers have seen a growing interest in the last years due to their applications in telecommunication. This paper reports a notable increase of the relative gain of Yb3+/Er3+ codoped Bi2O3–GeO2 waveguides by introducing disorder in the form of silicon nanostructure as scattering centers. A photoluminescence enhancement of about 10 times for the 520 nm and 1530 nm emission bands is observed in the waveguides when the silicon nanostructures are introduced. Increase of the Yb3+/Er3+ effective absorption, due to the scattering provided by the silicon nanostructures, and decrease of [Bi+], caused by the introduction of silicon, are proposed as likely causes for the luminescence and gain enhancement. The pedestal waveguides were fabricated by RF-sputtering followed by optical lithography and reactive ion etching. RF-sputtering of silicon together with Yb/Er and Bi2O3–GeO2 glass, followed by heat treatment, produced Yb3+/Er3+ codoped Bi2O3–GeO2 waveguides with silicon nanostructures of size 25–30 nm. The resulting relative gain reached 5.5 dB/cm at 1542 nm representing an enhancement of 50% with respect to waveguides without silicon nanostructures. This strategy of introducing appropriate disorder may open an avenue for designing and manufacture of novel photonic devices in this emerging field of integrated optics.