Nonlinear germanium nanocluster doped planar waveguides

Abstract

In future all-optical networks pure optical signal processing, such as switching, routing and signal regeneration is going to be essential. Each of these tasks puts different constraints to the chosen solution regarding speed, wavelength range of operation, noise and polarization properties etc. However, a large fraction of these functionalities may be obtained by utilizing optical components with a strong nonlinear refractive index [1]. Silica has a very low nonlinear refractive index. Fortunately, silica also has a very low loss. As a consequence of the latter a significant nonlinear phase shift may be accumulated over a large distance i.e. over tens of kilometers of optical fiber. Because of this long length silica is not a viable material when designing compact nonlinear planare lightwave circuits. Recently, nanostructured materials have been proposed as promising candidates for nonlinear waveguides. More specifically glass based materials doped with nanometer sized clusters of for example metals or semiconductors. In this work we demonstrate processing of waveguides with strong confinement of the electrical field achieved using air trenches and processing of glass doped with germanium nanoclusters. We illustrate how the cluster size may be controlled and we show that realization of nonlinear waveguides may be within reach.