Dual-polarization ultra-wideband nanophotonic beamsplitter

Abstract

High-performance optical beam splitters are of fundamental importance for the development of advanced silicon photonics integrated circuits. However, the performance of state-of-the-art silicon nanophotonic splitters is limited in terms of bandwidth and polarization dependence. Here, we present a new beam splitter approach that exploits modal engineering in slotted waveguides to overcome these limitations, enabling ultra-broadband polarization-insensitive optical power splitting. The proposed splitter relies on a single-mode slot waveguide that is gradually transformed into two strip waveguides by a symmetric taper, yielding equal power splitting. Based on this concept, we experimentally demonstrate insertion loss and power imbalance lower than 1 dB for both, transverse-electric (TE) and transverse-magnetic (TM) polarizations in an unprecedented bandwidth of 390 nm (1260 - 1650 nm).