Mode Converter and Multiplexer With a Subwavelength Phase Shifter for Extended Broadband Operation
David González‐Andrade, Raquel Fernández de Cabo, Jaime Vilas, Irene Olivares, A. Días, José Manuel Luque‐González, J. Gonzalo Wangüemert‐Pérez, Alejandro Ortega‐Moñux, Íñigo Molina‐Fernández, Robert Halir, Pavel Cheben, Aitor V. Velasco
Abstract
On-chip mode converters and multiplexers are fundamental components to scale the capacity of silicon optical interconnects by using different spatial modes of waveguides. Recently, we proposed a low loss and compact mode converter and multiplexer consisting of a subwavelength-engineered multimode interference coupler, tapered waveguides as phase shifter and a symmetric Y-junction. However, the narrow spectral response of the tapered phase shifter limited the device crosstalk performance. In this work, we demonstrate that the use of a subwavelength grating phase shifter with low phase-shift errors substantially reduces the crosstalk and expands the operational bandwidth. A complete multiplexer-demultiplexer link consisting of two devices in back-to-back configuration was fabricated in a 220-nm silicon-on-insulator platform. Experimental measurements of the complete link show insertion loss below 2 dB and crosstalk less than −17 dB over a bandwidth of 245 nm (1427 – 1672 nm).