Ultra-compact reconfigurable device for mode conversion and dual-mode DPSK demodulation via inverse design

Abstract

The mode multiplexing/de-multiplexing devices are key components for mode-division multiplexing (MDM) technology. Here, we propose an ultra-compact and reconfigurable mode-conversion device via inverse design, which can selectively implement multichannel mode conversion controlled by input phase shifts (Δ φ ). The device can transform input TE 0 (TE 1 ) mode to TE 4 (TE 3 ) mode at Δ φ =0, or from TE 0 (TE 1 ) to TE 1 (TE 2 ) at Δ φ =π spanning the wavelength range of 1525–1565 nm. We further demonstrate an integrated monolithic module based on the mode conversions to directly demodulate the dual-mode difference phase shift keying (DPSK) signal which significantly reduces the device size and benefits for future dense integrations in MDM systems.