Optical mode conversion based on silicon-on-insulator material Ψ-junction coupler and multimode interferometer

• Published in: Optics and laser technology 2021-10, Vol.142, p.107177, Article 107177
• Main Authors: Tu, Dao Duy, Tam Linh, Ho Duc, Phuoc, Vuong Quang, Thang, Dao Duy, Dung, Truong Cao, Hung, Nguyen Tan
• Format: Article
• Language: English
• Subjects: Beams (radiation); C band; Converters; Couplers; Crosstalk; Insertion loss; Integrated circuits; Multimode interferometer and [formula omitted]-junction waveguide; Multiplexing; Photonics integrated circuit; Planar lightwave circuits; Propagation modes; Silicon-on-insulator material
• ISSN: 0030-3992; 1879-2545
• DOI: 10.1016/j.optlastec.2021.107177

•Flexible convert between three modes from TEi (i = 0, 1, 2) to TEj (j = 0, 1, 2).•Simple structure by combining two Ψ-junction couplers and multimode interferometers.•High optical mode conversion efficiency. In mode-division multiplexing (MDM) networks, converting modes back and forth between a higher-order mode and a lower-order mode plays a vital role in improving network capacity and flexibility. This paper presents a spatial optical mode conversion supporting three modes based on two Ψ-junction couplers and two multi-mode interference couplers (MMIs). The proposed device can arbitrarily convert a TEi mode to a TEj mode (where i, j = 0, 1, 2) by setting three phase-shifters at 0 or 180 degrees, which are introduced at the Ψ-junction and MMI couplers. Through numerical simulations using the spatial three-dimensions beam propagation method (3D-BPM), the mode converter shows a high conversion efficiency with the insertion loss smaller than 0.2 dB and the crosstalk below −20 dB at the center wavelength of 1.55 μm. The device works effectively in C band, partially in S and L bands within a wideband up to 80 nm. We believe that the proposed device would be a potential platform for applications in MDM networks and photonic integrated circuit systems.