Ultra‐Compact and Ultra‐Broadband Guided‐Mode Exchangers on Silicon

Abstract

Abstract On‐chip mode exchangers play very important roles for multimode photonics, which has drawn much attention for many applications. However, it is still very challenging to achieve compact mode exchangers with high performances in an ultra‐broad bandwidth. Here a universal approach of on‐chip mode manipulations is proposed by manipulating the multimode excitations/interferences, and ultra‐compact mode exchangers are realized with low excess losses (ELs) and high extinction ratios (ERs) using special metamaterial structures. The presented TE i – j mode exchangers enable the exchange between the TE i and TE j modes in an ultra‐broad bandwidth. The designed TE 0–1 and TE 0–2 mode exchangers have footprints of 1.3 × 2.7 µm 2 and 1.9 × 2.9 µm 2 , respectively. Theoretically, they have ELs ≈ 0.2 dB and ERs = 19–32 dB at 1550 nm, while their bandwidths for achieving ER > 10 dB reach 340–400 nm. The fabricated devices have measured ELs of 0.2–0.3 dB and ERs above 12.0–13.2 dB in the setup‐limited wavelength range of 1520–1607 nm. The proposed approach is flexibly extendable to enable on‐chip mode exchanges, which are promising for multimode silicon photonics in many applications.