Multimode silicon photonic waveguide corner-bend

An ultra-sharp multimode waveguide bend (MWB) based on a multimode waveguide corner-bend (MWCB) is proposed and realized. With the present MWCB, total internal reflection (TIR) happens and the light propagation direction of all the mode-channels can be modified with low excess losses (ELs) and low inter-mode crosstalk (CT) in the optical communication bands from 1260 nm to 1680 nm. For the MWCB designed for the TE 0 and TE 1 modes, the ELs are less than 0.18 dB and the inter-mode CTs are less than -36 dB in the wavelength range of 1260-1680 nm. The measurement results show the fabricated MWCB works very well as predicted by the theory. It is very flexible to extend the present MWCB for more mode-channels by simply adjusting the core width. For example, the MWCB designed with a 35 µm-wide core has an EL less than 0.54 dB and inter-mode CT less than -24 dB for the ten TE-polarization modes (i.e., TE 0 ∼TE 9 ) in the wavelength-band of 1260-1680 nm. For the present MWCB, the fabrication is also very convenient because no tiny nano-structure and no additional fabrication steps are needed. It also shows that the present MWCB is not sensitive to the sidewall angles even when the angle is up to 8°. The proposed MWCB is promising for multimode silicon photonics because of the simple structure, easy design, easy fabrication as well as excellent performances in an ultra-broad wavelength-band.