A high-performance Echelle grating de-multiplexer based on two stigmatic points and its flat-top solution

A wavelength filter is a key component for numerous photonic integrated circuit applications in optical communication. Researchers put forward several methods to design wavelength filters for which the Echelle grating de-multiplexers (EGDMUXs) are popular and have been extensively studied. In comparison with the traditional EG-DMUXs based on the Rowland mounting, EG-DMUXs based on the two stigmatic points (TSP) method were reported rather late. This paper will present the basic design theory and a high-performance device fabricated on a 250 nm silicon-on-insulator (SOI) platform for validation. The simulation and measurement results of this 1×7 EG-DMUX with 800 GHz channel spacing will be presented and compared. Although the fabricated device has the merits of compact on-chip footprint, low insertion loss and low crosstalk, its narrow 1-dB bandwidth may limit its application in practice. We present our solution to widen the transmission spectrum based on the TSP EG-DMUXs and multimode interferometers.