Theoretical verification of a silicon-wire flat-spectral-band wavelength filter based on multimode interference couplers with symmetric and asymmetric splitting ratios for the broadband operating range

A novel, to the best of our knowledge, device scheme for a silicon-nanowire flat-spectral-band wavelength optical filter is proposed and theoretically demonstrated. The proposed wavelength filter is composed of cascade-connected multiple delayed interference optical delay lines, together with several multimode interference couplers with symmetric and asymmetric splitting ratios. Theoretical calculations based on analytic and numerical simulations exhibit flatband spectra over a wavelength range of >80 nm with potentially better production yield for arbitrary channel spacing. (C) 2021 Optical Society of America