Ultracompact and broadband wavelength (de)multiplexer based on asymmetrical directional coupler with subwavelength grating

We demonstrate an ultracompact $(\sim 9 \mu \mathrm{m})$ wavelength demultiplexer based on SWG-assisted asymmetrical directional coupler. Low loss $(\gt 0.2 dB)$ and high extinction ratio ($\gt 19$ dB) are obtained for almost the whole O-band and C-band.