Low-loss single-mode operation in silicon multi-mode arrayed waveguide grating with a double-etched inverse taper structure

We investigate the single-mode operation in a silicon arrayed multi-mode waveguide grating. By introducing a double-etched structure at the boundary of a star coupler with inverse-tapered waveguides (WGs), the suppression of the mode-coupling between adjacent arrayed multi-mode WGs, and the adiabatic optical mode conversion between a FPR (free propagation region) and arrayed WGs can be achieved with a reduced phase error of the arrayed WGs. The fabricated four-channel Si arrayed waveguide grating (AWG) demonstrates a good performance level, such as a low insertion loss of 0.61 dB (0.73 dB) and low adjacent crosstalk less than −31.3 dB (−32.2 dB) for transverse-electric (TE) (transverse-magnetic, TM) polarization, in the range of ∼1300 nm wavelength.