Planar concave grating with flattened spectral response for wavelength demultiplexing optical interconnection

A 4-channel planar concave grating device with a flattened spectral response based on SU-8 polymer is presented. The flattened spectral response is accomplished by using an optimized multi-mode interference coupler as the input aperture of the device for spectrally separated channels. The mode field distribution in the input plane is controlled by adjusting the width of input taper coupled to the multi-mode interference coupler. The effects of the input taper width on the flattened spectral response are demonstrated in detail through simulation results. The devices are realized by using an SU-8 polymer strip waveguide with a UV lithography technology. Experimental results show that the flattened spectral response can be easily controlled by adjusting the taper width.