Densely packed waveguide array (DPWA) on a silicon chip for mode division multiplexing.

A densely packed waveguide array (DPWA) structure for mode division multiplexing on a silicon chip is proposed. The DPWA consists of several narrow waveguides with different widths, which are densely packed with gaps of 100nm. The lateral dimension of the DPWA is comparable to the conventional multimode waveguide used for mode division multiplexing on silicon. An efficient and parallel (de)multiplexing structure is proposed. For a three-mode DPWA with a 15μm-long (de)multiplexing structure, insertion losses of -0.05dB and cross-talks of -20dB are achievable for all the modes in a wide wavelength range. The present DPWA favors a compact direct bending. In a 45μm-radius 90° bend, insertion losses of -0.1dB and cross-talks of -20dB are obtained. The proposed DPWA structure also shows a large fabrication tolerance.