A Novel Planar Waveguide Super-Multiple-Channel Optical Power Splitter

In this paper, we have proposed a novel planar waveguide optical-power-splitter design with a large number of splitting channels. The design uses the wavefront lateral interference in light propagation in a slab waveguide, with its core properly adjusted in different areas for achieving different effective indices for the required phase delays. Therefore, the whole structure is equivalent to a nonblocking all-pass filter, hence, suffers a very small insertion loss. Another unique advantage of this structure lies in its weak length dependence on the number of splitting channels; although its lateral size has to be scaled up as the channel number increases, as opposed to conventional splitters with both of its length and lateral size scaled up with increasing channel numbers. Our numerical simulation results show that, for a 1-to-256 channel splitter within a working wavelength band from 1530 to 1570 nm, the insertion loss is below 1.3 dB. The channel nonuniformity is less than 5 dB within the same band. The required size is within 2.5 mm by 10 mm on the silicon-on-insulator platform. The proposed structure can readily be extended to other material platforms, such as the silica-based planar lightwave circuit or semiconductors. Its fabrication process is fully compatible with standard clean-room technologies, such as photolithography and etching, without any complicated and/or costly approach involved.