Ultra-compact optical 90 degrees hybrid based on a wedge-shaped 2 x 4 MMI coupler and a 2 x 2 MMI coupler in silicon-on-insulator

We propose an ultra-compact optical 90 degrees hybrid with the smallest length of 10(7) mu m, consisting of a wedge-shaped 2 x 4 MMI coupler connected with a 2 x 2 MMI coupler using silicon nanowaveguide technology. Neither cascaded phase shifters nor waveguide crossings are attached to the proposed 90 degrees hybrid in coherent receiving system. The proposed device is demonstrated on silicon-on-insulator (SOI) with 220nm thick top-silicon layer and 2 mu m thick buried oxide layer. A high performance of the proposed 90 degrees hybrid is exhibited experimentally with a high extinction ratio larger than 20dB, an excess loss mostly less than 0.5dB, a common mode rejection ratio better than -20dB and phase deviation within the range of 5 over C-band spectral range. (C) 2013 Optical Society of Americahttp://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000327494000083&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701OpticsSCI(E)EI8ARTICLE2328423-284312