TWIN WAVEGUIDE BASED DESIGN FOR PHOTONIC INTEGRATED CIRCUITS

摘要

An asymmetric twin waveguide(ATG) structure (11) significantlyreduces the negative effects ofinter-modal interferences in symmetrictwin-waveguide structures and whichcan be effectively used to implementa variety of optical devices. The ATGstructure (11) of the invention can bemonolithically fabricated on a singleepitaxial structure without the necessityof epitaxial re-growth. The effectiveindex of the passive waveguide in theATG is varied from that of a symmetrictwin waveguide such that one mode ofthe even and odd modes of propagationis primarily confined to the passivewaveguide and the other to the activewaveguide (71). The different effectiveindices of the two coupled waveguidesresult in the even and odd modesbecoming highly asymmetric. The modewith the larger confinement factor inthe active waveguide (71) experienceshigher gain and becomes dominant.Furthermore, a grating region isincorporated atop the passive waveguide(125) to select certain frequencies fortransmission of light through the passivewaveguide (125).