Polarization-dependent loss compensation on silicon-wire waveguide tap by complex refractive index of metals.

A photodetector can be applied onto a silicon-wire waveguide tap to monitor light signals on waveguides. To meet the complexity of optical integrated circuits, the proposed photodetector would be positioned onto a wafer base instead of being employed and terminated at the edge end of an optical component. Because the silicon-wire-based optical directional coupler shows an undesirably high level of polarization-dependent loss on the tap port compared with the primary port, the complex refractive index of the reflective metal layer was proposed integrated into the direction-changing tap region, made using a 54.7 degrees angle from anisotropic silicon wet etching. This structure compensates for the polarization dependent loss of the tapping signal power for the primary port monitoring.