Resolving Light Handedness with an on-Chip Silicon Microdisk

The efficient manipulation of circularly polarized light with the proper handedness is key in many photonic applications. Chiral structures are capable of distinguishing photon handedness, but while photons with the right polarization are captured, those of opposite handedness are rejected. In this work, we demonstrate a planar photonic nanostructure with no chirality consisting of a silicon microdisk coupled to two waveguides. The device distinguishes the handedness of an incoming circularly polarized light beam by driving photons with opposite spins toward different waveguides. Experimental results are in close agreement with numerical results, which predict extinction ratios over 18 dB in a 20 nm bandwidth. Owing to reciprocity, the device can also emit right or left circular polarization depending on the chosen feeding waveguide. Although implemented here on a CMOS-compatible platform working at telecom wavelengths, the fundamental approach is general and can be extended to any frequency regime and technological platform.