  All optical diodes (AODs) play an important role in quantum optics and
information processing, in which the information is encoded by photons. Only
circularly polarized lights are able to carry the spin states of photons, which
has been intensively used in quantum computing and information processing and
enable new research fields, such as chiral quantum optics. An ideal AOD should
be able to work with arbitrary polarizations states, including circularly
polarized lights, which has not been demonstrated yet. In this paper, we
theoretically demonstrate for the first time a nanophotonic AOD that is able to
work with circularly polarized lights. The AOD nanostructure is based on a
heterostructure of two-dimension silica and silicon photonic crystals (PhCs).
By controlling the effective refractive indices of the PhCs and using an
inclined interface, we are able to exploit generalized total reflection
principle to achieve non-reciprocal transmission of circularly polarized
lights. In addition, the nanophotonic AOD is able to achieve high forward
transmittance greater than 0.6 and high contrast ratio close to 1 in a broad
wavelength range of 1497 nm to 1666 nm. The designed nanophotonic AOD will find
broad applications in optical quantum information processing and computing.
