Optical coupler and photonic device

The embodiment of the utility model relates to an optical coupler and a photonic device. According to some embodiments of the utility model, the optical coupler comprises a plurality of waveguide core layers which are formed by waveguide core materials with a first refractive index, the waveguide core layers (i) are arranged in a mutual overlapping relation and (ii) are separated from each other, and (iii) extending longitudinally through the optical coupler from an optical receiving end of the optical coupler towards an optical output end of the optical coupler; and a cladding formed of a cladding material having a second refractive index, the second refractive index being less than the first refractive index, the cladding material surrounding each of the plurality of waveguide core layers. Suitably, light propagating within an outer waveguide core layer of the plurality of waveguide core layers is directed toward an inner waveguide core layer of the plurality of waveguide core layers via evanescent coupling