Asymmetric light propagation in photonic devices

Altering light propagation direction, i.e., forward vs. backward in photonic devices gives rise to same optical response due to reciprocity theorem. Complete or partial manipulation of bidirectional propagation characteristic of light via certain approach may contribute the implementation of functional photonic devices. Complete control over the light propagation direction gives rise to a photonic device that acts as an optical diode whose semiconductor electronic counterpart produces extremely well signal isolation for the backward propagating electrical current. Optical diode also known as optical isolator is sensitive to light propagation direction. The widespread approaches utilize either magneto-optical effect or nonlinear optics concept. Meanwhile, any practical and partial solution considering linear optic approach may be preferable due to compatibility with the integrated photonics. We have proposed various artificially engineered (spatially asymmetric) dielectric media to induce asymmetric optical signal propagation. Numerical results based on finite-difference time-domain results prove that the asymmetric light propagation is achieved with the proposed photonic structures.