The Design of an On-Chip Silicon Photonic Diode
This work presents numerical calculation of electromagnetic waves in unidirectional on-chip silicon optical diodes. An original optical diode, designed by Wang et. al. [Opt. Express. 19, 26948-26955 (2011)], is based on breaking of spatial inversion symmetry and the directional band gap difference of two 2D photonic crystals comprising a hetero-junction structure. The dimensions of our structure are however different from those of Wang et. al. The electromagnetic waves in the diode obey the Maxwell’s equations which were solved with appropriate boundary conditions using the finite difference time domain as implemented in the MEEP software. MEEP is an acronym for M.I.T. Electromagnetic Equation Propagation. Our solutions show the existence of a distinct unidirectional isolation effect in the designed hetero-junction slab. The band structures for the lowest frequency mode of the transverse electric fields in the bulk of each of the 2D crystals comprising the hetero-junctions were also determined by solving the wave equation in frequency space. The MPB (M.I.T Photonic Bands) software was used. The band structures reveal directional band gaps which are responsible for the optical isolation property of the composite hetero-junction.