Detection of mode conversion in a subwavelength thin film heterostructure

Abstract

An asymmetric propagation in a photonic diode-like heterostructure is studied theoretically. The heterostructure is composed by two distinct planar waveguides with low and high refractive indices, respectively. The physical mechanism exploited to obtain an asymmetric propagation is based on the matching of eigenmodes. Considering the Transversal Magnetic ( TM ) polarization, it is found that at a specific frequency on the low index waveguide only the first even mode ( TM e 1 ) exists while for the high index waveguide two modes are allowed, the TM e 1 and the first odd mode ( TM o 1 ). We report an asymmetric transmission through the junction of waveguides. On the one hand, it is observed that the TM e 1 mode is able to propagate from the low into the high index waveguide and vice-versa. On the other hand, the TM o 1 mode cannot pass from the high into the low index waveguide.