High-polarization-degree and high-extinction-ratio tm optical switch based on photonic crystal slabs

A high-polarization-degree and high-extinction-ratio polarization TM optical switch based on photonic crystal slabs comprises an upper photonic crystal slab and a lower photonic crystal slab that are connected to form a unity. The upper photonic crystal slab is a first tetragonal lattice photonic crystal slab with a TE band gap, and the unit cell of the first tetragonal lattice photonic crystal slab consists of a high-refraction-index rotary square rod, one first-slab dielectric rod and a background dielectric. The first-slab dielectric rod consists of a high-refraction-index dielectric tube and a low-refraction-index dielectric therein, or consists of a high-refraction-index slab film, or consists of a low-refraction-index dielectric. The lower photonic crystal slab is a second tetragonal lattice photonic crystal slab with a complete band gap, and the unit cell of the second tetragonal lattice photonic crystal slab consists of a high-refraction-index rotary square rod, one second-slab dielectric rod and a background dielectric. The frequency of the normalized TM optical switch ranges from 0.252 to 0.267.