Angular insensitive nonreciprocal ultrawide band absorption in plasma-embedded photonic crystals designed with improved particle swarm optimization algorithm

Abstract

Using improved particle swarm optimization algorithm(IPSO) to drive transfer matrix method(TMM), a nonreciprocal absorber with an ultrawide absorption bandwidth and angular insensitivity(UBAI) is realized in the plasma-embedded photonic crystals(PPCs) arranged by the structure composed of periodic sequence and the quasi-periodic sequence on a normalized scale. Effective dielectric function, which determines absorption of plasma, is subject to basic parameters of plasma, making absorption of proposed absorber easily be modulated by basic parameters of plasma. Compared with different quasi-periodic sequences, Octonacci sequence fully wins both in relative bandwidth and absolute bandwidth. Under further optimization using IPSO, fourteen parameters set to be optimized, absorption characteristics of proposed structure in different amounts of layers of smallest structure unit N are shown and discussed. IPSO is also used to address angular insensitive nonreciprocal ultrawide bandwidth absorption, and optimized result shows excellent unidirectional absorbability and angular insensitivity of proposed structure. The impacts of sequence number of quasi-periodic sequence M, collision frequency of plasma1 ν 1 to absorption in angle domain and frequency domain are investigated. Additionally, the impedance match theory and the interference field theory are introduced to express what the algorithm works out.