Spatial heterogeneity of the doping mode: A potential optical reconfiguration freedom of photonic doping epsilon-near-zero media

A photonic doping epsilon-near-zero medium (ENZ) is usually regarded as a homogeneous ENZ with a certain effective permeability. However, the spatial heterogeneity of doped ENZ and its potential influence on the external electromagnetic fields have not attracted enough attention. In this work, we discover a potential optical reconfiguration freedom of photonic doping ENZ, the spatial heterogeneity of the doping mode, which is released with the breaking of the magnetic average effect by several air gaps. By numerical investigation, we found that for an epsilon-mu-near-zero medium (EMNZ) constructed by complementarily doped ENZ, the transmittance in response to the variation in the width of the introduced air gap is tuned by the spatial heterogeneity of the doping mode. For a perfect magnetic conductor obtained through doped ENZ, the heterogeneous doping mode acts as a freedom to adjust the reflective phase. Based on these results, we respectively construct an ultrasensitive optical displacement sensing device and an optical single-pole-double-throw switch through doped ENZs. This work reveals an intrinsic difference between photonic doping ENZ and homogeneous magnetic ENZ, which has rarely been discussed in previous works. Meanwhile, the spatial heterogeneity of doped ENZ shows significant application prospects in the field of mechanically regulated optical devices.