Thermally tunable terahertz omnidirectional photonic bandgap and defect mode in 1D photonic crystals containing moderately doped semiconductor

A new one-dimensional photonic crystal (1DPC) containing moderately doped silicon (m-Si) semiconductor is proposed and its tunable properties are theoretically investigated. The tunable complex permittivity of m-Si with temperature is the central idea that makes the 1DPC thermally tunable. The 1DPC systems such as (m-Si/SiO2)(12) and defective (m-Si/SiO2)D-6(m-Si/SiO2)(6) are examined in the spectral range of 0.4-0.8 THz with varying temperature from 40 to 100 K. Air and m-Si are considered as defect layer (D) in two different 1DPC systems. Our simulation shows that the photonic band gap (PBG) shifts to higher frequency and the omnidirectional PBG gets narrower with increasing temperature. The defect mode in both defective 1DPCs shifts to higher frequency with increasing temperature. The temperature sensitivity of peak transmission is found better in the air defective 1DPC, while that of defect frequency is better in the m-Si defective 1DPC. The angle of incidence and polarization dependency of the defect modes are studied in detail. The present work can be utilized for the development of tunable omnidirectional mirrors and narrow bandpass filters in the terahertz region as well as THz light based thermal sensors.