Design of a thermally tunable optical filter based on one-dimensional ternary photonic band gap material

Designof a tunable band pass filter using one dimensional ternary periodic refractive index profile has been presented. Design of the proposed filter is based on the model of Kronig–Penny in solid state physics. In this present filter, the desired wavelength regions can be tuned by altering the temperature or the incidence angle. A Ge/Si/air multilayer system is considered here. The refractive indices of Si and Ge layers have been taken to be functions of temperature as well as wavelength. Due to the dependence of refractive indices of Si and Ge on temperature, transmission characteristic of the structure changed, and this property has been exploited to shift the transmission band. Hence, the proposed ternary structure can be utilised to tune the pass bands by changing the temperature or the incident angle. Detailed analysis shows that ternary structure gives better performance than the binary structure in terms of tunability.