Narrow bandpass filter with ultra-wide stopband in a hybrid metal-optical Tamm state structure

Narrow bandpass filters (NBPF) play an important role in quantum communications, optical biometrics and other fields. However, traditional narrow bandpass filters have limited stopband capabilities. Here, an ultrawide stopband narrow bandpass filter is realized by combining a metal layer with a distributed Bragg reflector (DBR) structure to simultaneously excite the upper and lower Tamm plasma polarization (TP) modes. Numerical simulations show that the transmittance of the filter exceeds 94 % at a wavelength of 1.55 mu m with a full width at half maximum (FWHM) of 8 nm. In addition, the addition of metal layer Ge reduces the electric field intensity of the lower DBR structure, effectively reducing the side peak, making the filter stopband range reach 1 mu m-20 mu m, which is 32 times that of traditional NBPF. Our research results provide a method to obtain narrow-band optical signals from ultra-broad and strong background noise, which facilitates the field of quantum communication.