Narrowband channel drop filter with high transmission based on nested hexagonal cavity

Optical photonic crystal channel drop filters (CDFs) are widely used due to the sensitivity of individual wavelength among the group of channels in optical communication networks. However, most of the existing filtering scheme still suffer from low transmission efficiency. Here, we propose an eight-channel CDFs with narrow bandwidth and high transmission based on a dual positive hexagonal nested array which is sandwiched between two parallel line defect waveguides. The circular dielectric rods with different radius are arranged in the ring resonant cavity to diminish light leakage and, therefore, increase drop efficiency and quality factor Q. The results show that the drop efficiency and Q factor of the nested cavity CDF can achieve 99% and 5033, and the average values of the cascaded eight-channel CDFs are found up to 92.73%, 3217, respectively, and the channel crosstalk is between − 61.92 and − 14.90 dB. The proposed CDFs offer highly selective spectrum filtering capabilities, showing great potential in high-precision optical sensing and optical communication.