Increasing the free spectral range of Fabry-Perot cavities using dissimilar 1D photonic crystals

We present a method for increasing the free spectral range (FSR) of a Fabry-Perot (F-P) cavity without shifting the position of cavity mode using two dissimilar one dimensional photonic crystals (PCs) as mirrors. The resonant cavity is formed between two PCs with photonic band gap (PBG) in slightly overlapping wavelength regions and the resultant PBG, which determines the FSR, is independent of the cavity width but solely determined by the percentage of overlap between the two PBGs. We noticed that the maximum FSR with nearly flat reflection could be achieved for an overlap of less than 13%. The coupling of Eigen modes at the overlapping band edge transmissions of the two PBGs leads to the observed widening of FSR. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

This method proposes increasing the free spectral range (FSR) of a Fabry-Perot cavity by using two dissimilar one-dimensional photonic crystals (PCs) as mirrors without shifting the position of the cavity mode. The resonant cavity is formed between two PCs with slightly overlapping wavelength regions of photonic band gaps (PBGs), and the FSR is determined by the percentage of overlap between the two PBGs. The observed widening of FSR is attributed to the coupling of Eigen modes at the overlapping band edge transmissions of the two PBGs.