Amplitude-flattened frequency combs in the moving photonic crystals

In this paper, we explore the spectral properties of the moving hollow-core photonic crystal waveguides (PCWs). We find that frequency combs could be generated in the hollow cores of the moving PCWs. Besides, amplitudes of the sidebands in the generated frequency combs are strongly dependent on the spatial field distribution of the core-guided modes of stationary PCWs. Particularly, we find that introduction of the periodic point defects to the innermost rows of the PCW hollow core would significantly modify the spatial field distributions of the guided modes, leading to appearance of the tightly localized defect modes. This, in turn, leads to the enhancement and equalization of the amplitudes of the side bands in the frequency combs generated by the moving PCWs.