Unconventional optical response of time-domain Fibonacci quasicrystals

We investigate the propagation and localization of light waves in the time-domain Fibonacci quasicrystals (FQCs), which are constructed following the Fibonacci sequence generation rule. We demonstrate the transmission of amplified optical waves through FQCs. The reflectivity of FQCs displays unusual behavior since the reflection band may repeatedly flip and amplify for the alternating sequences. Thus, amplified light wave transport can result in both outputs of FQCs, leading to similar transmission and reflection spectra, although the amplification for the two outputs differs. It is found that the localization of light is only possible if the reflection band does not flip. In addition, spectral modifications resulting from the index modulation of a specific sequence-based FQC may contrast sharply with the spectral response of a conventional FQC. The findings of this computational study aid in enhancing the capabilities of the time-domain FQCs in a range of applications, such as high-transmissivity bidirectional optical frequency shifters, light localization in time, and amplified multifrequency quantum cascade terahertz radiation.