Impact of chirping on non-reciprocal temporal evolution of a Gaussian pulse in a one-dimensional Weyl semimetal-based defective photonic crystal

Abstract Weyl semimetals, a class of topological materials exhibits significant optical non-reciprocity without the need for an external magnetic field or high-intensity light sources. Adding Weyl semimetal layers to a one-dimensional photonic crystal as defect layers may improve the structure’s non-reciprocity. This study investigates the influence of chirping on the non-reciprocal temporal evolution of Gaussian pulses in a one-dimensional photonic crystal with double-layer defects composed of silicon dioxide and Weyl semimetal. Using the transfer matrix method and Fourier transform, we analyze the transmission spectrum and pulse dynamics under linear and quadratic chirping conditions. The structure exhibits a photonic band gap with two defect modes whose resonant frequencies shift depending on the incident direction (forward or backward), demonstrating strong optical non-reciprocity. Chirping induces rapid oscillations in the transmitted pulse profile, with quadratic chirping causing more pronounced distortions than linear chirping. While non-chirped pulses retain their shape, chirped pulses undergo compression, decompression, or multi-peak formation, depending on the chirp type and carrier frequency. The temporal evolution of pulses is highly sensitive to the incident direction and carrier frequency, with forward-propagating pulses tuned to defect modes showing compression, whereas backward-propagating pulses exhibit decompression or oscillatory tails. Quadratic chirping introduces stronger modifications to pulse profiles compared to linear chirping, highlighting its potential for advanced pulse shaping in non-reciprocal systems. These findings highlight the critical role of chirping in controlling pulse propagation in defective photonic crystals, offering insights for applications in optical isolation, signal processing, and tunable photonic devices.