Slow-light-induced Doppler shift in photonic-crystal waveguides

Abstract

In this Rapid Communication, we theoretically discuss a large Doppler shift in a signal slow-light pulse in a photonic-crystal waveguide by considering its reflection at a quasilight speed mirror. The mirror is formed by the photonic band-gap shift induced by the high nonlinearity of a control slow-light pulse, which could be possible in a realistic device. In the simulation, the Doppler shift appears at multiple frequencies due to the Bloch nature of the photonic lattice. Larger but inefficient Doppler shifts occur through nonadiabatic processes, whereas the smallest but more efficient shift (i.e., the intraband Doppler shift) occurs through an adiabatic process. The occurrence of the intraband shift depends on whether the adiabatic process produces a complete reflection of the incident pulse, despite the fact that the pulse penetrates the mirror. A large band-gap shift and a moderately slow mirror satisfy this condition; otherwise, the shift ends at the halfway point.