Observation of Electrically Tunable Chirality Inversion in a Slow-Light Waveguide
We identify chiral inversion points in slow-light, glide-plane-symmetric, photonic-crystal waveguides, defined as fixed locations where the local optical chirality changes sign over a narrow wavelength range. We experimentally access this behaviour using a waveguide-embedded InAs/InGaAs quantum dot. The slow-light spectral region is determined from time-integrated and time-resolved photoluminescence, and the dot exciton is electrically tuned across the slow-light bandwidth via the quantum-confined Stark effect. As the emission wavelength is swept through the slow-light region, the directional emission contrast shows a strong wavelength dependence and a sign reversal, consistent with the identified chiral inversion point. Numerical simulations attribute the switching primarily to the pronounced spectral variation of the local optical chirality for emitters displaced from the waveguide center. These results demonstrate on-demand electrical switching of chiral light-matter coupling in nanophotonic waveguides and enable tunable chiral interfaces for integrated quantum photonic devices.