Handedness-selective chiral transport is an intriguing phenomenon that not only holds significant importance for fundamental research, but it also carries application prospects in fields such as optical communications and sensing, including quantum computing, asymmetric optical switches, polarization controllers, optical isolators, and more. However, previously reported chiral transport devices are static, with each output port locked to a specific mode regardless of the input, which limits functional reconfiguration and transmission capacity improvement.
In a new paper published in Light: Science & Application , a team of scientists, led by Professor Lin Chen and his team from Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, have proposed using the incident polarization diversity to control the Hamiltonian evolution path, achieving polarization-dependent chiral transport. This work combines the concepts of Multiple-Input Multiple-Output and polarization diversity with chiral transport, and challenges the prevailing notion that the modal outputs are fixed to specific modes in chiral transport, thereby opening pathways for the development of on-chip reconfigurable and high-capacity handedness-selective devices.
This work implements anti-directional evolution paths for TE and TM polarizations by introducing L-shaped waveguide cross-sections in double-coupled waveguides. In the L-shaped waveguide, TE and TM polarizations are distributed differently, with TE polarization mainly distributed in the central region and TM polarization primarily in the right region. Although their effective refractive indices increase when either the top or bottom width increases, their sensitivity to top and bottom widths differs. Therefore, by changing the top and bottom widths, the effective refractive indices of TE and TM polarizations change in opposite directions. If an L-shaped waveguide and a rectangular waveguide are combined to form double-coupled waveguides, optimizing the geometry can cause the detuning of TE and TM polarizations to change in opposite directions (Figure 1). The dynamic Hamiltonian trajectories for TE and TM polarizations are different in the Riemann surfaces (Figure 2). Simulated and experimental results demonstrate that different polarizations yield controllable modal outputs (Figure 3).
Light Science & Applications
Polarization-Controlled Chiral Transport