Introduction: The research team led by Nan Chi and Junwen Zhang of Fudan University conducted in-depth research on the challenges faced by traditional access networks due to increased bandwidth demand. They proposed a next-generation flexible coherent optical access solution, taking into full consideration the requirements of low cost, wide coverage, and high flexibility, thereby powerfully promoting the development of next-generation coherent optical access exceeding 100G.

The research group led by Fang Qing at Kunming University of Science and Technology has proposed and studied a highly low-crosstalk arrayed waveguide grating structure on a Silicon-On-Insulator (SOI) platform. In this arrayed waveguide grating, independent micro-ring resonators are integrated on each output channel. By applying a bias voltage to the individual thermo-optic electrodes of each micro-ring, the control of micro-ring resonance peak shift is achieved, ensuring wavelength matching with the focused output of the arrayed waveguide grating. This accomplishes dual filtering of the target wavelength and significantly reduces crosstalk between adjacent output channels of the arrayed waveguide grating. The integration of these low-crosstalk micro-rings offers a new solution for wavelength-division multiplexing in on-chip optical communication.

Lithium niobate materials have attracted extensive attention because of their wide transparent window, high second-order nonlinear coefficient and linear electro-optical coefficient, and stable chemical properties. Lithium niobate crystal has excellent thermoelectric effect, piezoelectric effect, inverse piezoelectric effect and photorefractive effect, and has become one of the preferred materials for advanced photonic components.

The photonic topological insulator, which is the electromagnetic analogy of the topological insulator in electronic systems, has attracted a great deal of attention due to its topologically protected one-way transport of edge states. In the quantum Hall effect system in which the time-reversal symmetry is broken through external magnetic fields, the topological chiral edge states and topological one-way waveguides have the best robustness due to their unique features of free backscattering and immunity against sharp bends and defects. However, the high-efficiency coupling and conversion between topological chiral edge states and classical guided waves, which are essential for feeding energies into and extracting signals from these topological waveguides, have not been well studied.