A Single Reconfigurable Asymmetric Bragg Grating Unit for Scalable Programmable Networks

Programmable Bragg gratings are pivotal for integrated photonics, yet realizing architectures that are simultaneously reconfigurable, scalable, and fabrication‐friendly remains a challenge. Here, we propose a reconfigurable asymmetric Bragg grating (R‐ASBG) that requires only a single grating to achieve multi‐dimensional tunability, including central wavelength, reflection routing, and transmission splitting, without introducing extra optical loss during modulating, thereby maximizing source utilization. Critically, the device inherently suppresses back‐reflection, enabling circulator‐free on‐chip isolation, while its structure has the potential to relax fabrication tolerance compared to conventional dual‐grating schemes. The symmetric dual‐port design ensures straightforward cascadability and scalability in a programmable grating array network (PGAN). Using a Bayesian‐optimized PGAN, we experimentally demonstrate real‐time reconfiguration of diverse spectral responses, including uniform, phase‐shifted, and chirped gratings, as well as coarse wavelength division multiplexing (CWDM). This work establishes a versatile and low‐complexity building block for large‐scale programmable photonic systems, advancing the practical integration of grating devices into next‐generation photonic integrated circuits.