A reconfigurable grating unit based on a Bragg-grating-assisted Mach–Zehnder interferometer

Bragg gratings possess unique functional attributes as fundamental integrated photonic devices. A reconfigurable grating unit based on a Bragg-grating-assisted Mach–Zehnder interferometer (GAMZI) is proposed as a versatile building block for programmable photonics. By integrating identical Bragg gratings into both arms of a thermo-optically tunable MZI, the device enables dynamic spectral reshaping—achieving bandwidth-tunable bandpass filters, phase-shifted gratings, and broadband filters with precise control over extinction ratios and bandwidths. The GAMZI architecture uniquely suppresses back-reflections while maintaining high port scalability, overcoming key limitations of conventional grating designs. Furthermore, a double-triangle recurrent network array using cascaded GAMZI units is demonstrated, enabling advanced functionalities such as ring-grating resonators, sampled gratings, and on-chip coarse wavelength division multiplexing. This work establishes a scalable and reconfigurable platform for on-chip spectral engineering, paving the way for adaptive optical signal processing in next-generation programmable photonic circuits.