Broadband and Circulator-Free On-Chip Dispersion Compensation at 2-µm Waveband Using Silicon Nitride Chirped Bragg Gratings

The 2-µm waveband has emerged as a critical spectral window for nonlinear optics, spectroscopic sensing, and optical communications, where precise dispersion engineering is paramount. In this work, we demonstrate a broadband dispersion compensator for the 2-µm waveband using silicon nitride chirped Bragg gratings (CBGs) monolithically integrated with a 2 × 2 multimode interferometer (MMI). This device architecture eliminates the need for external circulators. The CBGs are apodized to suppress group delay ripples and linearly chirped to achieve an 80-nm operational bandwidth. The device delivers a maximum group delay of 58 ps and a tunable dispersion coefficient of 0.84 ps/nm, enabling precise phase matching for nonlinear processes. Fabricated in a CMOS-compatible process, this compact compensator unlocks new opportunities for on-chip mid-infrared photonics, including dispersion-managed frequency combs and broadband supercontinuum generation.