Abstract
<jats:p>We present a compact and robust silicon photonic 3 dB adiabatic coupler designed using a deterministic two-step methodology based on shortcuts to adiabaticity. By applying the fast quasi-adiabatic dynamics (FAQUAD) protocol, we homogenize the adiabaticity parameter to significantly compress the device footprint. To eliminate the residual non-adiabatic transitions inherent in the shortened coupler, we apply counter-diabatic (CD) driving via a continuous geometric axis bending profile. This analytical bending correction effectively nullifies crosstalk without requiring iterative numerical optimization. We experimentally demonstrate the CD-driven device on a standard silicon-on-insulator platform, achieving a flat power splitting ratio of approximately 0.5 across a 140 nm bandwidth (1480-1620 nm). These results establish a rigorous analytical framework for designing broadband and fabrication-tolerant integrated photonic components.</jats:p>