Ultra-high extinction ratio optical modulation via interference-engineered mach-zehnder modulator

Achieving an ultra-high dynamic extinction ratio (ER) in optical modulators is crucial for enhancing signal fidelity, dynamic range, and energy efficiency in optical communication systems. However, conventional Mach-Zehnder modulator (MZM) suffers from limited ER due to fabrication-induced imbalances, thermal drift, and imperfect Y-branch splitters, making it difficult to maintain high contrast without complex calibration or temperature control. Here, we propose and experimentally demonstrate a dual-branch ER-Boost MZM that achieves a dynamic ER over 38 dB without requiring perfect 50:50 splitters or bandwidth compromise. The architecture introduces an auxiliary extinction-enhancement branch that actively suppresses residual optical leakage through phase-controlled destructive interference. An adaptive bias controller provides sub-millisecond feedback to stabilize the ER against environmental fluctuations. Experimental results confirm long-term ER stability within a 3 dB drift, while the ER-Boost concept itself can be readily extended to silicon photonic platforms. Ziyuan Shi and colleagues develop an interference-engineered Mach-Zehnder modulator that actively suppresses residual optical leakage using an auxiliary extinction-enhancement branch and adaptive bias control. The device achieves a dynamic extinction ratio above 38 dB and significantly improves the performance of photon-counting optical communication systems.