Non-Hermitian Low-Power On-Chip Thermal Modulators Operating Off Exceptional Points

As a ubiquitous and economical integrated photonics element, thermal microring resonator (TMRR) modulators play a pivotal role in on-chip communication, computing, and storage. To improve modulation efficiency and reduce power consumption, conventional approaches rely on increasing thermo-optic frequency shifts, which are inherently constrained by material selections and structural designs. Recent advances in non-Hermitian photonics have demonstrated that mode splitting can be boosted at or near the exceptional points (EPs). However, in purely passive structures, the enhanced response is often overwhelmed by the bandwidth broadening and becomes unresolvable. Here, by restricting the heating zone of TMRRs to the nanoscale to magnify the backscattering-induced frequency splitting, we find that the modulation efficiency improves significantly. Furthermore, by introducing another defect-type scatterer to create additional non-Hermiticity, while operating off the EPs, we theoretically and numerically verify an entirely well-resolved 64.2% enhancement in total frequency shift efficiency. Our method synergizes Hermitian and non-Hermitian designs, enriching the functionality of non-Hermitian devices and offering a viable pathway toward high-efficiency, energy-saving integrated optics.