Loss-induced transparency and ITO-based modulator for photonic integrated circuit

Exceptional points (EPs) in non-Hermitian photonic systems offer unique chances for improved sensitivity and nonlinear modulation. While researchers have studied EP phenomena in resonators and microcavities, using them in scalable modulators has faced challenges due to strict gain-loss requirements and fabrication tolerances. In this work, we propose and analyze an EP-assisted photonic modulator that uses a PT-symmetric silicon directional coupler with indium tin oxide (ITO) as a tunable loss medium. By applying an electrical bias to the ITO layer, we can dynamically adjust the gain-loss contrast between the coupled waveguides. This drives the system through the EP and results in sharp nonlinear transmission modulation. This approach combines a compact design, fabrication compatible with CMOS technology, and ultralow control voltage, creating a practical path toward energy-efficient EP-based photonic devices for communication and sensing.