Modeling Transient Loss Due to Ionizing Particles in Silicon Photonic Waveguides

A general, computationally efficient, physics-based model for the continuous time-domain description of transient loss in silicon (Si) photonic waveguides due to impinging ionizing particles is presented. The model combines Beer–Lambert and Drude formalisms with the ambipolar transport equation (ATE) and applies a number of carefully vetted simplifying assumptions to obtain a highly compact form. The model is validated using nanosecond pulses of tightly focused 639-nm laser light to induce localized high-level generation events and mimic heavy-ion strikes within Si photonic waveguides of varying geometry. Electron–hole pairs (ehps) generated in these events cause free-carrier absorption (FCA) of a continuous 1535-nm probe signal in the waveguide, which is observed as a transient drop in detected photocurrent on a high-speed oscilloscope. Measured transients show excellent agreement with model predictions.