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Q: Fachverband Quantenoptik und Photonik

Q 44: Laser Technology and Applications

Q 44.1: Talk

Thursday, March 5, 2026, 11:00–11:15, P 2

Hybrid FDTD-transfer matrix framework for fast Bragg grating response modeling — •Yasmin Rahimof, Igor A. Nechepurenko, M. R. Mahani, and Andreas Wicht — Ferdinand-Braun-Institut (FBH), Berlin, Germany

Bragg gratings play a central role in integrated photonics because they enable fine control over reflection and transmission spectra. Numerical solvers such as the finite-difference time-domain (FDTD) method can capture their full electromagnetic behavior but quickly become impractical when simulating long or complex structures due to heavy computational demands. To overcome this limitation, we introduce a modeling strategy that derives a transfer matrix method (TMM) from short-segment FDTD simulations and then reuses it to predict the response of extended gratings. By composing transfer matrices obtained from short FDTD simulations, we can rapidly reconstruct spectra for gratings that are orders of magnitude longer than the original simulation domain. This method reproduces both reflection and transmission with errors consistently under 4% compared to full FDTD, while cutting computational time by more than an order of magnitude. Our study demonstrates that the TMM provides a reliable and scalable surrogate model, enabling efficient design exploration for structures ranging from tens to hundreds of grooves. The framework offers a powerful balance between accuracy and speed, making it particularly valuable for the development of large-scale photonic components.

Keywords: surrogate modelling; surface Bragg grating; FDTD simulation; Transfer matrix method; diode lasers