Multimode Calculations of a Metal Clad Waveguide

Accurate mode analysis is essential for designing high-performance metal-clad waveguides used in sub-wavelength disc lasers. Understanding the distribution and characteristics of guided, leaky, and radiation modes enables engineers to optimize gain utilization, minimize optical losses, and improve overall laser efficiency. However, structures supporting large numbers of modes can make identifying the most relevant solutions a significant design challenge.

This application note demonstrates how FemSIM's full-vector Finite Element Mode Solver is used to analyze the modes of a metal-clad circular waveguide employed in a sub-wavelength metal-clad disc laser. The solver simultaneously computes guided, leaky, and radiation modes, providing a comprehensive picture of waveguide behavior. To efficiently isolate the modes of interest, the workflow calculates a large set of modes and automatically ranks them according to optical loss. Because guided modes typically exhibit the lowest losses, they can be readily identified without the need for extensive manual post-processing.

The application note also highlights FemSIM's ability to output only a selected subset of calculated modes, allowing engineers to focus on the guided solutions while avoiding unnecessary storage of high-loss leaky and radiation modes. This streamlines both data management and subsequent design analysis.

By combining full-vector electromagnetic simulation with efficient mode filtering and post-processing capabilities, FemSIM enables faster and more effective waveguide design. Engineers can confidently evaluate modal characteristics, optimize the use of gain materials, and accelerate the development of advanced semiconductor laser and integrated photonic devices while reducing design iterations and computational overhead.