Modeling quasi-dark states with temporal coupled-mode theory

Area of Science:

• Optics and Photonics
• Electromagnetics
• Resonant Systems

Background:

• Coupled resonators are crucial for tailored spectral responses and novel functionalities.
• Temporal Coupled-Mode Theory (TCMT) is a widely used modeling tool for these systems.
• The lumped-element nature of TCMT can lead to limitations in certain scenarios.

Purpose of the Study:

• To identify and address a key limitation of TCMT in predicting dark states in coupled resonator systems.
• To compare TCMT predictions with experimental data and more comprehensive simulation methods.
• To propose a correction to enhance the accuracy of TCMT.

Main Methods:

• Investigated a coupled system of three microring resonators.
• Compared TCMT predictions with experimental observations.
• Utilized Transfer Matrix Method (TMM) and Finite-Difference Time-Domain (FDTD) simulations for validation.
• Analyzed the excitation/decay mechanisms of supermodes within the TCMT framework.

Main Results:

• TCMT inaccurately predicted the existence of a dark state in the studied microring resonator system.
• Experimental results and TMM/FDTD simulations contradicted the TCMT prediction.
• The limitation was traced to the TCMT's handling of supermode excitation and decay.

Conclusions:

• TCMT has a significant limitation in predicting dark states for coupled resonators.
• A corrected TCMT model reconciles predictions with experimental and advanced simulation results.
• The findings and proposed correction are applicable to various electromagnetic resonant systems.