Mode transmission analysis method for photonic lantern based on FEM and local coupled mode theory

Area of Science:

• Photonics and optical engineering
• Computational electromagnetics
• Waveguide theory

Background:

• Photonic lanterns (PLs) are crucial for mode manipulation in optical systems.
• Accurate simulation of mode transmission in PLs is essential for device design and optimization.
• Existing numerical methods often face challenges with computational complexity and precision.

Purpose of the Study:

• To introduce a novel, full vector numerical simulation method for analyzing photonic lantern mode transmission characteristics.
• To develop a method capable of handling arbitrary input mode fields with high precision and reduced computational load.
• To demonstrate the method's effectiveness and utility for optimizing photonic lantern designs.

Main Methods:

• The proposed method integrates the finite element method (FEM) with local coupled mode theory (LCMT).
• It employs a full vector approach for comprehensive analysis of mode transmission.
• The method's validity is confirmed using a three-core photonic lantern as a test case.

Main Results:

• The novel FEM-LCMT method significantly reduces computational complexity compared to traditional approaches.
• High precision in analyzing mode transmission characteristics is achieved.
• Optimization based on the method's insights improved mode selectivity for LP01 and LP11 modes to 44.5 dB and 54.7 dB, respectively.
• Over 95% coupling efficiency was maintained during optimization.

Conclusions:

• The developed FEM-LCMT simulation method offers a powerful and efficient tool for photonic lantern analysis.
• The method provides valuable insights for the optimization design of photonic lanterns.
• Significant improvements in mode selectivity and coupling efficiency are achievable through guided geometric parameter optimization.