Symmetry-guided scattering engineering in modular gain-loss photonic crystals

Area of Science:

• Photonics and Optics
• Condensed Matter Physics
• Materials Science

Background:

• Non-Hermitian optics explores systems with gain and loss.
• Photonic crystals offer unique light manipulation capabilities.
• PT symmetry provides a framework for understanding complex optical behaviors.

Purpose of the Study:

• To systematically study the scattering properties of multilayer photonic crystals with gain-loss units.
• To investigate the influence of stacking geometry and defect engineering on non-Hermitian optical responses.
• To establish a unified framework linking spectral singularities to device functionalities.

Main Methods:

• Fabrication and characterization of multilayer photonic crystals.
• Theoretical analysis of scattering matrices and optical responses.
• Numerical simulations of PT-symmetric and PT-broken configurations.

Main Results:

• Simultaneous coherent perfect absorption (CPA) and lasing observed in PT-symmetric configurations.
• Decoupling of CPA and lasing channels upon PT symmetry breaking, while preserving reciprocity.
• Demonstration of symmetry-enabled functionalities: broadband mirrors, high-Q filters, unidirectional transport, and transparent windows.

Conclusions:

• A unified, symmetry-guided framework connects spectral singularities to device functionalities.
• The study provides practical routes for designing and controlling non-Hermitian photonic systems.
• Findings pave the way for next-generation optical devices with tailored properties.