Controlling light transport in non-Hermitian waveguide arrays

Area of Science:

• Photonics
• Condensed Matter Physics
• Waveguide Optics

Background:

• Controlling light propagation in scattering media is a significant challenge.
• Non-Hermitian waveguide arrays offer potential for light manipulation.
• The roles of the non-Hermitian skin effect and topology in transmission stability are not fully understood.

Purpose of the Study:

• To analytically investigate the influence of the non-Hermitian skin effect and topology on light propagation.
• To derive exact and asymptotic solutions for light excitation in waveguide arrays.
• To identify robust mechanisms for controlling light transport in photonic systems.

Main Methods:

• Analytical investigation using an extended Hatano-Nelson model with open boundaries.
• Derivation of exact solutions for eigen-site and single-site excitations (n=1).
• Derivation of asymptotic solutions for n ≥ 1 excitations.

Main Results:

• The skin effect leads to edge-localized propagation with energy-dependent gain/attenuation for eigen-site excitation.
• Topological light funneling is observed in single-site excitation.
• A unique 2n-directional Gaussian transport is discovered for n ≥ 1 single-site excitation, extendable via superposition.

Conclusions:

• Three robust control mechanisms are identified: gain/loss-modulated propagation, non-reciprocal funneling, and multi-directional spreading.
• These findings provide design principles for topological photonic devices.
• Potential applications include scattering-resistant lasers and invisibility materials.