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Anomalous Goos-Hänchen shift and group delay around scattering singularities in complex crystals.
Optics Express
|May 4, 2026
Summary
Scattering singularities are achieved in parity-time (PT) symmetric complex crystals, showing unique optical wave behavior. This research explores anomalous negative Goos-Hänchen shifts and group delays, offering insights into non-Hermitian systems.
Area of Science:
- Non-Hermitian photonics
- Complex crystal optics
- Topological phase transitions
Background:
- Parity-time (PT) symmetry offers unique properties in optical systems.
- Scattering singularities are critical points in wave scattering phenomena.
- Understanding non-Hermitian effects is key to novel optical device development.
Purpose of the Study:
- To demonstrate scattering singularities in PT-symmetric complex crystals.
- To investigate the topological properties of these singularities.
- To analyze anomalous spatiotemporal effects like negative Goos-Hänchen shifts and group delays.
Main Methods:
- Theoretical analysis of optical wave propagation in PT-symmetric complex crystals.
- Characterization of singularities in the 2D parameter space (incident angle θ and angular frequency ω).
- Investigation of phase gradients and their relation to Goos-Hänchen shift (Δ) and group delay (τg).
Main Results:
- Scattering singularities observed as isolated reflection and transmission peaks.
- Phase vortices with topological charge ±1 are formed around singularities.
- Anomalous negative Goos-Hänchen shifts (Δ) and group delays (τg) are found near singularities.
- Negative Δ and τg are correlated with vortex topological charge and linked to backward-amplified pulse propagation.
Conclusions:
- PT-symmetric complex crystals can host scattering singularities even with unbroken PT symmetry.
- The observed negative spatiotemporal effects are linked to topological properties and equivalent gain media.
- Singularities originate from boundary effects and are engineerable by altering non-Hermitian element geometry.
- This work provides a framework for studying novel spatiotemporal effects in non-Hermitian optical systems.
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