Description
Abstract
Undesired backscattering induced by spatial disorder, such as fabrication imperfections and material-composition fluctuations, is a central limitation in reciprocal optical waveguides, which serve as fundamental building blocks of a broad range of classical and quantum photonic systems. Suppressing spatial-disorder-induced backscattering in waveguides has therefore been a longstanding goal in photonics. In recent decades, topological photonic waveguides have emerged as a leading paradigm for robust light transport and were widely regarded as a potential general solution to this problem by offering topologically protected propagation against arbitrary disorder [1]. However, many topological photonic platforms have subsequently been shown to remain vulnerable to backscattering induced by realistic structural disorder [2].
In this presentation, we prove that universal disorder-immune light transport is fundamentally impossible in reciprocal waveguides, irrespective of whether the waveguide is topologically trivial or nontrivial. Building on this proof, we discuss several waveguide systems, in which we propose design principles that can suppress reflection from several common types of disorder, even when the detailed shape and position of the perturbation remain partially arbitrary. We demonstrate this principle by designing reciprocal waveguides in which backscattering from the targeted class of spatial disorder is strongly suppressed, as verified by full-wave simulations.
Taken together, these results clarify the physical origin of the vulnerability of topological protection and the fundamental limitations of robust light transport in reciprocal waveguides. Within these reciprocity-imposed constraints, we introduce a set of waveguide design principles for selectively suppressing backscattering from spatial disorder with partial arbitrariness.
Acknowledgements
The authors acknowledge the funding support from AFOSR-AOARD under grant number FA2386-23-1-4051 (A.S.).
References
[1] Ozawa et al., Rev. Mod. Phys. 91, 015006 (2019).
[2] Rosiek et al., Nat. Photonics 17, 386–392 (2023).
| I am the presenting author | Yes |
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