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Inhomogeneous Polarization Transformation Reveals PT-Transition in non-Hermitian Optical Beam Shift
Version 2 2024-01-31, 17:00
Version 1 2023-10-25, 16:00
preprintposted on 2024-01-31, 17:00 authored by Niladri Modak, Swain Ashutosh, Shyamal Guchhait, Sayan Ghosh, Ritwik Dhara, Jeeban Kumar Nayak, Sourin Das, Nirmalya Ghosh
Despite its non-Hermitian nature, the transverse optical beam shift exhibits both real eigenvalues and non-orthogonal eigenstates. To explore this unexpected similarity to typical PT (parity-time)-symmetric systems, we first categorize the entire parametric regime of optical beam shifts into Hermitian, PT-unbroken, and PT-broken phases. Besides experimentally unveiling the PT-broken regime, crucially, we illustrate that the observed PT-transition is rooted in the momentum-domain inhomogeneous polarization transformation of the beam. The correspondence with a typical non-Hermitian photonic system is further established. Our work not only resolves a longstanding fundamental issue in the field of optical beam shift but also puts forward the notion of novel non-Hermitian spin-orbit photonics: a new direction to study non-Hermitian physics through the optical beam shifts.