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Seminarium ISQI - dr. Arnab Laha

Application-Specific Photonic Systems Hosting Exceptional Points

Speaker: Dr. Arnab Laha
Date, Time: 01.06, 15:00 - 16:00

Link to MS Teams meeting

The synergy of non-Hermitian physics and photonics has revealed a novel and promising direction for building a wide range of photonic components. The appearance of Exceptional Point (EP) singularities is one of the fascinating features of non-Hermitian or open systems, which has lately been implemented in a wide range of photonic systems with gain/loss to achieve various interesting quantum-optical applications associated with light-matter interactions. The encounter of an EP in the parameter space of a non-Hermitian system can be defined with a simultaneous coalescence of corresponding coupled eigenvalues and the associated eigenvectors, which results in arising of a topological defect in the system’s eigenspace. In this context, a PT-symmetric system, a class of non-Hermitian systems with real eigenvalues, encounters an EP while experiencing a spontaneous phase transition from an exact-PT-phase to a broken-PT-phase. Hosting of such EP singularities, which were once considered as purely mathematical objects, has shown an immense potential to be an unconventional light manipulation tool leading to asymmetric-state-transfer, antilasing, slow light control, unidirectional light propagation with enhanced nonreciprocity, ultrasensitive sensing, and so on.

Here, we reveal the hosting of second-order EPs (EPs) in gain-loss assisted guided wave geometries, like optical waveguides and fibers. Adiabatic and nonadiabatic light propagation characteristics induced by dynamically encircled EP2s are investigated in the context of a chirality-drove asymmetric mode conversion scheme. Here, irrespective of the inputs, the device delivers two different particular dominating modes while propagating in opposite directions. Moreover, in the presence of nonlinearity, an all-optical nonreciprocal EP-based light dynamics is explored, leading to a novel mode-selective isolation scheme. Here, depending on the nonlinearity-level, the device allows the nonreciprocal transmission of two different dominating modes while operating (separately) in two different directions. The findings would enrich the versatile platform for building all-optical integrated (on-chip) photonic components.