Optical seminar | 24 August 2022

Exceptional singularity or Exceptional point (EP) is a critical point in system parameter space for which the nature of a mathematical model governing a physical system is fundamentally different compared with neighboring points. An EP of order can be defined as a particular branch point singularity in the system’s parameter space, where the number of eigenvalues and the corresponding eigenstates simultaneously coalesce, and hence the effective Hamiltonian of the underlying system becomes defective. We have investigated various gain loss-assisted multimode supported planar optical waveguides (and optical fibers) to host different order EPs.
Here, non-Hermiticity has been introduced in terms of a multilayer gain-loss profile based on only two control parameters. We have proposed the unconventional propagation characteristics of the coupled modes following dynamical parametric encirclement processes, enclosing the identified EPs. Our proposed schemes open up a potential platform to develop optical mode converters for integrated or on-chip photonic circuits.

Main paper/arXiv, related to the seminar, and other references

1. Sibnath Dey et.al., “Nonlinearity Induced Anomalous Mode Collapsing and Non-chiral
Asymmetric Mode Switching around multiple Exceptional Points” published in Physical Review B (APS). DOI:
10.1103/PhysRevB.101.125432.
2. Sibnath Dey, et.al., “Nonadiabatic Modal Dynamics Around a Third-order Exceptional Point in a
planar waveguide” published in Optics Communication, DOI: 10.1016/j.optcom.2020.126644.
3. Sibnath Dey, et.al., “Exotic light dynamics around fourth order exceptional point” published in
JOSA b (OSA), DOI: 10.1364/JOSAB.416232.
4. Arpan Roy, Sibnath Dey, et.al., "Exceptional-point-induced asymmetric mode
conversion in a dual-core optical fiber segment, published in Optics Letter (OSA) DOI: 10.1364/OL.458549.
5. H. K. Gandhi, A. Laha, S. Dey, et.al., “Chirality Breakdown in the Presence of Multiple
Exceptional Points and Specific Mode Excitation” published in Optics Letter (OSA). DOI: Opt. Lett.45, 1439(2020).