arXiv subjects

Rajarshi Sen

Publications and source records attributed to Rajarshi Sen.

3 recordsLinked to original sources

arXiv2025

Photonic-Spin governed absorption in a mu-near-zero subwavelength gyromagnetic cylinder

Realizing non-reciprocal scattering and absorption from subwavelength elements has several applications across the electromagnetic frequency spectrum. Here we show that gyromagnetic cylindrical rods with subwavelength dimensions exhibit strong absorption with diminished scattering in a narrow frequency band for an incident plane wave. We show that the strong narrowband absorption depends on the photonic-spin of the incident wave. Further, it is shown that this spin-dependent absorption leads to non-reciprocal reflection and absorption characteristics of an array of gyromagnetic cylinders suspended over a reflecting plane. The theoretical claims of strong spin-dependent absorption in subwavelength elements is validated by experimentally demonstrating nonreciprocal absorption and transmission from a single gyromagnetic rod placed in a substrate integrated waveguide.

physics.optics↗

arXiv2023

Poynting Vector Spin in Gyromagnetic Medium and its Impact on Backward Power Flow in Waveguiding Structures

This paper investigates the reactive power and spin of instantaneous Poynting vector in the bulk of gyromagnetic medium. It is shown that the gyromagnetic medium introduces a spin in the Poynting vector. The spin of the instantaneous Poynting vector and the relative strengths of the real and reactive power components are quantified using the Stokes plot method. Using this technique we investigate the presence of backward power propagation in a ferrite-filled waveguide. We present an analytical expression to locate the crossover point separating the forward and backward power propagation, where the real power propagation has a null. We further show that this backward power propagation leads to corresponding opposing surface currents on a waveguide plate of the ferrite-filled waveguide, while the potential difference between the two plates remain symmetric.

physics.optics↗

arXiv2021

Spin-governed topological surfaces and broken spin-momentum locking in a gyromagnetic medium

Topology of isofrequency surfaces plays a crucial role in characterizing the interaction of an electromagnetic wave with a medium. Thus, engineering the topology in complex media is leading to novel applications, ranging from super-resolution microscopy with hyperbolic metamaterials to sub-wavelength waveguiding structures. Here, we investigate the spin-governed nature of isofrequency surfaces in a general gyromagnetic medium. We show that gyrotropy also plays an important role in the topological properties of a medium, along with the anisotropic permeability and permittivity. Even though the topology primarily depends on permeability, gyrotropy can suppress or support the existence of certain topological surfaces. We reveal the connection between the gyrotropy imposed constraints and the photonic spin-profile of the topological surfaces. The spin-profile along the isofrequency surface is locked to the material, resulting in the non-reciprocity and breaking of the spin-momentum locking in the gyromagnetic medium. Further, we show that the conflict between spin-momentum locking and material locked spin leads to asymmetric mode profile and gyrotropy-induced cutoff in guided wave structures. Our work provides important insights into the underlying link between topology, spin, and non-reciprocity in gyrotropic media.

physics.optics↗