Seminar

Abstract:  After a very brief overview of beam shifts and  bound states in continuum (BIC) [1], the route from leaky Berreman modes to BIC will be traced in a symmetric polar dielectric stratified medium [2]. The importance of epsilon near zero (ENZ) condition will be highlighted. Studies with p-polarized plane waves are extended to a generic vector beams using the formalism of Bliokh et al [3] avoiding strong paraxial approximation. This enables the theory and results to hold for beams at normal incidence as well as beams with larger k-spread. The theory is applied to calculate the beam shapes and centroids to infer on the in-plane and out of plane shifts, when structure supports a quasi-BIC (very close to BIC condition) [4]. The large field enhancement and strong localization mediated by the quasi-BIC are shown to lead to a dramatic enhancement in the in-plane Goos-Hänchen (GH) shift. For incident p-polarized beam, the reflected beam is shown to undergo large distortion amounting to a splitting, which is explained by a near perfect destructive interference of the left and right lobes of the momentum domain spectra. The transmitted beam retains its shape undergoing giant shifts comparable to the beam spot size. For incident circularly polarized light, the Imbert-Feodorov shift is nominal though with signature enhancement due to the BIC.

About the speaker: Prof. Subhasish Dutta Gupta is Honorary Professor at University of Hyderabad and Adjunct Professor, Tata Institute for Fundamental Research Research Adjunct Professor, IISER, Kolkata. His main research interests are in theoretical optics, plasmonics, nano-optics, quantum and nonlinear optics.

References:

[1] Chia Wei Hsu, et al., Nature Reviews Materials, 1, 16048 (2016).

[2] G. Remesh, et al., Optics Communications, 498, 127223 (2021)

[3] K.Y. Bliokh, et al., Journal of Optics, 15, 014001 (2013)

[4] S.S. Biswas, et al.,J. Opt. (in press, 2023), https://doi.org/10.1088/2040-8986/acd391