Third-order nonlinearity with subradiance dark-state in ultra-strong excitons and surface plasmon coupling using self-antiaggregation organic dye

Ahmad Khushaini, M. A., Azeman, N. H., Tg Abdul Aziz, T. H., Bakar, A. A. A., De La Rue, R. M. , Md Zain, A. R., Majlis, B. Y. and TH Tee, C. A. (2023) Third-order nonlinearity with subradiance dark-state in ultra-strong excitons and surface plasmon coupling using self-antiaggregation organic dye. Physica Scripta, 98(5), 055501. (doi: 10.1088/1402-4896/acc69b)

Abstract

A strong coupling regime with dressed states is formed when a propagating surface plasmon (PSP) mode coherently exchanges energy with an ensemble of excitons at a rate faster than the system's losses. These states are superpositions of superradiance excitons and PSP modes, accompanied by remaining subradiance or 'dark' exciton states. Dark-states are ubiquitous, especially in disordered systems, and they rise in number as the number of excitons increases. Here, the ultra-strong coupling regime was experimentally observed with the coupling strength to bare energy as high as g/${E}_{exciton}\,$∼ 0.23 using a self-antiaggregation organic dye, BOBzBT2 in an Otto-SPR configuration. We show that the hybrid system of excitons in a nonlinear organic dye layer and a PSP mode can be described by employing dark-state in a theory of nonlinear third-order sum-frequency generation (TSFG). Close agreement between the theory and the experiment has been demonstrated. The study opens up a new perspective for establishing a relationship between the optical properties of a third-order nonlinear material and the extent of strong coupling.

• Item Type: Articles
• Additional Information: This work was financially supported by the Ministry of Higher Education (MoHE) of Malaysia through fundamental research grant initiative (grant numbers FRGS/1/2022/STG05/UKM/02/4).
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: De La Rue, Professor Richard
• Authors: Ahmad Khushaini, M. A., Azeman, N. H., Tg Abdul Aziz, T. H., Bakar, A. A. A., De La Rue, R. M., Md Zain, A. R., Majlis, B. Y., and TH Tee, C. A.
• College/School: College of Science and Engineering > School of Engineering
• Journal Name: Physica Scripta
• Publisher: IOP Publishing
• ISSN: 0031-8949
• ISSN (Online): 1402-4896
• Published Online: 31 March 2023
• Copyright Holders: Copyright © 2023 The Author(s)
• First Published: First published in Physica Scripta 98(5):055501
• Publisher Policy: Reproduced under a Creative Commons license