Northwestern Events Calendar

May
28
2021

Colloquium: Thomas Searles: Tunable Strong Coupling in Terahertz Metasurfaces

When: Friday, May 28, 2021
4:00 PM - 5:00 PM Central

Where: Online

Audience: Faculty/Staff - Student - Post Docs/Docs - Graduate Students

Contact: Samantha Westlake   (847) 491-7650

Group: Physics and Astronomy Colloquia

Category: Academic

Description:

Abstract: Recently, the study of ultrastrong light-matter coupling has gained increased interest due to its potential application in optoelectronics, plasmonics and circuit quantum electrodynamics. One common way to achieve strong coupling is to place an emitter near or inside an optical cavity. In this case, the emitter?cavity system, the spatial overlap between the emitters and the cavity is often the key factor that limits the light?matter coupling strength. The cavities can be either photonic microcavities, which can have very high quality factors, or surface plasmon resonators, whose mode volume can be in the deep subwavelength regime. In contrast to microcavities, where the light field is confined by two metallic layers or dielectric mirrors, an alternative approach to achieve strong coupling is provided by metamaterials (MMs) in which the confinement is provided by the evanescent field of localized plasmons. This has led to the demonstration of strong-coupling regime with a number of quantum systems including phonons, intersubband transitions and cyclotron resonances. In addition, resonant coupling leads to light?matter hybridization into two normal modes with an energy separation known as the vacuum Rabi splitting (VRS).

In this work, we investigate a THz planar metamaterial and observe the excitation of a polaritonic state as well as a VRS with a coupling strength of ~21%. Strong splitting results in the formation of a forbidden frequency gap that can be evaluated as a transparency window caused by the hybridization of two eigenmodes. The physics of the transparency window is analogous to the lattice induced transparency effect in which there are limited demonstrations in the literature of strong coupling due to cavity-cavity interactions. Further, we show that by increasing the capacitive gap width of the MM unit cell, we increase the overall capacitance of the MM and demonstrate an anti-crossing behavior; a key signature to strong-light matter coupling. Lastly, we present new results for the formation of bound states in the continuum driven in a THz metasurface by varying the polarization with experimental evidence supporting numerical simulations for the tunabnility of capacitive-mediated strong coupling.

Seminar Speaker: Professor Thomas Searles, Howard University

Host: Jens Koch

Meeting Details:
Friday, May 28, 2021 at 4:00 pm (Central Time) on Zoom.

Zoom info:
Please email samantha.westlake@northwestern.edu if you would like access to the Zoom meeting link.

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