Strong Coupling in a Self-Coupled Terahertz Photonic Crystal

Abstract

Vibrational strong coupling is a phenomenon in which a vibrational transition in a material placed inside a photonic structure is hybridized with its optical modes to form composite light–matter excitations known as vibro-polaritons. Here we demonstrate a new concept of vibrational strong coupling: we show that a monolithic photonic crystal, made of a resonant material, can exhibit strong coupling between the optical modes confined in the structure and the terahertz vibrational excitations of the same material. We study this system both experimentally and numerically to characterize the dispersion of the photonic modes for various sample thicknesses and reveal their coupling with the vibrational resonances. Finally, our time-domain THz measurements allow us to isolate the free induction decay signal from the grating modes as well as from the vibro-polaritons.

Perfect Absorption and Strong Coupling in Supported MoS2 Multilayers

“…In the strong coupling or polaritonic regime of light–matter interactions, the material excitation (in our case exciton) exchanges energy with the photonic mode faster than the individual subsystem decay rates. , This generates light–matter hybrid states called exciton-polaritons with new eigenenergies and decay rates, which potentially may be used for nonlinear optics applications, as well as for modification of material properties . Following these ideas, exciton-polaritons in TMDs have been realized using external optical resonators, such as Fabry-Pérot (FP) microcavities and plasmonic nanoparticles. − Recently, however, polaritons have been also realized by hybridizing excitons with photonic modes supported by the structure and three-dimensional geometry of the material itself. − Such cavity-free exciton-polaritons have been experimentally observed in TMDs by coupling to self-sustained FP and Mie resonances, − as well as to planar waveguide modes. − However, observation of strong coupling and perfect absorption in the same structure has not been reported to date.…”

All-optical control of phase singularities using strong light-matter coupling

“…When the coupling strength is sufficiently high the light and matter modes enter the strong coupling regime, forming hybrid states known as polaritons [2]. While most strong coupling experiments rely on external structures (such as planar microcavities [1,23] or plasmonic nanostructures [2]) to generate confined electromagnetic fields, our results build on recent work which shows that such structures are not always needed [18,19,20,21]. We use such a cavity-free design here to observe phase singularities associated with each newly created polariton state.…”

“…Many nanophotonic structures have been designed to generate phase singularities [6,7,8,9] for use in sensing [10,11,12,13,14,15,16] and optoelectronics [17]. We utilise the concept of cavity-free strong coupling [18,19,20,21], where electromagnetic modes sustained by a material are strong enough to strongly couple to the material's own molecular resonance, to create phase singularities in a simple thin film of organic molecules. We show that the use of photochromic molecules allows for all-optical control of phase singularities.…”

Water-Induced Tuning of the Emission of Polyaniline LEDs within the NIR to Vis Range

“… 3 The energy transfer to the coupled protonic system 37 − 39 is fast and effective enough so that the light emission from an excited protonic system 24 takes place as a competitive process, which is similar in mechanism to the generation of polaritons owing to strong coupling, when the resonant energy exchange between a confined optical mode and a material transition is faster than any decay process. 44 In consequence, the loss of energy is lower than in the case of the excited polyaniline electronic states. This results in a blue-shifted spectrum and more intensive light emission.…”

“…In addition, there is no pure n−π transition identified in polyaniline, and the spectral range considered corresponds to CT and polaron bands. , This indicates another mechanisman effective transfer of the excitation energy (originally provided by the electric current) from the electron system of polyaniline into the protonic one . The energy transfer to the coupled protonic system − is fast and effective enough so that the light emission from an excited protonic system takes place as a competitive process, which is similar in mechanism to the generation of polaritons owing to strong coupling, when the resonant energy exchange between a confined optical mode and a material transition is faster than any decay process . In consequence, the loss of energy is lower than in the case of the excited polyaniline electronic states.…”