Continuously-tunable light–matter coupling in optical microcavities with 2D semiconductors

Abstract

A theoretical variation between the two distinct light–matter coupling regimes, namely weak and strong coupling, becomes uniquely feasible in open optical Fabry—Pérot microcavities with low mode volume, as discussed here. In combination with monolayers of transition-metal dichalcogenides (TMDCs) such as WS2, which exhibits a large exciton oscillator strength and binding energy, the room-temperature observation of hybrid bosonic quasiparticles, referred to as exciton–polaritons and characterized by a Rabi splitting, comes into reach. In this context, our simulations using the transfer-matrix method show how to tailor and alter the coupling strength actively by varying the relative field strength at the excitons’ position – exploiting a tunable cavity length, a transparent PMMA spacer layer and angle-dependencies of optical resonances. Continuously tunable coupling for future experiments is hereby proposed, capable of real-time adjustable Rabi splitting as well as switching between the two coupling regimes. Being nearly independent of the chosen material, the suggested structure could also be used in the context of light–matter-coupling experiments with quantum dots, molecules or quantum wells. While the adjustable polariton energy levels could be utilized for polariton-chemistry or optical sensing, cavities that allow working at the exceptional point promise the exploration of topological properties of that point.

Microcavity phonon polaritons from the weak to the ultrastrong phonon–photon coupling regime

“…4c). A larger coupling strength can also be achieved for the second cavity mode by distributing the hBN layer near the positions where the intensity of this mode is maximum 52 (we discuss the dependence of the coupling strength on the layer position in Supplementary Note 7). Interestingly, the coupling strength g for both the first and second cavity mode can be well approximated by an analytical expression obtained by a microscopic theory that is described in Supplementary Note 6.…”

Tunable Polymer/Air‐Bragg Optical Microcavity Configurations for Controllable Light–Matter Interaction Scenarios

“…Based on theoretical data and considerations with chosen design parameters, reflectivity spectra toward strong light-matter coupling with a virtual 2D semiconductor inside the cavity were equally obtained. The optical properties such as reflection, transmission, and angle-resolved spectra of multilayered open cavity structures were calculated using the TMM-based simulation code as used in Wall et al [46]…”

“…Note that longer wavelengths, e.g., for a nearinfrared to infrared intralayer or interlayer excitonic species in TMDC monolayers or 2D heterostructures, respectively, provide more favorable printing conditions than for the here-chosen WS 2 A-exciton resonance. For detailed explanations regarding the TMM, we refer the reader to the Supporting Information of our previous work by Wall et al [46] Figure 2a-d shows the stopband of an air-Bragg reflector with different layer pair numbers, for four different layer thickness configurations, considering the design wavelength (λ) to be around 620 nm in air (2.0 eV). The air-Bragg reflector with λ/4 layer thickness exhibits a reflectivity close to 1 over a 100 nm range when composed of eight mirror pairs (of air and IP-DIP).…”

“…[40][41][42] Among the various designs, those highly versatile, spectrally tunable, and relatively simple open-cavity configurations have already covered a large spectrum of applications ranging from cavity quantum electrodynamics (CQED) [7,43] to (fibercoupled) optoelectronical or optomechanical devices [34,44,45] as well as sensors. [46][47][48] Many different and unique approaches have been already demonstrated to improve the confinement of the light and functionality of cavity systems. [1,3] Some approaches such as photonic crystal membranes and whispering gallery modes do provide significant confinement of light in all the three spatial dimensions, whereas open-cavity configurations with an air-gapped microresonator such as fiber-based FP cavities provide intrinsic tunability in both the spectral and spatial domains [10,34,45,46,49] as flexible light-matter interfaces.…”

“…[46][47][48] Many different and unique approaches have been already demonstrated to improve the confinement of the light and functionality of cavity systems. [1,3] Some approaches such as photonic crystal membranes and whispering gallery modes do provide significant confinement of light in all the three spatial dimensions, whereas open-cavity configurations with an air-gapped microresonator such as fiber-based FP cavities provide intrinsic tunability in both the spectral and spatial domains [10,34,45,46,49] as flexible light-matter interfaces. Often, a top-down nanotechnology approach is used to define precise (monolithic) resonator structures, or movable reflectors are combined to form tunable open resonators.…”