Exciton–Photonics: From Fundamental Science to Applications

Abstract

Semiconductors in all dimensionalities ranging from 0D quantum dots and molecules to 3D bulk crystals support bound electron-hole pair quasiparticles termed as excitons. Over the past two decades, the emergence of a variety of low-dimensional semiconductors that support excitons combined with advances in nano-optics and photonics has burgeoned a new area of research that focuses on engineering, imaging, and modulating coupling between excitons and photons, resulting in the formation of hybrid-quasiparticles termed exciton-polaritons. This new area has the potential to bring about a paradigm shift in quantum optics, as well as classical optoelectronic devices. Here, we present a review on the coupling of light in excitonic semiconductors and investigation of the unique properties of these hybrid quasiparticles via both farfield and near-field imaging and spectroscopy techniques. Special emphasis is laid on recent advances with critical evaluation of the bottlenecks that plague various materials towards practical device implementations including quantum light sources.Our review highlights a growing need for excitonic materials development together with optical engineering and imaging techniques to harness the utility of excitons and their host materials for a variety of applications.

Nonlinear Exciton‐Mie Coupling in Transition Metal Dichalcogenide Nanoresonators

“…Another advantage of TMDCs is their excitonic nature of dielectric response, [16,32] which greatly enhances light-matter interaction. [33] Specifically, this leads to an increase in harmonic generation due to resonances of nonlinear susceptibilities in the spectral vicinity of excitons both in the monolayer [34,35] and bulk [36] of TMDCs. As a result, combining Mie-type resonances with TMDC excitons could result in significant harmonic generation.…”

Theoretical Study on the Contacting Interface-Dependent Band Alignments of CsPbBr3@MoS2 van der Waals Heterojunctions: Spin–Orbit Coupling Does Matter

“…Organic–inorganic hybrid perovskites (e.g., CH 3 NH 3 PbI 3 ) have been considered to be one of the most promising materials for the development of next-generation solar cells since the seminal work of Kojima et al in 2009 . Up until now, the power conversion efficiency of organic–inorganic hybrid perovskite solar cells has reached a record-high value of 25.5%, which can be attributed to their strong visible light absorption, high carrier mobility, and long electron–hole diffusion length. ,− In addition to solar cells, these perovskites also have potential applications in fields such as photodetectors, phototransistors, photocatalysis, and so on. − However, the poor stability of these organic–inorganic hybrid perovskites under ambient conditions severely impedes their future commercialization. − In order to improve the stability of the perovskites against light, heat, and humidity, all-inorganic cesium lead halide perovskites CsPbX 3 (X = Cl, Br, and I) are developed, in which the organic cations such as [CH 3 NH 3 ] + in organic–inorganic hybrid perovskites are replaced by inorganic Cs + cations. , Apart from the much enhanced stability, CsPbX 3 perovskites also retain some excellent optoelectronic properties which are comparable to their organic–inorganic counterparts. Therefore, these novel all-inorganic perovskites have also attracted great attention in recent years. − …”

Ultrastable tip-enhanced hyperspectral optical nanoimaging for defect analysis of large-sized WS 2 layers

“…The TERS image is slightly shifted with respect to the AFM image, because the AFM and TERS image were measured separately; however, it does not affect our analysis of the TERS image here. The scan area was 1 μm by 4 μm, which is at least four times larger than typical TERS images of 2D materials recorded by conventional AFM-based TERS systems, while the step size was set to 10 nm, which is similar or smaller than sizes used in typical TERS and TEPL images of 2D materials ( 45 , 46 ). It should be noted that optical nanoimaging of 2D materials in relatively large area may be performed by either significantly increasing the measurement step size to more than 30 nm, which will deteriorate the spatial resolution, or by using relatively high excitation power.…”