Monolayer transition metal dichalcogenides integrated in optical microcavities host exciton-polaritons as a hallmark of the strong light-matter coupling regime. Analogous concepts for hybrid light-matter systems employing spatially indirect excitons with a permanent electric dipole moment in heterobilayer crystals promise realizations of exciton-polariton gases and condensates with inherent dipolar interactions. Here, we implement cavity-control of interlayer excitons in vertical MoSe 2 -WSe 2 heterostructures. Our experiments demonstrate the Purcell effect for heterobilayer emission in cavity-modified photonic environments, and quantify the light-matter coupling strength of interlayer excitons. The results will facilitate further developments of dipolar exciton-polariton gases and condensates in hybrid cavity – van der Waals heterostructure systems.

Colloidal semiconductor nanoplatelets exhibit quantum size effects due to their thickness of only a few monolayers, together with strong optical band-edge transitions facilitated by large lateral extensions. In this article, we demonstrate room temperature strong coupling of the light and heavy hole exciton transitions of CdSe nanoplatelets with the photonic modes of an open planar microcavity. Vacuum Rabi splittings of 66 ± 1 meV and 58 ± 1 meV are observed for the heavy and light hole excitons, respectively, together with a polariton-mediated hybridization of both transitions. By measuring the concentration of platelets in the film, we compute the transition dipole moment of a nanoplatelet exciton to be μ = (575 ± 110) D. The large oscillator strength and fluorescence quantum yield of semiconductor nanoplatelets provide a perspective toward novel photonic devices by combining polaritonic and spinoptronic effects.

tuned simply by changing their size, such that any emission wavelength in the visible and near infrared of the spectrum can be accessed with a small selection of materials. Several nanocrystal based lasers have now been reported with a variety of device designs. [2][3][4][5][6][7][8][9] Some of these demonstrations have utilized solid fi lms of pure closely packed NQDs [ 3,[5][6][7]9 ] or mixed with titania for better wave-guiding properties. [ 2 ] Others have coated the NQDs onto microtoroids and microspheres to take advantage of the whispering gallery mode structure. [ 4,8 ] Understanding the interplay between the various absorption and emission processes is essential in order to optimize the nanocrystal design. Spectroscopy of the gain produced can be performed using pump-probe techniques [ 10 ] and allows the investigation of exciton relaxation dynamics. However, these rapid transient processes are considerably removed from lasing behavior in the presence of optical feedback and a good understanding of the lasing process is currently lacking.In this paper, we report a convenient method for the direct investigation of the lasing behavior of solution-based NQDs by performing gain spectroscopy enabled via in situ tuning of the cavity feedback wavelength. Tunable cavities and laser emission have been demonstrated by others using various methods. For example, the cavity resonance can be tuned by external heating achieved through either modulating the pump power [ 8 ] or by directly heating the cavity using an electrical heater. [ 11 ] Other methods have utilized strain, [ 12 ] electric-fi eld, [ 13,14 ] or pressure. [ 15 ] However, these methods tend to either have too limited a tuning range for useful spectroscopy, or involve changes to the NQD environment that may themselves modify the gain characteristics, making interpretation of the observed changes in lasing performance diffi cult. By directly tuning the cavity length of a Fabry-Perot style open resonator, we achieve both a wide tuning range and fi ne control limited only by the resolution of the actuator. As a result we are able to observe single mode lasing over a range exceeding 25 nm, and thereby map the spectra for the lasing threshold and differential gain. The NQDs in solution within the cavity experience no change in temperature or stress during tuning and so the changes in lasing performance can be attributed unambiguously to the change in feedback wavelength. From a technological standpoint, our results demonstrate a new approach to widely tunable single mode lasers for chip-scale and low power applications.