Room Temperature Polariton Lasing Research Articles

Dirac Cones and Room Temperature Polariton Lasing Evidenced in an Organic Honeycomb Lattice.

Artificial 1D and 2D lattices have emerged as a powerful platform for the emulation of lattice Hamiltonians, the fundamental study of collective many-body effects, and phenomena arising from non-trivial topology. Exciton-polaritons, bosonic part-light and part-matter quasiparticles, combine pronounced nonlinearities with the possibility of on-chip implementation. In this context, organic semiconductors embedded in microcavities have proven to be versatile candidates to study nonlinear many-body physics and bosonic condensation, and in contrast to most inorganic systems, they allow the use at ambient conditions since they host ultra-stable Frenkel excitons. A well-controlled, high-quality optical lattice is implemented that accommodates light-matter quasiparticles. The realized polariton graphene presents with excellent cavity quality factors, showing distinct signatures of Dirac cone and flatband dispersions as well as polariton lasing at room temperature. This is realized by filling coupled dielectric microcavities with the fluorescent protein mCherry. The emergence of a coherent polariton condensate at ambient conditions are demonstrated, taking advantage of coupling conditions as precise and controllable as in state-of-the-art inorganic semiconductor-based systems, without the limitations of e.g. lattice matching in epitaxial growth. This progress allows straightforward extension to more complex systems, such as the study of topological phenomena in 2D lattices including topological lasers and non-Hermitian optics.

Polarized room-temperature polariton lasing in elliptical microcavities filled with fluorescent proteins

Organic exciton-polaritons, which arise from the strong light-matter coupling between excitons in organic molecules and cavity photons, have emerged as a versatile platform for the investigation of polariton lasing, Bose-Einstein condensation and many-body phenomena at ambient conditions. Here, we study the condensation of exciton-polaritons in fluorescent protein-filled microcavities with elliptical cross-sections. The structural anisotropy of these cavities yields a distinct optical polarization splitting, which we investigate both experimentally and numerically. In the high-density regime of exciton-polaritons, the pronounced polarization splitting of the fundamental polaritonic resonance enforces selective condensation in one linearly polarized polaritonic mode. Our findings constitute a solid basis for polarization engineering in room-temperature polariton condensates.

Room-temperature polariton lasing in GaN microrods with large Rabi splitting.

Room-temperature polariton lasing is achieved in GaN microrods grown by metal-organic vapor phase epitaxy. We demonstrate a large Rabi splitting (Ω = 2g0) up to 162 meV, exceeding the results from both the state-of-the-art nitride-based planar microcavities and previously reported GaN microrods. An ultra-low threshold of 1.8 kW/cm2 is observed by power-dependent photoluminescence spectra, with the linewidth down to 1.31 meV and the blue shift up to 17.8 meV. This large Rabi splitting distinguishes our coherent light emission from a conventional photon lasing, which strongly supports the preparation of coherent light sources in integrated optical circuits and the study of exciting phenomena in macroscopic quantum states.

Low Threshold Room Temperature Polariton Lasing from Fluorene‐Based Oligomers

AbstractOrganic semiconductors possessing tightly bound Frenkel excitons are known to be attractive candidates for demonstrating polariton lasing at room temperature. As polariton lasing can occur without inversion, it is a potential route to very low threshold coherent light sources. However, so far, the thresholds of organic polariton lasers have generally been much higher than those of organic photon lasers. Here this problem has been addressed by investigating two new organic molecules with a structure combining fluorene and carbazole groups. The materials are readily deposited from solution and exhibit high photoluminescence quantum yields, high absorption coefficients, and large radiative decay rates in neat films. Room temperature polariton lasing is realized in both materials with incident thresholds of 13.5 and 9.7 µJ cm−2, corresponding to absorbed thresholds of 3.3 and 2.2 µJ cm−2, respectively. These are the lowest values reported to date for polariton lasing in organic semiconductor materials, and approach typical values for organic photon lasers. The step‐like power dependent blue‐shift of polariton modes indicates an interplay between different depletion channels of the exciton reservoir. This work brings practical room temperature polaritonic devices and future realization of electrically driven polariton lasers a step closer.

Low-threshold polariton lasing in a highly disordered conjugated polymer

Low-threshold, room-temperature polariton lasing is crucial for future application of polaritonic devices. Conjugated polymers are attractive candidates for room-temperature polariton lasers, due to their high exciton binding energy, very high oscillator strength, easy fabrication, and tunability. However, to date, polariton lasing has only been reported in one conjugated polymer, ladder-type MeLPPP, whose very rigid structure gives an atypically narrow excitonic linewidth. Here, we observe polariton lasing in a highly disordered prototypical conjugated polymer, poly(9,9-dioctylfluorene), thereby opening up the field of polymer materials for polaritonics. The long-range spatial coherence of the emission shows a maximum fringe visibility contrast of 72%. The observed polariton lasing threshold (27.7 μJ/cm2, corresponding to an absorbed pump fluence of 19.1 μJ/cm2) is an order of magnitude smaller than for the previous polymer polariton laser, potentially bringing electrical pumping of such devices a step closer.

Organic Polariton Lasing and the Weak to Strong Coupling Crossover.

Following experimental realizations of room temperature polariton lasing with organic molecules, we present a microscopic model that allows us to explore the crossover from weak to strong matter-light coupling. We consider a nonequilibrium Dicke-Holstein model, including both strong coupling to vibrational modes and strong matter-light coupling, providing the phase diagram of this model in the thermodynamic limit. We discuss the mechanism of polariton lasing, uncovering a process of self-tuning, and identify the relation and distinction between regular dye lasers and organic polariton lasers.

Room-Temperature Polariton Lasing in All-Inorganic Perovskite Nanoplatelets.

Polariton lasing is the coherent emission arising from a macroscopic polariton condensate first proposed in 1996. Over the past two decades, polariton lasing has been demonstrated in a few inorganic and organic semiconductors in both low and room temperatures. Polariton lasing in inorganic materials significantly relies on sophisticated epitaxial growth of crystalline gain medium layers sandwiched by two distributed Bragg reflectors in which combating the built-in strain and mismatched thermal properties is nontrivial. On the other hand, organic active media usually suffer from large threshold density and weak nonlinearity due to the Frenkel exciton nature. Further development of polariton lasing toward technologically significant applications demand more accessible materials, ease of device fabrication, and broadly tunable emission at room temperature. Herein, we report the experimental realization of room-temperature polariton lasing based on an epitaxy-free all-inorganic cesium lead chloride perovskite nanoplatelet microcavity. Polariton lasing is unambiguously evidenced by a superlinear power dependence, macroscopic ground-state occupation, blueshift of the ground-state emission, narrowing of the line width and the buildup of long-range spatial coherence. Our work suggests considerable promise of lead halide perovskites toward large-area, low-cost, high-performance room-temperature polariton devices and coherent light sources extending from the ultraviolet to near-infrared range.

Room temperature polariton lasing vs photon lasing in a ZnO-based hybrid microcavity

We report on the room temperature polariton lasing and photon lasing in a ZnO-based hybrid microcavity under optical pumping. A series of experimental studies of the polariton lasing (exciton-photon detunings of δ = -119 meV) in the strong-coupling regime are discussed and compared to a photon lasing (δ = -45 meV) in the weak-coupling regime obtained in the same structure. The measured threshold power density (31.8 kW/cm2) of polariton lasing is one order of magnitude lower than that of the photon lasing (318.2 kW/cm2). In addition, the comparison between polariton lasing and photon lasing is done in terms of the linewidth broadening, blue-shift of the emission peak, and polarization.

Toward polariton lasing in a zinc oxide microcavity: Design and preliminary results

We report the observation of the strong coupling regime in a half ZnO cavity. A large Rabi splitting of 130 meV is seen as well as a bottleneck in the exciton-polariton relaxation due to a shorter cavity-photon lifetime. The deposition of the top mirror is expected to yield a Q factor of 620 and the structure would then fulfill the main criteria required for room temperature polariton lasing to occur. This conclusion is supported by simulations based on the solution of Boltzmann equations leading to a polariton density threshold of 1016 cm−3.

Theory of exciton-polariton lasing at room temperature in ZnO microcavities

We use the semiclassical Boltzmann equations to describe the exciton-polariton relaxation in a bulk ZnO microcavity at room temperature. We present kinetic phase diagrams which report the lasing threshold versus the main sample parameters, such as the polariton lifetime or the value of the Rabi splitting. We find that the polariton laser is operating close to the thermodynamic equilibrium in most cases which makes advantageous the use of microcavities showing very large Rabi splittings as it is the case in ZnO structures. We find that room temperature polariton lasing could be observed in the samples presently available.