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We study the dynamics of multimode polariton lasing in organic microcavities by using a second-order cumulant equation approach. By inspecting the time evolution of the photon mode occupations, we show that if multiple lasing peaks are observed in time-integrated mode occupations, the reason can be either bi-modal lasing or temporal switching between several modes. The former takes place within a narrow range of parameters while the latter occurs more widely. We find that the origin of the temporal switching is different in the weak- and strong-coupling regimes. At weak coupling slope efficiency is the determining factor, while for strong coupling it is changes in the eigenmodes and gain spectrum upon pumping. This difference is revealed by investigating the photoluminescence and momentum-resolved gain spectra. Our results underscore the importance of understanding the time evolution of the populations when characterizing the lasing behaviour of a multimode polariton system, and show how these features differ between weak and strong coupling., Comment: 15 pages, 13 figures

Bosonic condensates offer exciting prospects for studies of non-equilibrium quantum dynamics. Understanding the dynamics is particularly challenging in the sub-picosecond timescales typical for room temperature luminous driven-dissipative condensates. Here we combine a lattice of plasmonic nanoparticles with dye molecule solution at the strong coupling regime, and pump the molecules optically. The emitted light reveals three distinct regimes: one-dimensional lasing, incomplete stimulated thermalization, and two-dimensional multimode condensation. The condensate is achieved by matching the thermalization rate with the lattice size and occurs only for pump pulse durations below a critical value. Our results give access to control and monitoring of thermalization processes and condensate formation at sub-picosecond timescale., Comment: Revised version

openaire: EC/H2020/745115/EU//OPLD Organic light-emitting diodes (OLEDs) have been established as versatile light sources that allow for easy integration in large-area surfaces and flexible substrates. In addition, the low fabrication cost of OLEDs renders them particularly attractive as general lighting sources. Current methods for the fabrication of white-light OLEDs rely on the combination of multiple organic emitters and/or the incorporation of multiple cavity modes in a thick active medium. These architectures introduce formidable challenges in both device design and performance improvements, namely, the decrease of efficiency with increasing brightness (efficiency roll-off) and short operational lifetime. Here we demonstrate, for the first time, white-light generation in an OLED consisting of a sub-100 nm thick blue single-emissive layer coupled to the photonic Bragg modes of a dielectric distributed Bragg reflector (DBR). We show that the Bragg modes, although primarily located inside the DBR stack, can significantly overlap with the emissive layer, thus efficiently enhancing emission and outcoupling of photons at selected wavelengths across the entire visible light spectrum. Moreover, we show that color temperature can be tuned by the DBR parameters, offering great versatility in the optimization of white-light emission spectra.

We report on reversible all-optical emission control and lasing in plasmonic nanoparticle lattices. By incorporating photochromic molecules into the liquid gain medium composed of organic fluorescent molecules, we realize all-optical control over gain and absorption, the two key parameters associated with both conventional and nanoscale lasing. We demonstrate reversible photoswitching between two distinct modes of operation: (1) spontaneous emission to the lattice mode, characterized by broad emission line width, low emission intensity, and large angular distribution; and (2) lasing action, characterized by very narrow (sub-nm) line widths due to the emergence of increased gain and temporal coherence in the system, approximately 3 orders of magnitude increase in emission intensity, and narrow 0.7° angular divergence of the beam. A rate-equation model is employed to describe the operation of the switchable plasmonic laser. Our results provide the first demonstration of optically tunable losses in plasmonic lattice lasers, which is an important milestone for the development of active plasmonics and paves the way for ultrafast all-optical switching of plasmonic nanolasers. acceptedVersion

We present a beyond-mean-field approach to predict the nature of organic polariton lasing, accounting for all relevant photon modes in a planar microcavity. Starting from a microscopic picture, we show how lasing can switch between polaritonic states resonant with the maximal gain, and those at the bottom of the polariton dispersion. We show how the population of non-lasing modes can be found, and by using two-time correlations, we show how the photoluminescence spectrum (of both lasing and non-lasing modes) evolves with pumping and coupling strength, confirming recent experimental work on the origin of blueshift for polariton lasing., 6 pages, 4 figures, plus supplemental material

openaire: EC/H2020/745115/EU//OPLD Bose–Einstein condensation is a remarkable manifestation of quantum statistics and macroscopic quantum coherence. Superconductivity and superfluidity have their origin in Bose–Einstein condensation. Ultracold quantum gases have provided condensates close to the original ideas of Bose and Einstein, while condensation of polaritons and magnons has introduced novel concepts of non-equilibrium condensation. Here, we demonstrate a Bose–Einstein condensate of surface plasmon polaritons in lattice modes of a metal nanoparticle array. Interaction of the nanoscale-confined surface plasmons with a room-temperature bath of dye molecules enables thermalization and condensation in picoseconds. The ultrafast thermalization and condensation dynamics are revealed by an experiment that exploits thermalization under propagation and the open-cavity character of the system. A crossover from a Bose–Einstein condensate to usual lasing is realized by tailoring the band structure. This new condensate of surface plasmon lattice excitations has promise for future technologies due to its ultrafast, room-temperature and on-chip nature.

I review our recent findings on lasing / condensation in plasmonic nanoparticle lattices1-5. The system properties can be tailored with high precision, including the lasing / condensation energies, linewidths, as well as the dimensionality of the feedback. For a 2-dimensional (2-D) square lattice, we identify lasing in the bright and the dark mode of the system1. By reducing the dimensionality to 1-D we observe the dark mode lasing2. In broken symmetry 2-dimensional rectangular lattices, we observe multimode lasing3. In honeycomb lattices with hexagonal symmetry, we observe 6 beams with specific off-normal angles and polarization properties corresponding to six-fold symmetry of such a lattice4. Finally, I review our recent studies in plasmonic Bose-Einstein condensation in plasmonic lattices5.

Strong coupling between quantum emitters and surface plasmon polariton modes in metal nanostructures has been extensively studied in recent years. A natural direction of research and a prerequisite for many applications is the possibility of external, in situ manipulation of the strength of the coupling. We review research on active control of surface plasmon–emitter strong coupling phenomena. Active control has been demonstrated for a variety of systems, such as metal nanohole arrays, nanoparticles, rods and dimers, combined with photochromic molecules, J-aggregates, and monolayers of MoS2, WS2, and WSe2. We discuss work on optical switching realized by changing photochromic molecules by UV and visible light between forms that couple strongly or weakly with the electromagnetic field mode of the plasmonic nanostructure. Other forms of optical control such as use of polarization and phase are briefly covered. We review research on electrical, thermal, and chemical active control of light–matter coupling in plasmonic systems.

Lasing at the nanometre scale promises strong light-matter interactions and ultrafast operation. Plasmonic resonances supported by metallic nanoparticles have extremely small mode volumes and high field enhancements, making them an ideal platform for studying nanoscale lasing. At visible frequencies, however, the applicability of plasmon resonances is limited due to strong ohmic and radiative losses. Intriguingly, plasmonic nanoparticle arrays support non-radiative dark modes that offer longer life-times but are inaccessible to far-field radiation. Here, we show lasing both in dark and bright modes of an array of silver nanoparticles combined with optically pumped dye molecules. Linewidths of 0.2 nanometers at visible wavelengths and room temperature are observed. Access to the dark modes is provided by a coherent out-coupling mechanism based on the finite size of the array. The results open a route to utilize all modes of plasmonic lattices, also the high-Q ones, for studies of strong light-matter interactions, condensation and photon fluids., Comment: Accepted for publication in Nature Communications