Thermalization and Cooling of Plasmon-Exciton Polaritons: Towards Quantum Condensation

Abstract

We present indications of thermalization and cooling of quasiparticles, a precursor for quantum condensation, in a plasmonic nanoparticle array. We investigate a periodic array of metallic nanorods covered by a polymer layer doped with an organic dye at room temperature. Surface lattice resonances of the array--hybridized plasmonic-photonic modes--couple strongly to excitons in the dye, and bosonic quasiparticles which we call plasmon-exciton polaritons (PEPs) are formed. By increasing the PEP density through optical pumping, we observe thermalization and cooling of the strongly coupled PEP band in the light emission dispersion diagram. For increased pumping, we observe saturation of the strong coupling and emission in a new weakly coupled band, which again shows signatures of thermalization and cooling.

Plasmon-exciton-polariton lasing

“…This threshold fluence is one of the lowest values observed in optically pumped organic polariton lasers [14][15][16] and also is lower than the reported threshold for plasmonic-based photon lasers in the weak coupling regime [20,40]. Note that in our experiments, photodegradation occurs before the transition to the weak coupling regime [23], so the appearance of photon lasing is precluded by the damage threshold. Moreover, it is interesting to note that below the threshold, the emission decreases as C increases.…”

“…This is in agreement with our measurements considering organic polariton interaction within the condensate. Similar to the extinction measurements shown earlier, we can use angular-resolved measurements to study PEP emission at increasing pump fluences as we approach the critical density of PEPs [23]. In Fig.…”

“…However, the subwavelength field enhancements generated by resonant metallic nanostructures can significantly boost the light-matter coupling. Indeed, strong plasmon-exciton coupling has already been observed [11,13,[22][23][24][25][26][27], but earlier attempts toward achieving plasmon-exciton-polariton (PEP) lasing remained unsuccessful due to the inefficient relaxation mechanism of PEPs and the saturation of strong coupling at large pumping fluences [23]. Here, we demonstrate PEP lasing from an optically pumped array of silver nanoparticles coated by a thin layer of organic molecules at room temperature, occurring at a low threshold [8].…”

Plasmonics of 2D Nanomaterials: Properties and Applications

“…The coupling effects between excitons and plasmons are widely found in many hybrid nanomaterial systems such as plasmonic nanoparticles and structures hybridized with J‐Aggregate or quantum dots 72, 73, 74, 75, 76, 77. For example, significant Rabi splitting is observed which reaches to hundreds of meV and reveals strong coupling effect between excitons and plasmons.…”

Breaking the Symmetry of Forward-Backward Light Emission with Localized and Collective Magnetoelectric Resonances in Arrays of Pyramid-Shaped Aluminum Nanoparticles

“…This coupling leads to hybrid plasmonicphotonic resonances known as surface lattice resonances (SLRs), with quality factors depending on the number of particles in the array [33]. SLRs have attracted interest for their tunable linewidths and dispersion [32,34,35], enhanced spontaneous emission [36][37][38][39][40], sensing [41,42], lasing [43], and strong coupling to molecules [44][45][46]. While previous studies focused on the diffractive coupling of particles with a dominant electric response, here we investigate light emission from a structure supporting diffractive coupling of particles with comparable electric and magnetic response.…”