Spatial photoluminescence and lifetime mappings of quasi-2D perovskites coupled with a dielectric metasurface.

Light-matter interaction between quantum emitters and optical cavities plays a vital role in fundamental quantum photonics and the development of optoelectronics. Resonant metasurfaces are proven to be an efficient platform for tailoring the spontaneous emission (SE) of the emitters. In this work, we study the interplay between quasi-2D perovskites and dielectric TiO2 metasurfaces. The metasurface, functioning as an open cavity, enhances electric fields near its plane, thereby influencing the emissions of the perovskite. This is verified through angle-resolved photoluminescence (PL) studies. We also conducted reflectivity measurements and numerical simulations to validate the coupling between the quasi-2D perovskites and photonic modes. Notably, our work introduces a spatial mapping approach to study Purcell enhancement. Using fluorescence lifetime imaging microscopy (FLIM), we directly link the PL and lifetimes of the quasi-2D perovskites in spatial distribution when positioned on the metasurface. This correlation provides unprecedented insights into emitter distribution and emitter-resonator interactions. The methodology opens a new (to the best of our knowledge) approach for studies in quantum optics, optoelectronics, and medical imaging by enabling spatial mapping of both PL intensity and lifetime, differentiating between uncoupled quantum emitters and those coupled with different types of resonators.

Coexistence of surface lattice resonances and bound states in the continuum in a plasmonic lattice.

We present a numerical study on a 2D array of plasmonic structures covered by a subwavelength film. We explain the origin of surface lattice resonances (SLRs) using the coupled dipole approximation and show that the diffraction-assisted plasmonic resonances and formation of bound states in the continuum (BICs) can be controlled by altering the optical environment. Our study shows that when the refractive index contrast Δn < -0.1, the SLR cannot be excited, while a significant contrast (Δn > 0.3) not only sustains plasmonic-induced resonances but also forms both symmetry-protected and accidental BICs. The results can aid the streamlined design of plasmonic lattices in studies on light-matter interactions and applications in biosensors and optoelectronic devices.

Doping-induced plateau of strong electromagnetic confinement in the momentum space.

In this Letter, we present a design strategy for the realization of electrically powered bound states in the continuum (BIC) lasers. Despite growing attention of the optics community for BICs, practical uses of BICs in an active device are still unestablished. A large index contrast and out-of-plane symmetries that aid the formation of BICs are not trivial to achieve using conventional approaches for semiconductor laser design. Here, we propose a doping scheme to circumvent this issue. We also show that the introduction of material absorption due to carriers deteriorates the quality factor of BIC modes and show that a suitable compromise between electrical conductivity and optical loss can be achieved.

Experimental demonstration of single-mode topological valley-Hall lasing at telecommunication wavelength controlled by the degree of asymmetry.

Topology plays a fundamental role in contemporary physics and enables new information processing schemes and wave device physics with built-in robustness. However, the creation of photonic topological phases usually requires complex geometries that limit the prospect for miniaturization and integration and dispossess designers of additional degrees of freedom needed to control topological modes on-chip. By controlling the degree of asymmetry (DoA) in a photonic crystal with broken inversion symmetry, we report single-mode lasing of valley-Hall ring cavities at telecommunication wavelength. The DoA governs four photon confinement regimes at the interface of topologically distinct valley-Hall domains and evidences an interplay between the width of the topological bandgap and the quality factor of ring-like modes for single-mode operation. Our results open the door to novel optoelectronic devices and systems based on compact topological integrated circuits.

Nonlinear Emission of Molecular Ensembles Strongly Coupled to Plasmonic Lattices with Structural Imperfections.

We demonstrate nonlinear emission from molecular layers strongly coupled to extended light fields in arrays of plasmonic nanoparticles in the presence of structural imperfections. Hybrid light-matter states, known as plasmon-exciton polaritons (PEPs), are formed by the strong coupling of Frenkel excitons in molecules to surface lattice resonances. These resonances result from the radiative coupling of localized surface plasmon polaritons in silver nanoparticles enhanced by diffraction on the array. By designing arrays with different lattice constants, we show that the nonlinear emission frequency is solely determined by the relaxation of exciton polaritons through vibrational quanta in the molecules. We also observe long-range spatial coherence in the samples, which supports the explanation in terms of a nonlinear collective emission of strongly coupled PEPs. In contrast to recent observations of exciton-polariton lasing and condensation in organic systems, photonic modes play a minor role at the emission frequency in our system, and this emission has an undefined momentum because of the structural imperfections. This remarkable result reveals the rich and distinct physics of strongly coupled organic molecules to photonic cavities.

Electrically driven optical metamaterials.

The advent of metamaterials more than 15 years ago has offered extraordinary new ways of manipulating electromagnetic waves. Yet, progress in this field has been unequal across the electromagnetic spectrum, especially when it comes to finding applications for such artificial media. Optical metamaterials, in particular, are less compatible with active functionalities than their counterparts developed at lower frequencies. One crucial roadblock in the path to devices is the fact that active optical metamaterials are so far controlled by light rather than electricity, preventing them from being integrated in larger electronic systems. Here we introduce electroluminescent metamaterials based on metal nano-inclusions hybridized with colloidal quantum dots. We show that each of these miniature blocks can be individually tuned to exhibit independent optoelectronic properties (both in terms of electrical characteristics, polarization, colour and brightness), illustrate their capabilities by weaving complex light-emitting surfaces and finally discuss their potential for displays and sensors.