Hybridized polaritons are generated by simultaneously coupling two vibrational modes of two different organic materials to the resonance of a low-loss infrared optical microcavity. A thin film of poly methyl methacrylate with solvent molecules of dimethylformamide trapped inside provided two spectrally narrow, closely spaced carbonyl stretches with absorption peaks at 1731 and 1678 cm(-1). Situating this film in a microcavity based on Ge/ZnS distributed Bragg reflector mirrors produced three distinct polariton branches in the dispersion relation due to hybridization of the vibrational resonances. Two anticrossings were observed with Rabi splittings of 9.6 and 5.2 meV, between the upper-to-middle and middle-to-lower polariton branches, respectively. This system marks the first demonstration of polariton hybridization between a solid and solvent molecules and can open new paths toward chemical reaction modification and energy transfer studies in the mid-infrared spectral range.

Perovskites are currently attracting extensive research interest as a wavelength-tunable lasing material. As a first step toward electrically pumped lasers, numerous investigations have recently reported amplified spontaneous emission (ASE) of optically pumped perovskites with remarkably low thresholds. Here, we investigate the optical aspects of perovskite ASE, to establish the design principle of materials and devices. We show that compared to solution-processed CsPbBr3, vacuum deposition yields superior ASE characteristics with a threshold of 35 μJ/cm2. The optical loss (R loss) during lateral photon propagation in the waveguide mode is identified as a key parameter to determine the ASE quality. With spatially resolved photoluminescence, we determine R loss as 40 and >1000 cm–1 for vacuum and solution-processed perovskites, respectively. We present a comprehensive model that relates ASE, gain length, optical loss, temperature, and density of states. Finally, we succeed in demonstrating ASE in perovskite samples with metal electrodes, mimicking a diode architecture for electrical pumping. Optical spacer layers are shown to play a crucial role in preventing metal absorption loss in waveguide modes.

An open microcavity (OMC) is an optical system that is composed of two mirrors, where one is fixed and the second is on a movable stage. OMCs enable tuning the optical resonances of the system and insertion of different materials between the mirrors and are therefore of large scientific interest due to their many potential applications. Strong light–matter coupling of the vibrational transitions of organic molecules with the optical modes of a microcavity generates new polaritonic states in the mid-infrared (mid-IR) spectral region. Here we achieve strong light–matter coupling in the mid-IR using a low optical-loss OMC that is wavelength-tunable via a piezoelectric actuator. A thin film of poly­(methyl methacrylate) (PMMA) was deposited onto one of the mirrors to couple the narrow and intense absorption peak of the carbonyl stretch mode at 1731 cm–1 to the OMC. Polaritonic states are observed in FTIR transmission measurements when an OMC resonance is matched to the carbonyl stretch. By dynamically varying the cavity photon mode around the resonance condition, we determine the normal mode polariton dispersion relation and obtain a maximum Rabi-splitting ℏΩR = 7.0 ± 0.18 meV. Different cavity line widths and Rabi-splittings can be achieved by changing the mirror separation, thus providing control of the coupling strength relative to dephasing. The ability to insert multiple materials inside an OMC and generate strong light–matter coupling over a large range of wavelengths can open new paths toward chemical reaction modification and energy transfer studies in the mid-IR.

We demonstrate an unexpected tenfold reduction in the lasing threshold of an organic vertical microcavity under subpicosecond optical excitation. In contrast to conventional theory of lasing, we find that the lasing threshold depends on the rate at which excitons are created rather than the total energy delivered within the exciton lifetime. The threshold reduction is discussed in the context of microcavity-enhanced super-radiant coupling between the excitons. The interpretation of super-radiance is supported by the temporal relaxation dynamics of the microcavity emission, which follows the super-radiance time rather than the cavity lifetime. This demonstration suggests that room-temperature super-radiant effects could generally lower the threshold in four-level lasing systems of similar relaxation dynamics.

Topological interface states are formed when two photonic crystals with overlapping band gaps are brought into contact. In this work, we show a planar binary structure with such an interface state in the visible spectral region. Furthermore, we incorporate a thin layer of an active organic material into the structure, providing gain under optical excitation. We observe a transition from fluorescence to lasing under sufficiently strong pump energy density. These results are the first realization of a planar topological laser, based on a topological interface state instead of a cavity like most of other laser devices. We show that the topological nature of the resonance leads to a so-called “topological protection”, i.e. stability against layer thickness variations as long as inversion symmetry is preserved: even for large changes in thickness of layers next to the interface, the resonant state remains relatively stable, enabling design flexibility superior to conventional planar microcavity devices.