Resonant light-matter interaction between a molecular transition and a confined electromagnetic field can result in strong coupling where a coherent exchange of energy between light and matter occurs to form a new set of particles called polaritons. Being hybrid particles, polaritons exhibit a wide variety of quantum phenomena such as Bose-Einstein condensation, superfluidity, quantum phase transitions and many others. Recent progress in fundamental understanding and technological advancement in the field of polariton physics has allowed scientists to design and develop many impressive experimental configurations to obtain new insights into the strong interaction of light and matter in different material systems. Among all polariton configurations, microcavity polaritons based on organic materials have been emerging as a promising platform to easily achieve strong light-matter coupling at ambient conditions due to their unique properties compared to the conventional inorganic polariton systems. This mini review covers design principles and typical configurations of organic microcavity polaritons with a short tutorial on essential conditions to be satisfied for the strong coupling regime.
Room‐temperature interaction between light–matter hybrid particles such as exciton–polaritons under extremely low‐pump plays a crucial role in future coherent quantum light sources. However, the practical and scalable realization of coherent quantum light sources operating under low‐pump remains a challenge because of the insufficient polariton interaction strength. Here, at room temperature, a very large polariton interaction strength is demonstrated, g ≈ 128 ± 21 µeV µm2 realized in a 2D nanolayered metal–organic framework (MOF). As a result, a polariton lasing at an extremely low pump fluence of P1 ≈ 0.01 ± 0.0015 µJ cm−2 (first threshold) is observed. Interestingly, as pump fluence increases to P2 ≈ 0.031 ± 0.003 µJ cm−2 (second threshold), a spontaneous transition to a polariton breakdown region occurs, which has not been reported before. Finally, an ordinary photon lasing occurs at P3 ≈ 0.11 ± 0.077 µJ cm−2 (third threshold), or above. These experiments and the theoretical model reveal new insights into the transition mechanisms characterized by three distinct optical regions. This work introduces MOF as a new type of quantum material, with naturally formed polariton cavities, that is a cost‐effective and scalable solution to build microscale coherent quantum light sources and polaritonic devices.
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