Publication date: 22nd July 2026
Two-dimensional (2D) metal halide perovskites are emerging materials with bright and tunable emission that are highly attractive for photonics. Their hybrid organic-inorganic structure provides ample opportunities to tailor their optical properties and radiative recombination dynamics.[1, 2] Strong dielectric confinement results in high exciton binding energies, and their high refractive index favors strong-light matter interaction.[3, 4] In particular, highly homogeneous slabs of 2D perovskites can act themselves as optical cavities and lead to self-hybridization of the photonic cavity modes with the band edge exciton levels. The strong non-linearity of the complex refractive index inside the self-sustained cavity leads to low group velocity of the light and an abnormal dispersion near the band edge that results in high damping and leaky optical modes.
We investigate the reflectance and photoluminescence of single 2D lead iodide microcrystals that act as highly efficient optical cavities. We observe an extremely large number of cavity modes in microcrystals with micrometer thickness. This allowed us to determine the complex refractive index using the interference fringes method combined with a Cauchy dispersion for the transparent low energy range of the cavity mode spectrum. We then use the obtained dispersion of the refractive index in the calculation of the exciton-polariton anticrossing based on a Lorentz oscillator model, and by fitting the experimentally obtained reflectance minima near the band gap we obtain the salient optical parameters of the emitter material. We further observe additional mode splitting that will be discussed in terms of exciton-phonon coupling.
Our experiments show that 2D perovskite microcrystals with highly regular shape and homogeneous thickness constitute a versatile platform for integrated and non-linear photonics
References
[1] R. Krahne, et al., Nano Lett., 24, 11124-11131 (2024).
[2] R. Krahne, et al., Acc. Chem. Res., 57, 2476-2489 (2024).
[3] M. Borreani, et al., Adv. Opt. Mater., 13, e01276 (2025).
[4] A. Schleusener, et al., Adv. Mater., 36, 2402924 (2024).
The work work funded by the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Funding Program (Project Together, grant agreement No.101067869), and under Project 101131111 – DELIGHT.
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