Subwavelength cavities via hyperbolic dispersion in two dimensional hybrid perovskites

Two dimensional hybrid organic inorganic perovskites offer great promise in applications concerning light matter interactions due to their large oscillator strength, high binding energy and electrical isolation of the inorganic halide layers surrounded by organic cations. Recently, it was shown that the N=1,2 members of this perovskite family exhibit excitonic anisotropy in the in-plane and out of plane orientations of the crystal axis. Such anisotropic permittivity tensor naturally gives rise to a type II hyperbolic dispersion (e_xx=e_yy<0 and e_zz>0) in the visible frequency range. Here, we show the possibility of realizing subwavelength cavities using these perovskites owing to their hyperbolic dispersion. These cavities show strong field confinement with a Purcell enhancement of 11. Furthermore, they show dimension free scaling of resonant frequency, a hallmark of hyperbolic cavities. By calculating the imaginary part of Green’s function, we numerically show that such cavities exhibit large local density of photonic states. We map the isofrequency surface for in-plane and out of plane momenta by calculating the Fourier transform of the spatial fields confined in these cavities.