Towards $\mathcal{PT}$-symmetric optical dimer fabrication without a light-absorbing material

We consider an approach to engineer an optical dimer of particles operating in the spectral region near the dipolar resonance that exhibits parity–time symmetry-like features. Both particles are assumed to be made of a gain medium with the same refractive index and extinction coefficient. We suggest introducing a gain–loss contrast by altering the radiative loss of the particles through changing their shape. To demonstrate our approach, we consider a dimer of infinite filled and hollow cylinders. We demonstrate that a larger hollow diameter leads to a stronger radiative decay. Then we find the parameters of a dimer that has an exceptional point at a real frequency and exhibits two real eigenfrequencies when the gain–loss contrast is decreased.