Abstract
By variation of a refractive index and aspect ratio of the isolated disk, we achieved exceptional points (EPs) at which the resonant frequencies and resonant modes coalesce. However, in practice, that kind of variation presents a technological problem. We considered the method to avoid the problem by substitution of two disk’s dimers. In each dimer, variation of the distance between disks was equivalent to a variation of the aspect ratio of the dimer. Moreover, the variation of the distance between dimers provides the second parameter that gives rise to a vast number of EPs. We recovered the initial resonant eigenmode by encircling multiple EPs two, three, and four times in the two-dimensional parametric space of distances.
Highlights
A dielectric particle embedded into open space is specified by eigenfrequencies, which are complex owing to open boundary conditions for the solutions of the homogeneous Maxwell equations
Many works on exceptional points (EPs) and their applications are associated with parity-time (PT) symmetric optical systems with a balanced gain and loss
The examples of the evolution of the complex eigenfrequencies are presented in Figure 3 centered around resonances of the isolated disk shown by closed red circles and corresponding resonant modes in the insets
Summary
A dielectric particle embedded into open space is specified by eigenfrequencies, which are complex owing to open boundary conditions for the solutions of the homogeneous Maxwell equations. The appearance of EPs can be exploited to a broad range of interesting applications, including lasing [9], asymmetric mode switching [10], nonreciprocal light transmission [11,12], and ultrasensitive sensing [13]. The first scale introduced a coupling strength between disks in a dimer, and the second scale introduced a coupling strength between distant dimers This approach made it easy to conduct experimentally two-fold variation in order to achieve EP as it was exploited first for experimental evidence of EPs in a system of three and more paired gold nanobars moving relative to each other [32]. The appearance of EPs can be exploited to a broad range of interesting applications, including lasing [9], asymmetric mode switching [10], nonreciprocal light transmission [11,12], enhancement of the spontaneous emission [35], and ultrasensitive sensing [13]
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