Highly Chiral Exceptional Point in Coupled Resonators Perturbed by Nanoscatterers

With employing strong chirality in an optical system, the direction of light propagation can be controlled and subwavelengh particles can be detected. Here, we show that different kind of chiral Exceptional Point (EP) with high (spatial) chirality, can appear in a coupled resonator perturbed by nanoscatterers, in which both of distance and position of the scatterers can be tuned. We achieve strong chiral EP in two different distances between the resonators, with chirality around 0.99, in the both cases. Besides, chiral EP associated to the higher harmonic whispering gallery mode (WGM) is achieved, with chirality around 0.95. We also investigate interaction of particles with same and different spin of light, which can mimic the spin-up and spin-down of electrons in quantum mechanics. The proposed device provides a tunable scheme to achieve high directionality of different cavity modes by incorporating one or more nanoscatteres. With incorporating more than one tunable mechanisms such as nanoscatterers, nonlinearity, and time-moulation, simultaneously, the conventional limitations in chirality and sensitivity may be surpassed, in the presence of unwanted imperfections of fabrication and noisy environment.