An optical equilibrium in lateral waveguide-resonator optical force

We consider the lateral optical force between resonator and waveguide, and study the possibility of an equilibrium that occurs solely from the optical force. We prove analytically that a single- resonance system cannot give such an equilibrium in resonator-waveguide force. We then show that two-resonance systems can provide such an equilibrium. We provide an intuitive way to predict the existence of an equilibrium, and give numerical examples.