Passive all-optical isolator based on spatial self-phase modulation.

Optical isolators are essential devices that enable light propagation in a single direction, finding widespread applications in fields such as optical communication and optical computing. A prerequisite for these devices to achieve optical nonreciprocity (ONR) is the violation of Lorentz reciprocity. Traditional approaches to ONR rely on external magnetic fields, spatiotemporal modulation, or nonlinear optical effects.