Splitting of Optical Spatial Modes via Stern-Gerlach Effect

Stern-Gerlach (SG) effect, initially found for unveiling the existence of quantized electron spins, is now a general concept describing a state-dependent separation. It is widely explored in optics to achieve a function of optical splitting, but the current schemes always require a polarization- or wavelength-dependent process, thus showing limitations for broader applications. Here, spatial modes of an optical field are employed as another degree of freedom to demonstrate an SG effect. Two modes of a pair of coupled waveguides are found to be in analog to the electron spins. They are able to undergo a splitting upon a spatially-dependent waveguide coupling, which plays the role of a non-uniform magnetic field. In an experiment, such a splitting is realized in two coupled non-parallel slab waveguides, and its strength is adjusted at ease by varying the parameters of this proposed structure. This SG-related optical splitting may find applications in the field of optical sensing and signal processing. Stern-Gerlach effect is widely explored in optics to achieve a function of optical splitting, but polarization- or wavelength-dependent dynamics have always been involved in past works. Here, spatial modes of an optical field are employed as another degree of freedom to demonstrate a Stern-Gerlach effect. The resulting optical splitting, independent of polarization/wavelength, is solely induced by a spatially-dependent optical coupling. image