Cavity optomagnonics with magnetic textures: Coupling a magnetic vortex to light

Optomagnonic systems, where light couples coherently to collective excitations in magnetically ordered solids, are currently of high interest due to their potential for quantum information processing platforms at the nanoscale. Efforts so far, both at the experimental and theoretical level, have focused on systems with a homogeneous magnetic background. A unique feature in optomagnonics is, however, the possibility of coupling light to spin excitations on top of magnetic textures. We propose a cavity-optomagnonic system with a nonhomogeneous magnetic ground state, namely, a vortex in a magnetic microdisk. In particular, we study the coupling between optical whispering gallery modes to magnon modes localized at the vortex. We show that the optomagnonic coupling has a rich spatial structure and that it can be tuned by an externally applied magnetic field. Our results predict cooperativities at maximum photon density of the order of C approximate to 10(-2) by proper engineering of these structures.