Deep subwavelength flow-resonant modes in a waveguide-coupled plasmonic nanocavity

The waveguide-coupled plasmonic nanocavity is known to be a deep subwavelength platform that combines on-chip compatibility with a strong light-matter interaction at the resonance of local field enhancement; however, the resonant local field enhancement provides no magneto-optical activity. We conceptually investigate the deep subwavelength flow-resonant modes of the waveguide-coupled plasmonic nanocavity at which the local field enhancement deviates from the strongest and, instead, the power flow reaches its maximum. These flow-resonant modes exhibit resonant enhancements of magneto-optical activity and the inverse Faraday effect. Frequency-selective enhancement of light-magnetization interaction at the flow-resonant modes allows us to propose multichannel all-optical writing and reading of magnetic bits in nanophotonic integrated circuits. Our findings would open the way towards on-chip deep subwavelength magneto-optical devices and opto-magnetic recording with a great potential for high-speed on-chip memory.