Optical and Thermal Behaviors of Plasmonic Bowtie Aperture and Its NSOM Characterization for Heat-Assisted Magnetic Recording

Abstract

Heat-assisted magnetic recording has the potential to keep increasing the areal density in the next-generation hard disk drives using a nanoscale optical antenna, called a near-field transducer (NFT), to locally and temporally heat a sub-diffraction-limited region in the recording medium. The NFTs made of plasmonic nanoscale optical antennas provide the capability of sub-wavelength light manipulation at optical frequencies. These antennas are designed using both plasmonic resonance and localized plasmons to produce an enhanced field in an area far below the diffraction limit. To reduce the self-heating effect in the NFT, which could cause materials failure that leads to the degradation of the overall hard drive performance, the NFT must deliver sufficient power to the recording medium with as small as possible incident laser power. In this paper, using the bowtie aperture as an example, we present the effect of optical properties on field localization, absorption, and coupling efficiency. Computations of heat dissipation and the induced temperature rise in the NFT are carried out to study their dependence on materials’ properties. With the recent significant interests in alternative low-loss plasmonic materials in the visible and near-infrared range, the possibility of using alternative plasmonic materials for delivering higher power and simultaneously reducing heating in the NFT is investigated. The NFT characterization using scanning near-field scanning optical microscopy is also discussed.