Producing nanoscale laser spot for heat-assisted magnetic recording

Heat-assisted magnetic recording (HAMR) has the potential to keep increasing the areal density in next generation hard disc drives (HDDs) by producing a nanoscale laser spot using optical antenna, called 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 antenna provide the capability of sub-wavelength light focusing at optical frequencies. These antennas are designed using both plasmonic resonance and localized plasmons to produce an enhance 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 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, the design and characterization of these plasmonic antennas and the effect of optical properties on field localization, absorption, and coupling efficiency will be discussed. Computations of heat dissipation and the induced temperature rise in NFT are carried out to study their dependence on materials' properties. With the recent significant interests in searching for 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 NFT are investigated.