Efficient Plasmonic Transducer for Nanoscale Optical Energy Transfer in Heat-Assisted Magnetic Recording

This paper presents a near-field plasmonic transducer that efficiently transforms a dielectric waveguide mode into a suitable plasmon mode for nanoscale optical energy transfer into a magnetic recording medium, for the application of heat-assisted magnetic recording (HAMR). The proposed transducer is a tapered hybrid plasmon-dielectric waveguide that typically consists of two hybrid plasmon modes. Along the taper, one of the hybrid modes approaches cutoff, while the other approaches the short-range surface plasmon mode that couples optical energy well into the recording medium over a nanospot size of 28 nm by 38 nm, owing to its relatively uniform and strong longitudinal field component. The power coupled into the SRSP mode, at the transducer input, is about 62% and this efficiency is preserved well along the length. This power in turn couples well into the recording medium with a maximum absorption efficiency of 7.87%. The absorption efficiency is relatively broadband. Even with the inclusion of a magnetic pole 30 nm away from the transducer, the maximum absorption efficiency is 6.44%. The proposed structure is tolerant to fabrication misalignments, since the metallic, gap and dielectric layers are all self-aligned. The high-efficiency, broadband nature and ease of fabrication, makes the proposed transducer highly suitable for HAMR applications, and possibly nanofocusing applications.