Heat-assisted magnetic recording (HAMR) demonstration using C-shaped nano-apertures

Abstract

Heat assisted magnetic recording (HAMR) is a next generation technology proposed for achieving magnetic storage densities beyond 1 Tb/in 2 . However, the commercialization of heat-assisted magnetic recording faces substantial technical challenges that must be resolved before widespread adoption of the technology can commence. Foremost of these challenges is the development of a precise method of delivering light to a very small, sub wavelength bit area with sufficient power to heat a high coercivity magnetic medium above its Curie temperature. Complex fabrication processes, low power transfer efficiency and high heat dissipation are the biggest problems faced in current HAMR light delivery systems. A nano-aperture vertical cavity surface emitting laser (VCSEL) is a potential candidate as a light delivery system in HAMR. We have fabricated 850 nm VCSELs with C-shaped nano-apertures on their output facets to be used as near-field transducers in order to produce a small localized optical spot; we then characterized their performance and compared power requirements with successful HAMR demonstrations with control C-shaped nano-aperture near-field transducers fabricated on glass substrates. Laser light at 850 nm wavelength was focused onto a magnetic medium, through the nano-apertures, and an external magnetic field of magnitude much lower than the coercivity (at room temperature) of the magnetic medium was simultaneously applied. Magnetic force microscopy images of the medium showed that C-apertures are capable of producing a magnetic spot much smaller than the diffraction limit using localized plasmonic effects. The power density required at this wavelength for HAMR process was experimentally measured using a pump-probe optical setup.