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Heat-assisted magnetic recording (HAMR) is a promising technology for improving the recording density of hard disk drives. A near-field transducer (NFT), which forms a small light spot on a recording medium, is necessary in HAMR. The authors' group previously proposed a device, in which a metal nano-antenna acting as an NFT is attached to a semiconductor ring resonator acting as a laser. There are TE- and TM-like modes in the ring resonator. Because a near-field light is generated at the tip of nano-antenna only in TE-like mode, how to excite TE-like mode selectively is an important issue. In this study, a numerical simulation considering gain was conducted to investigate whether a double-ring-resonator-type device is effective for improving the mode selectivity between TE- and TM-like modes. The size of the ring resonators was determined so that the resonance frequency of each ring resonator was almost the same for TE-like mode and slightly different for TM-like mode. The double-ring-resonator-type device was found to be effective for making the laser oscillation with TE-like mode more dominant than with TM-like mode. The size of the smaller ring resonator should not be too small to secure practical manufacturing tolerance. Moreover, both ring resonators should have gain to obtain adequate gain for each mode and energy density at the tip of nano-antenna simultaneously. [ABSTRACT FROM AUTHOR]

Heat-assisted magnetic recording is a technology to improve recording density for hard disks. The authors' group has proposed a device, in which a gold nano-antenna as a near-field transducer is attached to a semiconductor ring resonator as an integrated light source. Localized surface plasmon resonance at the tip of nano-antenna excites near-field light to form small recorded marks to increase recording density. In this study, to improve the device performance, the dependence of spot size and energy density of near-field light on tip curvature, length, and bottom diameter of nano-antenna was investigated through a numerical simulation. Cylinder type and cone type nano-antennas were considered. For both types, as the tip curvature of nano-antenna increased, the spot size decreased and the energy density increased. It was possible to reduce the spot size to 18 × 18 nm2. For cylinder type, there was an optimal length of nano-antenna where the energy density became maximum, and the optimal length changed depending on the presence or absence of recording medium. This was because of the difference in plasmon resonance condition. Moreover, for cone type, there was an optimal bottom diameter of nano-antenna where the energy density became maximum, and the optimal bottom diameter changed depending on the length of nano-antenna. [ABSTRACT FROM AUTHOR]

Heat-assisted magnetic recording (HAMR) is a promising technology with high recording density. The authors' group has proposed a novel device for HAMR, in which a metal nano-antenna as a near-field transducer is attached to a semiconductor ring resonator as a light source. The ring resonator oscillation should be stable to generate steady near-field light with proper energy density to heat the recording medium. To improve the device performance, the dependence of resonance frequency, electric field intensity distribution, and normalized energy density at the tip of the nano-antenna on ring width and ring size was numerically simulated. When the ring width became wider, the resonance frequency and normalized energy density were more stable and operable, which leads to wide manufacturing tolerance. Although unnecessary solutions with higher radial mode order appeared in this condition, they are easy to control. When the ring size became smaller, the frequency interval between adjacent modes became wider, which leads to the stability of laser oscillation. Moreover, the normalized energy density was increased. As a result, the ring resonator obtains its optimal result with a wide width and an adequately small size. [ABSTRACT FROM AUTHOR]