KEYWORDS: Resonators, Magnetism, Temperature distribution, Electric fields, Dielectrics, Nanoantennas, Cladding, Near field, Heatsinks, Quantum simulation
Heat-assisted magnetic recording (HAMR) is a promising technology to increase the recording density of hard disk drives. A near-field transducer (NFT), which forms a small light spot on the recording medium, is necessary in HAMR. We previously proposed a device for a HAMR heat source, in which a metal nano-antenna as an NFT is attached to a semiconductor ring resonator as a light source via a dielectric spacer. We have been analyzing the temperature rise using this device including the recording medium through the combination of optical and thermal simulations. The objective of this study is to decrease the nano-antenna temperature by optimizing its structure. Two types of devices (Types 1 and 2) were newly proposed. In Types 1 and 2, a small hole and a narrow groove, which was filled with a dielectric material, was respectively formed on the side of the ring resonator, and the nano-antenna was partially embedded into it. The metal for the nano-antenna was Au, and the dielectric for the spacer, hole, and groove was SiO2. When the peak temperature of the recording layer was around 800K (slightly higher than the Curie temperature), the nano-antenna temperature was around 560K for the conventional device, but it could be decreased to around 360 to 380K for the proposed devices. This is a sufficiently low value to keep the hardness of nano-antenna. On the other hand, the thermal spot size in the recording layer for the proposed devices was slightly larger than that for the conventional device.
Heat-assisted magnetic recording (HAMR) is a promising technology to increase the recording density of hard disk drives. A near-field transducer (NFT), which forms a small light spot on the recording medium, is necessary in HAMR. We previously proposed a device for HAMR, in which a metal nano-antenna as an NFT is attached to a semiconductor ring resonator as a light source. There are even and odd modes in this device. Because the near-field light is generated at the nano-antenna tip only in the even mode, how to excite the even mode selectively is an important issue. For this purpose, we introduced a split-ring-resonator-type device and investigated its effectiveness through a numerical simulation considering gain. When a narrow gap was placed at the nano-antenna bottom (Type 1) or at the opposite side to the nano-antenna bottom (Type 2) in the ring resonator, the gain for the even mode became higher than that for the odd mode. When the gap width increased, the gain difference became maximum at a certain width and then gradually decreased. The energy density at the nano-antenna tip for Type 1 was higher than that for Type 2. As the gap width increased, the energy density for Type 1 increased. Moreover, in Type 1, when the nano-antenna position was varied from outside to inside the ring resonator, the gain difference gradually decreased and the energy density increased. Therefore, the gap width and nano-antenna position should be designed considering the trade-off relationship between the gain difference and energy density.
Heat-assisted magnetic recording (HAMR) is a promising technology to increase the recording density of hard disk drives to more than 10 Tb/inch2. In HAMR, a near-field transducer (NFT) is necessary to form a light spot with the order of 10 nm to heat the recording medium locally to reduce its coercivity during recording. The authors’ group has proposed a device for HAMR, in which a metal nano-antenna acting as an NFT is attached to a semiconductor ring resonator acting as a light source. Because the characteristics of near-field light are influenced by the material and structure of nano-antenna, we investigated a metal-dielectric hybrid nano-antenna in this study. Especially, a core-shell-type nano-antenna, in which a dielectric sphere as a core was embedded in a gold tip as a shell, was taken as an example, and how the core refractive index and core radius influence the energy density and spot size of near-field light was numerically simulated. The tip radius of nano-antenna was 25 nm. As a result, when the core radius was 20 nm, maximum energy density of about 25 times and minimum spot size of about 91% compared with conventional gold-only nano-antenna were obtained at the core refractive index of 4.4 and 4.8, respectively. As the core refractive index became higher, the optimum core radius became smaller. Moreover, the behavior of energy density could be understood by one-sphere model and that of spot size could be understood by two-sphere model, both of which are determined by the localized surface plasmons.
Heat-assisted magnetic recording (HAMR) is a promising technology for achieving more than 10 Tb/inch2 recording density. A near-field transducer (NFT), which forms a small light spot on a recording medium, is necessary in HAMR. The authors’ group has proposed a novel device, in which a metal nano-antenna as an NFT is attached to a semiconductor ring resonator as a light source. There are multiple eigenmodes in this device. If they are excited simultaneously, the device becomes unstable because of the mode competition. Moreover, a near-field light is generated at the tip of nano-antenna for some eigenmodes but not generated for other eigenmodes. Therefore, in this study, how to excite a desired eigenmode selectively among the multiple eigenmodes was investigated through a numerical simulation. The eigenmodes were classified into four types: modes in the radial direction (characterized by the order of mode l), modes in the tangential direction (characterized by the order of mode m), even and odd modes, and TE and TM modes. The mode with l = 1 could be excited by increasing the inner diameter of the ring resonator. The mode with specific m and the even mode could be excited by forming the slits in the ring resonator and using the frequency dependence of gain. The TE mode could be excited automatically because of its strong light confinement in the active layer. By combining these methods, the device could be made stable and the near-field light could be generated at the tip of nanoantenna.
Heat-assisted magnetic recording (HAMR) is a promising technology for achieving more than 10 Tbit/inch2 recording density. A near-field transducer (NFT), which forms a small light spot on a recording medium, is necessary in HAMR. However, the heat generated by the NFT would melt the NFT itself. To solve this problem, the authors have proposed a novel device, in which a metal nano-antenna is attached to a semiconductor ring resonator. In this paper, the near-field light generated by the semiconductor ring resonator with the metal nano-antenna was analyzed through a numerical simulation to optimize the structure of the device. The simulation was conducted using the finite element method based on a 3-dimensional model. It was found that how to excite a desired eigenmode selectively among some eigenmodes is important to make the device effective, and that various design parameters such as the length of the nano-antenna and the distance between the ring resonator and the nano-antenna can be optimized.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.