Optical, thermal, and bit-writing analysis of a directly coupled plasmonic waveguide for heat-assisted magnetic recording

Abstract

We investigate the energy conversion process and subsequent thermal and bit-writing performance of a plasmonic near-field transducer (NFT) under steady-state operation within heat-assisted magnetic recording (HAMR) devices. The NFT is composed of metal-insulator-metal (MIM) layers that are designed to localize heating and produce optimal thermal gradients in order to relieve parasitic heating effects in the NFT. The thin-film MIM structure confines the electromagnetic energy in the down-track direction while cross-track confinement is achieved by tapering the insulator feature of the MIM. A comparative analysis using Gold and a number of novel Au alloys is undertaken. Modeled performance shows excellent thermal spot confinement (50 × 50 nm2) of temperatures above 650 K at an input laser power of 830 nm of less than 5 milliwatts. In addition, micromagnetic simulations using a stochastic Landau-Lifshitz-Bloch equation yield excellent signal to noise ratio with minimum jitter of under 2 nm when recording.

Elliptical plasmonic near-field transducer and v-shape waveguide designs for heat assisted magnetic recording

“…For instance, in array-based nano-reactors for plasmonic photocatalysis, a thermal gradient of 1.9 K/nm is obtained [18]. In comparison, values as high as 15 K/nm have been reported for antenna-based plasmonic near-field transducers used in HAMR applications [19], the focus of this work.…”

“…This metric should be as large as possible since the largest increase in media temperature for the smallest increase in NFT temperature is desired to prevent the NFT from getting too hot; otherwise, the NFT could deform or melt, degrading its performance. The highest value for this metric was 8.60, obtained in a numerical study using an NFT of an alloy of Au 0.175 Ag 0.875 for a laser power of 4.9 mW [19], (ii) the thermal spot profile in the media at the full width at half maximum (FWHM) should maintain its 'squareness' to avoid having a long thermal tail in the media in both the cross-track and down-track directions, (iii) the thermal gradient in the media, which must be as large as possible, as having a sharp thermal gradient allows writing sharp transitions that are key to high linear densities, (iv) the normalised peak temperature, which measures the peak temperature in the media normalised by the total power incident on the NFT must also be as large as possible; it determines how much laser power is needed to deliver to excite the NFT and is also helpful for characterising the effects of laser intensity noise on the recording system [21], (v) and indeed the most problematic and central to all the aforementioned requirements is the reliability of the plasmonic near-field transducer itself, which is generally made of gold and must withstand the inevitable high temperature within the HAMR system.…”

Near-Field Generation and Control of Ultrafast, Multipartite Entanglement for Quantum Nanoplasmonic Networks

“…The schematic in Figure 4 a represents the effective open-cavity system used, which consists of light from surface plasmon polaritons (SPPs) produced by the NFT that is coupled to the QDs in separate media. 21 Given the effective cavity system, decay and especially dephasing rates are anticipated to vary. The decay rate includes enhancements to the spontaneous emission rate, that is, Purcell enhancement, expected to be on the order of 10 2 –10 3 depending on materials used.…”

“… 2 , 20 Optical energy efficiency, that is, percentage of input power delivered to the QD quantum emitters, is over 20%, thus comparable with similar state-of-the-art designs today. 21 We emphasize that the electric or magnetic field may be enhanced, thus opening up magnetic/spin transitions, as a crucial alternative to our archetype (see Supporting Information for details). 22 Importantly, the area of highest intensity is adjustable depending on input power and taper size at the air bearing surface and therefore capable of entangling multiple qubits simultaneously.…”

“…This is compared to other, more narrowly tapered resonator/probe designs such as those used in atomic force microscopy. 21 We build on the recent demonstration that NFTs are valid sources of subdiffracted, near-field light-generating sufficient field strengths incident on the QD media, as shown in Figure 1 c,d, for near-field strong coupling, single-photon emission, enhancement of spontaneous emission, and bipartite entanglement. 23 , 24 We now verify via theoretical simulation the ability to dynamically control multipartite entanglement on a picosecond scale while achieving excellent fidelity of the state we wish to excite.…”