Modeling of Polarization Effects in Au Nanodots Excited With InAs Quantum Dot Emitters for Use as a HAMR Heat Source

We present modeling of a novel device structure with possible application as a heat assisted magnetic recording source. The structure consists of a mesa of GaAs containing InAs quantum dots (QD's), on a GaAs substrate. An Au dot atop the MESA is in proximity to a HAMR medium. The Au dot acts as a resonant absorber of the QD emission and also provides coupling between the optical transducer and recording medium. The device is illuminated through the substrate, with light that is absorbed by the QD's and re-emitted at a longer wavelength, characteristic of the dots. For varied polarization of the QD light emission, finite element modeling was used to compute the electromagnetic field structure of the device, along with the resultant temperature field in the recording medium and the device. We show that certain polarization emission are preferable for attaining more intense excitation of resonance in the Au dot atop the mesa. Temperature ratios (medium versus the Au dots) greater than 60 times were seen, due to the good heat sinking of the Au dot provided by the GaAs mesa and substrate. Coupling efficiencies between the device and medium were low, with typically less than 0.3% of the power emitted by all radiators coupling into the full-width half-maximum of the medium hot spot. While improvements may be possible, even at low efficiency this device shows promise in keeping the near field transducer cool relative to the medium.