Simulation of a Thermally Efficient Heat-Assisted Magnetic Recording Ridge Waveguide NFT on an AlN Heat Sink

A thermally efficient ridge waveguide near-field transducer (NFT) design on an AlN heat sink is presented. Through simulation, we found our design can achieve thermal efficiency (TE), defined as the ratio of peak temperature rise in the medium to that in the NFT as high as 2.93. The ridge waveguide NFT is placed on a heat sink of high thermal conductivity material AlN, while otherwise surrounded by SiO
₂
as the top cladding and cavity filling material. The relatively large metallic waveguide structure can dissipate heat effectively even in the presence of finite interface thermal conductance between the NFT and the AlN. Different NFT excitation methods are examined, with an impinging dielectric waveguide mode leading to the highest TE. Some challenges are identified in using excitation by resonant disk structures. We note that surface plasmon is confined inside the NFT cavity, while heat escapes through the outer surface of the NFT, separating the dielectric interfaces responsible for optical propagation and heat transfer. This allows for further reduction in thermal interface resistance by adding an interface adhesion layer like Cr at the NFT/AlN interface without sacrificing optical properties.