Influence of waveguide refractive index on near-field transducer efficiency in heat-assisted magnetic recordin

In a heat-assisted magnetic recording (HAMR) system, the optical recording head is one of the essential components, where light delivered from waveguide is focused into an optical spot in the scale of tens of nanometers to heat recording media to lower coercivity temporarily and locally by a near-field optical transducer. High transducer efficiency is desired for HAMR, as large energy lost during delivery can lead to heating of the recording head, component deformation and system failure at last. Up till now, most research interest has been paid to studying transducer to improve HAMR performance. However, besides the transducer itself, the waveguide also can influence transducer efficiency, because transducer interacts with the light guided in waveguide. In waveguide, propagation mode is determined by waveguide refractive index. In this paper, effects of refractive index of the waveguide core on transducer efficiency are studied by using finite-difference time domain (FDTD) simulation. With the knowledge of waveguide refractive index effects, Si waveguide is proposed to improve HAMR performance at near infrared wavelengths.