The influence of media optical properties on the efficiency of optical power delivery for heat assisted magnetic recording

We report simulation of optical power delivery for heat assisted magnetic recording that examines the effect of the medium optical properties. Power is delivered to the medium using a near field transducer (NFT), creating a hot spot with a full width at half maximum of 50 nm. Efficiency is computed as the ratio of power dissipated in the medium within the full width at half maximum of the spot to the reference power level incident on the NFT. This efficiency was computed for a range of real and imaginary indices of refraction ( n and k , respectively) of the medium ranging from 0 to 5 at a free space wavelength of 828 nm. The results indicate a maximum coupling of 4% of the power within the hot spot for the relatively low n and k values of 1.2 and 0.6, respectively. A simple model of termination impedance is used to explain these n and k values.