Finite-difference-time-domain analysis for electro-magnetic field distribution on near-field optical recording probe head

In recent years there has been a strong trend and movement towards digitalism and high memory capacity in the multi-media field including digital movies. It is expected that new kinds of high density data storage to match this environment will be developed. The optical disk system using near-field optics and technology is considered to be a strong candidate for ultra-high density optical memory. In order to realize a new optical recording system we have focused on the writing head with high optical efficiency and resolution. We evaluated the properties of pyramidal probe heads using the FDTD (finite difference time domain) method and obtained simulation results in order to find the best structure and design for new near-field optical probes. From these results, we understood that a novel probe structure having metal layers on just 3 side planes (scoop type) shows the best performance in optical power density and beam size. We believe that optical enhancement and beam confinement arise from the effect of surface plasmon on a metal layer and the beam blocking of metal, respectively. Using this scoop-type probe having a tip size of 55 nm, we can get a very small spot size of 33 × 60 nm² in FWHM (full with half maximum), which allows us to realize the recording density of 300 Gb/in².