Near-field phase-change optical recording of 1.36 numerical aperture

A bit density of 125 nm was demonstrated through near-field phase-change (P C) optical recording at the wavelength of 657 nm by using a supersphere sol id immersion lens (SIL). The lens unit consists of a standard objective and a phi 2.5 mm SIL. Since this lens size still prevents the unit from being mounted on an air-bearing slider, we developed a one-axis positioning actua tor and an active capacitance servo for precise gap control to thoroughly i nvestigate near-field recording. An electrode was fabricated on the bottom of the SIL, and a capacitor was formed facing a disk material. This setup r ealized a stable air gap below 50 nm, and a new method of simulating modula tion transfer function (MTF) optimized the PC disk structure at this gap he ight. Obtained jitter of 8.8% and a clear eye-pattern prove that our system successfully attained the designed numerical-aperture (NA) of 1.36.