Aberration compensation in near-field optics for multilayer data storage

Spherical aberration (SA) is induced by a change in the focused layer in a multilayer system. In a multilayer far-field system, any kind of aberration-generating system can well compensate the SA induced by a change in the focused layer. However, the method used in the multilayer far-field system cannot be applied to a multilayer near-field recording (NFR) system with a solid immersion lens (SIL), because of many critical reasons including sensitivity. In a multilayer NFR SIL system, another method is required to compensate aberration. The use of a liquid crystal plate (LCP), afocal telescope-type lens compensator or a compact combined lens system is considered for the compensation of SA in the multilayer NFR SIL system in this study.