Because they produce small spot size, near-field techniques are applied to optical data storage systems in order to increase recording density. For data storage, the optical near field is defined in terms of evanescent coupling between the system used to read data and the recording layer. Two practical implementations that use evanescent energy are aperture probes and solid immersion lenses (SILs). In this paper, the basic characteristics of these systems are reviewed, and some considerations for improving performance are discussed. Combinations of SILs and apertures could produce data storage systems with ultra-fine resolution and good detection characteristics.
Tomas D. Milster, Tomas D. Milster,
"Near-field optical data storage: avenues for improved performance", Proc. SPIE 4081, Optical Storage and Optical Information Processing, (6 July 2000); doi: 10.1117/12.390497; https://doi.org/10.1117/12.390497