Because they produce small spot size, near-field techniques are applied to optical data storage systems to increase recording density. Two practical near-field implementations are aperture probes and solid immersion lenses (SILs). The basic signal modulation 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. © 2001 Society of Photo-Optical Instrumentation Engineers.