Recent Advances in Near-Field-Based Small Form Factor Optical Storage

A review of small form factor optical storage (media diameters less than 50 mm) is presented with emphasis on the development of near-field technology. The current efforts are summarized together with the commercially desired attributes. The results of the examination of gallium phosphide (GaP) and diamond solid immersion lenses in conjunction with evanescent coupling are presented. A polarization-based gap error signal (GES) technique for air-gap servocontrol is described. Results indicate that the method is relatively insensitive to contamination on the surface and can resolve 100-nm surface features. A 50-GB 120-mm read-only memory (ROM) disc was successfully read and the results indicate that a 10-GB 32-mm diameter RW/ROM optical disc based on 650-nm lasers should be feasible