Near-Field Optical Recording/Readout Using a 405nm Wavelength GaN Laser Diode

Abstract

Near-field recording/readout using a solid immersion lens (SIL) is capable of achieving a numerical aperture (NA) of greater than unity and a higher storage density than conventional optical disc systems. In near-field recording using a SIL, a material having a higher refractive index results in a smaller spot size, as does using a shorter wavelength light source. However, the conventionally used GaN 405-nm laser diode (LD) still has several advantages over shorter wavelength light sources; for example, it can achieve a higher recording density and it is possible to produce more reliable near-field recording/readout systems based on it. We describe a trial that seeks to achieve a higher data transfer rate using a 1.84-NA dual-channel near-field recording/readout system that employs a monolithic dual-beam blue LD.