New solid immersion lenses (SILs) have been studied for a high-density optical storage system by the near-field process that can overcome the far-field diffraction limit. We have proposed the aspherical SILs, named elliptic SIL (ESIL) and Cartesian SIL (CSIL) according to geometrical optics. The SILs have a high numerical aperture (NA), for instance, the NAs of the ESIL and the CSIL are over 1, with a refractive index of 1.56 of the disc cover layer. The SILs that include the function of the objective lens are able to read/write the signals inside the disc substrate. The optical heads employing an internal recording method are expected to be utilized in an unsealed environment. Experimental results of the application of an ESIL are presented. The replicated ESIL (RESIL) has been proposed to solve critical issues such as the problems of the thickness error of the SILs or the disc substrate. The problems need to be solved for the commercialization of the near field recording (NFR) technology.
All Science Journal Classification (ASJC) codes
- Physics and Astronomy(all)