Nanofocusing probe limitations for a ultra-high density optical memory

Abstract

The limitation aspects of nanofocusing recording probes are discussed in this paper. The definitions of nanophotonics and nanofocusing are underlined. In this nano-age optical nanophenomena are described for nanometric architectures and nanostructural photonic devices. The nanofocusing probe limitations are connected with the wave-optics diffraction limit, geometrical beam tiny focusing, electromagnetic wave design, fabrication errors, nanoprobe energetic efficiency, near-field air gap and optical disk surface conditions. The micro-structure of the designed near-field optical head is discussed. The obtained nanofocused spot size is about 20 nm for the near-field space. The computed finite differential time domain (FDTD) power density spot is under 200 nm without any optical optimization. The far-field functions have a diffraction limit of 150 nm. The energy intensity can be elevated by more than 70 times in the FDTD calculated focal point using a convex microlens (ML) surface for focusing of a 8 µm vertical-cavity surface-emitting laser (VCSEL) beam. The optical power density is compressed up to 1024 times to the exact nanofocused spot in comparison with the entrance VCSEL micro-beam. The experimentally fabricated ML arrays and single lenses are presented. The optical quality and ML radius control with an AFM method is fulfilled. The optical integration technology for the proposed nanofocusing probe fabrication is announced. The nanofocusing probe spots are 10–13 nm for the central zone of the ML surface. The merit spot sizes are 10–18 nm for the entire ML nanofocusing diameter. For a single ML nanofocusing near-field head the energy spots have sizes from 9 to 15 nm, limited by technological aberrations.

Electron-Beam Detection of Bits Reversibly Recorded on Epitaxial InSe/GaSe/Si Phase-Change Diodes

“…These measurements will indicate the maximum practical storage density for electron-beam recording on phase-change media. The InSe/GaSe/Si medium should also be considered for use in ultra-high density optical memories 4,5,9) with an optical write, electrical read-back scheme.…”

“…1) A recent typical digital versatile disc (DVD) prototype system with a 405 nm light source employed an amorphous bit length of 126.9 nm with a land/groove width of 340 nm. 2) Advanced recording schemes that propose to drive bit sizes even smaller have incorporated the near-field scanning optical microscope, 3) nanofocusing probes 4) and solid-immersion lens 5) technologies. Several other groups have proposed using microfabricated arrays of scanned probes to record onto phase-change materials similar to those used as commercial optical recording media.…”

Simulation and experimental verification of nanoscale motion in a 2-axis quasi-passive platform

“…For example, in fiber telecommunication, optical alignment requirements are approaching the nanometer level due to the continuous increasing need for communication bandwidth [1]. In micro- [2] or nano-optics [3], positioning of micro optical components and nanodevices in nanometer scale is very demanding. In biology, manipulation and characterization of single cells are important for genomics and proteomics [4].…”