Information Storage and Retrieval for Probe Storage using Optical Diffraction Patterns

TL;DR

This paper introduces a fast optical diffraction-based method for storing and retrieving information in probe storage devices, utilizing diffraction patterns and low-complexity algorithms for efficient data recovery.

Contribution

It presents a novel optical diffraction technique for data retrieval in probe storage, including new modulation and detection schemes based on Fraunhofer diffraction theory.

Findings

Effective data retrieval using diffraction patterns for probe storage.

Low-complexity modulation and detection algorithms developed.

Performance remains robust for Fresnel number F<0.1.

Abstract

A novel method for fast information retrieval from a probe storage device is considered. It is shown that information can be stored and retrieved using the optical diffraction patterns obtained by the illumination of a large array of cantilevers by a monochromatic light source. In thermo-mechanical probe storage, the information is stored as a sequence of indentations on the polymer medium. To retrieve the information, the array of probes is actuated by applying a bending force to the cantilevers. Probes positioned over indentations experience deflection by the depth of the indentation, probes over the flat media remain un-deflected. Thus the array of actuated probes can be viewed as an irregular optical grating, which creates a data-dependent diffraction pattern when illuminated by laser light. We develop a low complexity modulation scheme, which allows the extraction of information stored in the pattern of indentations on the media from Fourier coefficients of the intensity of the diffraction pattern. We then derive a low-complexity maximum likelihood sequence detection algorithm for retrieving the user information from the Fourier coefficients. The derivation of both the modulation and the detection schemes is based on the Fraunhofer formula for data-dependent diffraction patterns. We show that for as long as the Fresnel number F<0.1, the optimal channel detector derived from Fraunhofer diffraction theory does not suffer any significant performance degradation.