Browse Prior Art Database

Multi-Layer Optical Memory Device

IP.com Disclosure Number: IPCOM000035997D
Original Publication Date: 1989-Aug-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 2 page(s) / 63K

Publishing Venue

IBM

Related People

Kano, SS: AUTHOR [+2]

Abstract

This article describes a new concept of a 3D optical memory which uses a thin film multi-layer structure, which enables realizing N times higher volume density for a write-once disk system (N being the number of layers).

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Multi-Layer Optical Memory Device

This article describes a new concept of a 3D optical memory which uses a thin film multi-layer structure, which enables realizing N times higher volume density for a write-once disk system (N being the number of layers).

The 3D disk consists of N memory layers (1 micron each, sandwiched by buffer layers of 10 microns). A bit is written by a two-photon process in one memory layer because the fundamental frequency interacts with the material only at the focal point to change its molecular structure (two-photon bleaching). This bit is read by THG (third harmonics) of laser radiation. The signal comes only from the desirable memory layer. With a high peak power laser, the read and write process will be completed within the order of 20 ns.

(Image Omitted)

The 3D disk structure is shown in Fig. 1. The typical thickness of each layer is given in Fig. 2. A memory layer is made of the material with high chi-3 such as PDHS (Poly-(di-n-hexyle)-silane), and the thickness is 1 micron. A buffer layer of 10-micron thickness has much smaller chi-3 than that of the memory layer.

The NLO (Nonlinear Optical) process ensures that the data are written/read only in/out of the memory layer where the light beam is focused. The thickness of the layer is designed to have the optimum signal intensity as well as to be free from spurious NLO effects such as self-focusing. Buffer layers are required to separate out adjacent memory layers from the focussed one...