Method and apparatus for optical data storage and/or retrieval by selective alteration of a holographic storage medium

A method for optical data retrieval from an optical storage device, said optical storage device comprising an optical data storage medium having a periodic, spatially-modulated refractive index, said periodic, spatially-modulated refractive index defining a first Bragg-reflection condition, and data stored thereon as localized alterations of said optical data storage medium, said localized alterations defining a second Bragg-reflection condition, said method comprising the steps of:

• choosing a frequency of a retrieval beam of electromagnetic radiation that is Bragg-matched to said first Bragg reflection condition;
• focusing a retrieval beam at a plurality of localized storage points within said optical data storage medium to form an output beam;
• and
• detecting said output beam to retrieve said stored data.

A method for optical data retrieval from an optical storage device, said optical storage device comprising an optical data storage medium having a periodic, spatally-modulated refractive index, said periodic, spatially-modulated refractive index defining a first Bragg-reflection condition, and data stored thereon as localized alterations of said optical data storage medium said alterations defining a second Bragg-reflection condition, said method comprising the steps of:

• choosing a frequency of a retrieval beam of electromagnetic radiation that is Bragg-matched to said second Bragg reflection condition;
• focusing a retrieval beam at a plurality of localized storage points within said optical data storage medium to form an output beam;
• and
• detecting said output beam to retrieve said stored data.

An optical data storage system comprising:

• an optical data storage medium, said medium having a periodic, spatially-modulated refractive index, said periodic, spatially-modulated refractive index defining a first Bragg-reflection condition;
• a storage beam of electromagnetic radiation which causes a local alteration of said optical data storage medium when focused onto a localized region within said optical data storage medium, said local alteration defining a second Bragg-reflection condition;
• and
• optics means for focusing said storage beam at a plurality of localized storage points within said holographic storage medium.

An optical data retrieval system, said system comprising:

• an optical data storage device comprising:
• an optical data medium having a periodic, spatially-modulated refractive index, said periodic, spatially-modulated refractive index defining a first Bragg reflection condition;
• and
• data stored thereon as localized alterations of said optical data medium, said localized alterations defining a second Bragg reflection condition;
• a retrieval beam of electromagnetic radiation, having a frequency matched to said first Bragg reflection condition;
• optics for focusing said retrieval beam onto a plurality of localized storage points within said optical data storage device and forming an output beam;
• and
• an optical detector for detecting said output beam to retrieve said stored data.

An optical data retrieval system, said system comprising:

• an optical data storage device comprising:
• an optical data storage medium having a periodic, spatially-modulated refractive index, said periodic, spatially-modulated refractive index defining a first Bragg reflection condition;
• and
• data stored thereon as localized alterations of said optical data storage medium, said localized alterations defining a second Bragg reflection condition;
• a retrieval beam of electromagnetic radiation, having a frequency matched to said second Bragg reflection condition;
• optics means for focusing said retrieval beam onto a plurality of localized storage points within said optical data storage device and forming an output beam;
• and
• an optical detector for detecting said output beam to retrieve said stored data.