Holographic Data Storage System (HDSS) program was a

US Federal government The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a feder ...

-funded consortium on

holographic data storage Holographic data storage is a potential technology in the area of high-capacity data storage. While magnetic and optical data storage devices rely on individual bits being stored as distinct magnetic or optical changes on the surface of the recor ...

Teledyne Technologies Teledyne Technologies Incorporated is an American industrial conglomerate. It was founded in 1960, as Teledyne, Inc., by Henry Singleton and George Kozmetsky. From August 1996 to November 1999, Teledyne existed as part of the conglomerate Al ...

, IBM and Stanford University, created in 1995. Work on the program began in 1994 and was funded by

DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Ad ...

History

The holographic data storage system was created with the initial goals of developing several key components for the system, including a high-capacity, high-bandwidth

spatial light modulator A spatial light modulator (SLM) is an object that imposes some form of spatially varying modulation on a beam of light. A simple example is an overhead projector transparency. Usually when the term SLM is used, it means that the transparency can ...

used for data input; optimized

sensor array A sensor array is a group of sensors, usually deployed in a certain geometry pattern, used for collecting and processing electromagnetic or acoustic signals. The advantage of using a sensor array over using a single sensor lies in the fact that an ...

s for data output; and a high-power red

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

Laser A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The firs ...

. At the same time, the HDSS researchers were to explore issues relating to the optical systems architecture (such as

multiplexing In telecommunications and computer networking, multiplexing (sometimes contracted to muxing) is a method by which multiple analog or digital signals are combined into one signal over a shared medium. The aim is to share a scarce resource - a ...

schemes and access modes), data encoding and decoding methods,

signal processing Signal processing is an electrical engineering subfield that focuses on analyzing, modifying and synthesizing '' signals'', such as sound, images, and scientific measurements. Signal processing techniques are used to optimize transmissions, ...

techniques, and the requirements of target applications. Into the program's final year, progress has been such that consortium member, IBM Research Division, believed that

hologram Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other Holography#Applications, applic ...

s could hold the key to high-capacity data storage in the next millennium.

Mechanism

Large amounts of data can be stored holographically because lasers are able to store pages of electronic patterns holographic storage – sometimes referred to as 3D storage within special optical materials as opposed to just on the surface. In traditional

holography Holography is a technique that enables a wavefront to be recorded and later re-constructed. Holography is best known as a method of generating real three-dimensional images, but it also has a wide range of other applications. In principle, i ...

, each viewing angle gives a different aspect of the same object. With holographic storage, however, a different 'page' of information is accessed. Holographic storage uses two laser beams, a reference and a data beam to create an

interference Interference is the act of interfering, invading, or poaching. Interference may also refer to: Communications * Interference (communication), anything which alters, modifies, or disrupts a message * Adjacent-channel interference, caused by extra ...

pattern at a medium where the two beams intersect. This intersection causes a stable physical or chemical change which is stored in the medium. This is the write sequence. During the reading sequence, the action of the reference beam and the stored

interference pattern In physics, interference is a phenomenon in which two waves combine by adding their displacement together at every single point in space and time, to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive ...

in the medium recreates this data beam which may be sensed by a detector array. The medium may be a rotating disk containing a

polymer A polymer (; Greek ''poly-'', "many" + '' -mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic and ...

ic material, or an optically sensitive single

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macr ...

. The key to making the holographic data storage system work is the second laser beam which is fired at the crystal to retrieve a page of data. It must match the original reference beam angle exactly. A difference of a thousandth of a

millimeter file:EM Spectrum Properties edit.svg, 330px, Different lengths as in respect to the electromagnetic spectrum, measured by the metre and its derived scales. The microwave is between 1 meter to 1 millimeter. The millimetre (American and British Eng ...

will result in failure to retrieve the data. Holography is expected to be of value in

archival An archive is an accumulation of historical records or materials – in any medium – or the physical facility in which they are located. Archives contain primary source documents that have accumulated over the course of an individual ...

or library storage applications where large quantities of data are required to be retained at the lowest costs possible.

Apparent benefits

Since it involves no moving parts, holographic data storage will be more reliable than existing

hard disk A hard disk drive (HDD), hard disk, hard drive, or fixed disk is an electro-mechanical data storage device that stores and retrieves digital data using magnetic storage with one or more rigid rapidly rotating platters coated with mag ...

technologies. IBM has already demonstrated the possibility of holding 1 TB of data in a crystal the size of a sugar cube and of data access rates of one trillion bits per second. The major challenge ahead is expected to be the development of a rewritable form of holographic storage. During CES 2006, a workable holographic drive was tested and stored 300 GB of memory compared to

Blu-ray The Blu-ray Disc (BD), often known simply as Blu-ray, is a digital optical disc data storage format. It was invented and developed in 2005 and released on June 20, 2006 worldwide. It is designed to supersede the DVD format, and capable of s ...

's 100 GB. It has been announced that hologram disks will be a post-Blu-ray storage device.

References

{{Reflist Holographic data storage Computer storage devices