What Type of Storage Devices Use Laser Technology?

The computer you are sitting at reading this article probably contains a laser. If you went out to watch a movie last night, you probably watched it on a machine using a laser. The laser has become the storage media device of choice since Sony and Phillips first developed it in 1985. This article will discuss the basics of how lasers are used to store and retrieve information, their advantages and disadvantages, the most common types of lasers, and their future outlook.

How a Laser Stores Information

The computer stores information in a format which is generally referred to as "binary." Binary is defined as "characterized by or composed of two different parts or components" (American Heritage Dictionary, Second College Edition, Houghton Mifflin Co, Boston). The typical light switch on the wall is an example of a binary device. It's either on, or it's off. Typically, this is annotated as a series of 1's and 0's.
Essentially, what a laser does is shine onto the device as directed by the storage device and a sensor determines whether the light from the laser is reflected back on a particular location on the device, or scattered and not returned. It just does this very quickly on a rapidly rotating surface. This is why when you turn a CD from side to side, the light reflection changes as you vary how you are holding it. Originally, laser storage devices were able to read the data only, much in the way you read a book.
This changed in 1997 with the introduction of the read/write-able compact disc. The CD-RW's laser is more powerful and able to alter the face of the CD in a process referred to, colloquially, as burning.

The Advantages

Using lasers for storage has a number of advantages over the older method of storing large amounts of information for computers. Prior to laser storage, the only method for storing information semi-permanently for a computer was to do so magnetically. It used magnetic polarity, which is positive or negative, to store the data. In fact, the modern hard drive still works in this manner. The reason why this has fallen out of favor for external data is simply that the floppy diskette -- as it was called -- was simply too subject to outside interference. Many is the college student who, after having spent all night on that big report and saving it to a floppy for later, made the critical mistake of using a refrigerator magnet to put it on the door so it wouldn't be forgotten in the morning, only to discover to their horror that the magnet had destroyed the report. Also, comparatively, floppy diskettes held very little information; 1.44 MB as compared to the 50 GB of the modern Blu-ray player. Put simply, the major advantage of laser storage is that it holds more information and is less subject to breakage and environmental damage.

The Disadvantages

The reason why laser-based media is not used for all computer information storage is that read/write-able discs tend to wear out very quickly with multiple uses since the laser is literally thinning the disc with each rewrite. Magnetic storage systems, in contrast, can be written over and over again without wearing out because the polarity is simply being rearranged, not physically destroyed.
The only other minor disadvantage comes from the fact that chips and cracks in the surface of the disc can obscure the data below, causing false reflections and corrupting the data. While they are not as vulnerable to an ill-placed magnet, throwing them loosely in a purse, for example, with keys and such is a great way to render the discs useless.

The Major Storage Media Types

There are roughly five types of storage media. While they all look about the same, they work slightly differently.
CD and CD-ROM: While they're not exactly the same, they are close enough to be considered together. These are mass produced in a factory. CDs or compact discs were created to carry music. They were later converted over to be used for the storage of computer programs. Their most distinctive feature is that they can not be altered without destroying the compact disc
DVDs: The digital video disc or digital versatile disc is much like the CD-ROM above, however it has a much more compact storage methodology, allowing it to store movies, and is the most common media for storing video games today. Again, it can't be changed without destroying the DVD.
CD-R and DVD-R: The major difference between a standard compact disc or digital video disc is that the media, or the silvery disc, can be written to once. Once written to, it can't be changed without mangling or destroying the disc.
CD-RW and DVD-RW: Most modern computers come with a drive capable of using these discs, and they have largely replaced the 3.5-inch floppy disk drive. "RW" simply means read/write. The chief advantage of this format is that it can be written to and read. In general, it is also the slowest of the formats.
Blu-ray Discs: These are the latest of version of the digital video disc. They are able to hold tremendous amounts of data and are able to recover that information fairly quickly, as much as 50 GB. Currently, Blu-ray discs are mostly used for the next generation of movie formats, but it will likely not be long before Blu-ray migrates to the computer and quite possibly takes the place of the older DVD-RWs entirely since it's backwards compatible with the older DVDs and CDs.
Despite the different names, most of these items work under the same basic method as previously discussed.

The Future

Pioneer is currently developing a Blu-ray disc that layers the information on the disc -- basically a three-dimensional storage system -- where the optical system reads not only whether or not the item reflects, but on which layer it reflects. The current version can store about 500 GB, or as much space as many modern hard drives. This system could be referred to as holographic, which is sometimes used to create three-dimensional pictures in glass and similar substances through the use of lasers. Several companies are looking at this application for storing information on DVDs.