How CD Burners Work
If you’ve read How CDs Work from a previous issue, you already understand the basic idea of CD technology. CDs store music and other files in digital form. That means that the information on the disc is represented by a series of 1s and 0s. In standard CDs, these 1s and 0s are represented by millions of tiny bumps and flat areas on the disc’s shiny side.

The bumps and flats are arranged in a very long, continuous spiral path starting at the center of the disc. The CD player spins the disc while the laser pickup tracks the path of bumps and flats, converting them to a series of 1s and 0s. This digital information is converted to musical sounds by the machine’s electronics.

Writeable CD drives, or “burners,” also create patterns of 1s and 0s, but they do this without creating physical bumps and flats. The digital information is created through an ingenious process that uses a special dye. The disc is manufactured with a smooth reflective layer that rests on top of a layer of photosensitive dye. When the disc is blank, the dye is translucent, which means that light can pass through it. But when the dye layer is heated with a concentrated light of a particular frequency and intensity, it turns opaque. It darkens to the point that light can’t pass through.

By selectively darkening particular points along the CD track and leaving other areas of the dye translucent, you can create a digital pattern that a standard CD player can read. The light from the player’s laser beam will only bounce back to the sensor when the dye is left translucent (creating 1s), in the same way that it will only bounce back from the flat areas of a conventional CD. To “burn” a CD, the powerful “write laser” turns on and off in sync with the pattern of 1s and 0s from the source, such as an MP3 recording. CD-R (CD-Recordable) discs work in almost all CD players and CD-ROM drives and cost less than one dollar each.