Blu-ray Disc (BD) is the name of a next-generation optical disc format jointly developed by the Blu-ray Disc Association (BDA), a group of the world's leading consumer electronics, personal computer and media manufacturers (including Imation, LG, Verbatim, Philips, Samsung, Sony and TDK). The format was developed to enable recording, rewriting and playback of high-definition video (HD), as well as storing large amounts of data. The format offers more than five times the storage capacity of traditional DVDs and can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. Blu-ray products can easily be made backwards compatible with CDs and DVDs through the use of a BD/DVD/CD compatible optical pickup unit. The benefit of using a blue-violet laser (405nm) is that it has a shorter wavelength than a red laser (650nm), which makes it possible to focus the laser spot with even greater precision. This allows data to be packed more tightly and stored in less space, so it's possible to fit more data on the disc even though it's the same size as a CD/DVD. This together with the change of numerical aperture to 0.85 is what enables Blu-ray Discs to hold 25GB/50GB. Although the Blu-ray specification has been finalized, engineers continue working to advance the technology. Quad-layer (100 GB) discs have been demonstrated. And TDK announced in August that they have created a working experimental Blu-ray Disc capable of holding 200 GB of data on a single side, using six 33 GB data layers. Such discs would almost certainly not work on some of today's Blu-ray players, as these devices are only designed and tested on discs that meet the current specification. Of course, six-layer discs or other advanced techniques may be included in a later generation of the Blu-ray spec, when they can be reliably mass-produced.