CD and DVD Duplication - Lasers

Laser technology is a vital component of CD Duplication, in fact it is the foundation upon which the technology of CDs developed and therefore integral to the processes involved. As CD technology has developed over the past 40 years, so too have the lasers used developed and advanced to produce new capabilities and uses of CDs.

With lasers being a vital part of the Duplication process, not just in reading CDs, the development in laser technology has therefore had important implications for CD Duplication, while the laser process used during duplication will impact the lasers used at the CD reading stage.

Originally, CAT lasers were used to read CDs, with an infrared wavelength of 780 nm. Subsequently the wavelength has been reduced to produce DVDs, using a reading wavelength of 650 nm, while Blu-Ray discs use a lower wavelength still of a violet wavelength of 405 nm. This development of using smaller wavelength lasers has been to increase the amount of data that can be stored onto a disc. Particularly with the development of using discs to store imagery and video, rather than just audio and ROM data, much more data has been needed to be stored on a single disk. With the physical size of discs remaining the same, this data has had to be packed much closer together in order to fit it all on. As a result, lasers with shorter wavelengths have had to be developed in order to read this now more compact data storage.

Inevitably, as well as requiring a shorter laser wavelength to read a disc, so shorter laser wavelengths have been required in order to 'write' the data onto the disc during the CD and DVD Duplication process. During Duplication, a laser is used to change the reflectivity of the disc surface, with these variations in reflections detected by the laser in the disc reading device. It therefore follows that the changes in reflection of this disc must be shorter, and therefore the laser that creates them must also be so.

Lasers used during Duplication are called Laser Beam Recorders (LBR). These laser machines can vary the wavelength of the laser, depending on what is needed and what the disc is to be used for, to create CDs, DVDS, Blu-ray and other disc types. LBRs use either Photoresist Mastering or Non-Photoresist Mastering (also known as Dye-Polymer mastering) to write to the discs. Photoresist mastering uses discs with light-sensitive surface materials that change reflection when exposed to the laser, while Dye-Polymer mastering use discs with a Dye-Polymer surface material which evaporates when exposed to concentrated energy produced by the laser at the required points on the disc. Each of these techniques has different benefits, and also requires a different laser setup to write to the different disc types.

Lasers used to Duplicate a disc are much more powerful than those used to read the disc. This makes sense, as a reading device does not want to alter the disc surface and affect the data stored on it, whereas this is the exact purpose of a LBR. An LBR needs to operate at a power setting that produces enough energy to alter the surface of the disc, which is currently around 200mW, while disc readers run at around 5mW. This allows readers to run at a lower power, saving energy, and also allows a significant differentiation between the two power settings to avoid readers inadvertently causing damage. In order to allow this, disc surface materials that can be moulded at the higher power setting while remain unaffected at the lower setting of the reading lasers have to be selected.

Lucy Lewis is new at writing articles, with her charming and inquisitive mind she wants to explore the literacy world in a whole different light. So watch out for further articles.