Blue laser
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Blue lasers have applications in many areas ranging from opto-electronic data storage at high-density to medical applications. Until the mid 1990s, blue lasers were large and expensive gas laser instruments which relied on population inversion in rare gas mixtures and needed high currents and strong cooling. In the mid 1990s Shuji Nakamura at Nichia Chemical Industries in Anan (Tokushima-ken, Japan), made a series of inventions and developed commercially viable blue and violet semiconductor lasers based on gallium nitride compound sectors by using quantum wells or quantum dots spontaneously formed via self-assembly. This invention enabled the development of small, convenient and low priced blue, violet and ultraviolet UV lasers which had not been available before and opened the way for applications such as high-density HD DVD data storage and Blu-ray discs. The shorter wavelength allows it to read discs containing much more information.
Blue laser light usually has a relatively low input-to-power efficiency. Blue lasers usually operate at around 472 nanometers.
The use of indium gallium nitride as a semiconductor material suitable for formation of quantum heterostructures has been proposed. Recently, CdS/ZnS quantum dots have been used as the gain material in spherical Whispering Gallery Mode lasers; see Applied Physics Letters, 2005, 86:073102.
Shuji Nakamura built his blue laser prototype from the gallium nitride crystal developed by Unipress, the Warsaw Center for High Pressure Research, part of the Polish Academy of Sciences.
- Further information: Polish blue laser
Blue lasers are also used in blue laser pointers.
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[edit] Products
[edit] DPSS lasers
A blue DPSS laser is an alternative to a blue semiconductor laser. They most often lase at 473 nm, which is produced by frequency doubling of 946 nm laser radiation from a diode-pumped Nd:YAG or Nd:YVO4 crystal. For high output power BBO crystals are used as frequency doublers. For lower optical powers, KTP or periodically poled KTP (PPKTP) crystals are used.
[edit] Further reading
- Shuji Nakamura, Gerhard Fasol, Stephen J. Pearton, The Blue Laser Diode : The Complete Story, Springer; 2nd edition, October 2, 2000, (ISBN 3-540-66505-6)
