Blue laser

The term blue laser is frequently applied to semiconductor laser diode based on gallium nitride. These new devices have applications in many areas ranging from optoelectronic data storage at high-density to medical applications. Thanks to prior development of many, mostly Japanese, groups including most notably Prof Isamu Akasaki group, 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. The active layer of these devices was formed from InGaN quantum wells or quantum dots spontaneously formed via self-assembly. Until the mid 1990s, when blue semiconductor lasers were developed, 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. The new 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 lasers usually operate at 405 nanometers but in general the operation of these devices was demonstrated between 360 and 480 nm.

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Products

• BD (Blu-ray Disc)
• HD DVD
• Blue laser pointers.

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.

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)