Blue laser

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Trails of a 20mW 405nm blacklight laser show clear fluorescense on some objects

A blue laser is a laser which emits light at a wavelength of between 360 and 480 nanometres.

Blue lasers are frequently semiconductor laser diode based on Gallium(III) nitride. These new devices have applications in many areas ranging from optoelectronic data storage at high density to medical applications.

History

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.

Thanks to prior development of many groups, including, most notably, professor Isamu Akasaki's group, Shuji Nakamura at Nichia Corporation and Sony Corporation in Anan (Tokushima-ken, Japan) made a series of inventions and developed commercially viable blue and violet semiconductor lasers. The active layer of the Nichia devices was formed from InGaN quantum wells or quantum dots spontaneously formed via self-assembly. 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.

Variants

Blue lasers usually operate at 405 nanometers but in general the operation of these devices was demonstrated between 360 and 480 nm. Currently there are also 473 nm (bright blue) laser pointers on the market but they are still very expensive.

The most popular 405 nm laser is not in fact blue, but appears to the eye as violet, a color for which a human eye has a very limited sensitivity. When pointed on many white objects the dot appears blue which is actually fluorescense, the same effect as a blacklight lamp. For display applications, where the "true blue" color is required, a wavelength of 450-460 nm is required. Such lasers are already on the market. The last big challenge is related to the construction of a "true green" InGaN laser (around 530 nm). Many companies demonstrated devices working at only slightly shorter wavelengths: 480-500 nm.^[1]

Applications

Areas of application of the blue laser include:

• Telecommunications
• Information technology
• Environmental monitoring
• Electronic equipment
• Medical diagnostics
• Micro projectors and displays

References

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