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Panasonic UV lasers and phosphors energise white lights

The company's newly developed technology will enable wider variation in design and a higher brightness and smaller form factor in data projectors and vehicle headlights
Panasonic Corporation has developed a semiconductor white light source capable of outputting luminous flux in the 10,000-lumen class.

An increased light output was achieved due to the high-efficiency, low-loss design and modularisation of the near-ultraviolet semiconductor laser used in the light source.

A high luminous flux of white light was realised through the development of a phosphor material that is not subject to luminance saturation even when irradiated with high-intensity laser light.

Luminance saturation is when the optical power may decline as the intensity of incident radiation increases.

The use of a laser with a smaller light-emitting area and superior light emission directionality to LEDs has made a compact optical configuration that boasts higher brightness and a smaller form factor possible. Panasonic says this technology opens the way to the greater use of semiconductor light sources in the projection and lighting market.

The new technology has the following features:

- By increasing the output of the near-ultraviolet laser in the light source to ten times that of a conventional Panasonic laser, the industry's highest light output of 60 watts (W) has been achieved. This is based on a survey by Panasonic on near-ultraviolet laser up to May 24th, 2013. The miniaturised laser module, a component where two or more semiconductor lasers are mounted functioning as a light source, can be incorporated into a wider range of equipment.

- The use of a newly developed phosphor material has increased blue light emissions by 40 percent when irradiated with 60W near-ultraviolet semiconductor laser light. This contributes to the realisation of a 10,000-lumen class high-luminous flux white light source through the red, green and blue phosphors.

- The generation of red, green and blue lights from only one type of laser light using a rotating phosphor wheel simplifies the optical system and ensures that the laser is projected directly onto the screen. The phosphor wheel is a component where light is shined onto the surface of a disc, onto which phosphor has been applied, which is then rotated by a motor on the central shaft, continuously creating phosphor light.

This development is based on the following new technologies:

- High-output, low-loss laser design technique with wider near-ultraviolet laser optical waveguide and optimised light loss control.

- Phosphor material technology that utilises the high-density crystalline structure of SMS (Sr3MgSi2O8) phosphor to control the density of the luminescent centre and thus prevent luminous saturation.

- Wavelength conversion technology that uses a rotating phosphor wheel that absorbs near-ultraviolet laser light and converts it to red, green and blue luminescent light.

Conventional laser white light sources require multiple visible light semiconductor lasers that emit blue and other colours, which creates a trade off between small form factor and high brightness. Some laser wavelengths are even projected directly, without passing through the phosphor material.

Conventional phosphors are not suitable for use as high-intensity light sources, as they are subject to significant luminance saturation when laser light is focused on them.

Panasonic holds 39 patents in Japan and 22 overseas patents, including pending applications, for this development.

This newly developed technology received the Distinguished Paper Award from the Society for Information Display (SID), an international conference for displays and related products held last week.

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