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Intense and Efficient Yellow Light Source from Luminescent Concentrator

Reference number: 7228

Technology overview

Highly efficient, low-cost, solid-state sources of intense yellow light are still not available.

Whilst red and blue LEDs are industrystandard, the market still lacks efficient green and yellow LEDs and lasers. This deficit impedes a host of potential applications:

  • compact video projectors without hazardous mercury arc lamps;
  • vascular laser surgery and beauty therapies;
  • photochemical reactors for drug manufacture;
  • optically-pumped MASERs; etc.

Luminescent concentrators (LCs) can function as light sources. A further improved such light source has been developed by researchers at Imperial College London. This LC-based light source is capable of continuously outputting ~50 W of yellow light through a 1.6-by-1.6 mm square aperture. It is based on an air-cooled strip of Cerium(Ce3+)-doped Yttrium Aluminium Garnet (YAG) sandwiched between commercially-available arrays of royal blue (460 nm) Indium Gallium Nitride (InGaN) pump diodes.

Attached to one end of the strip is a "fish-tail” that converts light flowing across the strip’s high-aspect-ratio rectangular exit aperture into light that exits through a more convenient square or circular aperture of the same crosssectional area. Spectrally, the outputted light is centred around 575 nm with a full-width-half-maximum spread of ~76 nm.

The Ce:YAG strip's high cross-sectional aspect ratio enables waste heat to be effectively removed via (a) solid thermal conduction along the strip’s “thin” direction, combined with (b) forced-air or water cooling over the strip’s two large optical input (pump) surfaces spanning its width and length. With a wider (and longer) fishtail, the concentrator’s output power can be upscaled simply by increasing the strip’s lateral width.

Neither its length nor its thickness, nor even the dopant concentration of the luminophore within it, need be changed. Such upscaling does not alter –and thus cannot compromise– the cooling path. The area available for cooling grows proportionally with the output power required.


Benefits over existing designs of luminescent concentrator:

  • Greater optical output power for a given device length
  • Enhanced colour stability (reduced wavelength shifts from heating effects)

Intellectual Property Information

European Patent Number (Patent Granted. Validated in United Kingdom, France, Germany, Netherlands and Belgium): EP15794621.1
United States Patent Number: US15520287

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Valeska Gonzalez

Industry Partnerships and Commercialisation Executive, Engineering


+44 (0)20 7594 6893

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