Intense, highly-efficient solid-state yellow light source based on rare-earth-doped luminescent concentrator

Highly efficient, low-cost, solid-state sources of intense yellow light are still not available. This deficit impedes a host of potential applications: compact video projectors without hazardous mercury arc lamps, vascular laser surgery and beauty therapies (e.g. wrinkle removal), photo-chemical reactors for drug manufacture, optically-pumped organic MASERs etc. Though developed as flat-panel light collectors for solar cells, luminescent concentrators (LCs) can compete successfully against lasers as light sources in applications requiring high optical power yet only modest light intensity (luminance). LCs offer higher wall-plug efficiencies, greater mechanical ruggedness and lower fabrication costs. In comparison: both conventional flash-lamp-pumped pulsed (Rhodamine 6G) liquid dye lasers, and CW (diode-pumped) solid-state lasers (such as Toptica’s SodiumStar) offer wall-plug efficiencies of around 2%; both require precise optical alignment; neither can be regarded as low-cost. Rare-earth-doped materials show promise as LCs due to their large Stokes shifts, reduced reabsorption losses, and capability to operate at high dissipated power densities. We report here, the realization of an LC-based light source, capable of continuously outputting ~ 50 W of yellow light through a 1.6-by-1.6 mm square aperture, with substantially higher wall-plug efficiency than any laser. It is based on an air-cooled strip of Cerium (Ce3+) - doped Yttrium Aluminum Garnet (YAG) sandwiched between commercially-available arrays of royal blue (460 nm) Indium Gallium Nitride (InGaN) pump diodes. The outputted light is centered around 575 nm with a full-width-half-maximum (FWHM) ~ 76 nm. Our prototype device works well and we believe that it has significant potential in the applications named above.