Abstract
A luminescent concentrator functioning as a bright source of yellow light is reported. It comprises a waveguide made of cerium-doped YAG crystal, in the form of a long-thin rectangular strip, surrounded by flowing air and optically pumped from both sides with blue light from arrays of high-efficiency InGaN LEDs. Phosphor-converted yellow light, generated within the strip, is guided to a glass taper that is butt-coupled to one of the strip's end faces. Up to 20 W of optical power, centered on 575 nm with a linewidth of 76 nm, can be continuously radiated into air from the taper's 1.67 mm × 1.67 mm square output aperture. The intensity of the outputted light is significantly greater than what any yellow (AlGaInP) LED can directly produce (either singly or arrayed), with only a modest increase in linewidth. Furthermore, the wall-plug efficiency of the source exceeds that of any yellow laser. The concept allows for further substantial increases in intensity, total output power and wall-plug efficiency through scaling-up and engineering refinements.
Highlights
The spectral sensitivity of the cone opsins in a human retina and the spectral absorptance of hemoglobin in human blood mean that significant consumer applications, such as full-color video projection and vascular skin surgery, require intense sources of yellow light
On the scales set by current laser technology, this quasi-continuous light need only be of modest instantaneous power, intensity, and monochromaticity
For reasons of practicality and economy, it should be generated at high wall-plug efficiency (WPE)
Summary
The spectral sensitivity of the cone opsins in a human retina and the spectral absorptance of hemoglobin in human blood mean that significant consumer applications, such as full-color video projection and vascular skin surgery, require intense sources of yellow light. In these applications, the light needs to be supplied either continuously, i.e., CW, or in pulses hundreds of microseconds in duration. The high operating temperatures and long warm-up times of copper-vapour lasers and the explosion hazard and limited lifetime of high-pressure xenon arc lamps make neither consumer-friendly technologies.
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