Brewster angle excitation dichroic for transmissive laser activated remote phosphor applications

Many solid-state lighting (SSL) applications require high luminance and high luminous flux. Applications include projection, automotive lighting, stage lighting, medical, and other areas. Typical systems use light-emitting diodes to excite phosphors through a dichroic coating which passes excitation light but reflects emission light. However, these coatings are imperfect and a significant fraction of emission light is lost through the coating. Particularly at the Brewster angle, the coating is always transmissive and gives photon loss no matter how well the rest of the coating is optimized. In addition, light-emitting diodes do not have the luminance necessary for very bright applications. By coupling in p-polarized pump laser light at the Brewster angle, it’s window liability is converted into an asset.
 

Advantages:

-Significantly more efficient with simpler coating design.
-The design constraints of the dichroic coating can now be substantially relaxed, and the coating can be more easily designed to be omni-reflective over all wavelengths (with a single passband at the Brewster angle).
- Substantial quantitative improvements in the efficiency of photon emission per input photon.

 

Binghamton University RB587

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