Brewster-coupling-based thin film filter design for wide-angle high-efficiency phosphor emission

In this paper, we propose a bandpass filter design method for laser activated remote phosphor (LARP) usage. This design uses the Brewster angle as the passband instead of a wavelength passband. Two advantages are found with this design. First, the transmittance at the Brewster angle is naturally 100%, which is optimal. Second, the stop band reflectance with a wide angular range is better compared to the dichroic filter in a LED-phosphor model. We design two optical thin film filter samples to enhance the extraction efficiency of YAG:Ce phosphor with the same design criteria, objective function, and optimization algorithm. With 50-layer designing, the optical losses for LARP are 23.7% and for LED-phosphor are 26.0%.