Limitations to emission spot size in laser lighting

Laser lighting is an emerging technology to generate high luminance lighting. To achieve high luminance or high luminous exitance, the light emitter must have high flux and small size simultaneously. When laser light is focused to a small spot size on the phosphor material, the two main limitations are saturation of the phosphor material and the spot size of the generated light. Here, we investigate experimentally and numerically the spot size of laser lighting dependent on the spot size of the incident laser light and the material properties of the wavelength converting phosphor material. We find numerically that the spot size of the generated white light is significantly influenced by the phosphor properties. The spot size of the white light determines the étendue and thereby the possibility to collect and shape the light. This has important implications in applications of laser lighting.