Static ceramic converters for laser pumped phosphor light sources with white light emission

Laser pumped phosphor light sources are already widely used in light engines for digital projection. This etendue-limited application benefits from the high luminance that is achieved by irradiating yellow or green ceramic phosphors with blue laser light. These laser pumped phosphor light sources serve the green and red color channels of the projectors. Other etendue-limited applications such as fiber or microscope illumination require high luminance white light instead of light of a single color. Properly designed ceramic phosphors fulfill this task by direct mixing of the yellow luminescent emission with the diffusely reflected laser light on the spot. We present a range of ceramic converters with a variety of emission characteristics such as correlated color temperature or centroid wavelength, and characterize them with respect to application-related key parameters. In particular, we investigate the impact of irradiance, laser spot size, and device cooling. Generalization of the measurement data with support of numerical modeling results in a basic framework for system design that supports the selection of the best-suited converter material for a given application.