Reflectance Matrix Approach to Absolute Photoluminescence Measurements with Integrating Spheres

Absolute measurements of photoluminescence are commonly performed using an integrating sphere setup, as this allows the collection of all emitted photons independent of the spatial characteristics of the emission. However, such measurements are plagued by multiple reflection effects occurring within the integrating sphere that make the sample illumination and sphere throughput sample dependent. To address this problem, we developed a matrix theory for integrating spheres with photoluminescent surfaces. In conjunction with a bispectral luminescence data set, this model allows for multiple reflection effects to be fully accounted for. The bispectral data is obtained by mounting both the sample and a non-luminescent reference on the sphere and permuting their positions in order to compare direct and diffuse sample illumination conditions. Experimental measurements of a photoluminescent standard confirm the validity of the method.