The remote phosphor method has provided significant improvement in overall LED lighting system efficiency by reducing the number of photons absorbed at the LED chip. However, increased demand for higher light output from smaller light engines has resulted in high radiant energy and heat densities on the phosphor layer. The problem is exacerbated by the phosphor conversion efficiency decreasing with increased operating temperature in the remote phosphor layer. A higher operating temperature can negatively affect performance in terms of luminous efficacy, color shift, and life. In cases such as this, the system's performance can be improved through suitable thermal management that reduces the phosphor layer temperature. In this study, we present the first investigation to experimentally quantify the operating temperature and optical performance effects of using a dedicated phosphor layer heat sink solution as a thermal management strategy to reduce phosphor layer operating temperature. The effects of heat sink geometry and material parameters on phosphor layer operating temperature and optical performance were investigated. The experimental results showed a decrease in phosphor layer operating temperature with an increase in phosphor layer heat sink interface area, while the total radiant power decreased. Ray-tracing simulations identified the low surface reflectance of the heat sink interface area as the cause of this decrease in radiant power. A finite element model was developed from the experimental results to understand the decrease in phosphor layer operating temperature with increased heat sink interface area. This simulation work was used in identifying the causes affecting observed optical and thermal performance in the short-term experiments. The study also investigated the long-term performance of phosphor layer heat sinks and the findings are reported. (C) 2017 Elsevier Ltd. All rights reserved.