Monitoring the health of laser-driven phosphor-converted white light source using spectral interference technique

Abstract

Abstract We report an innovative method for early monitoring of the Opto-thermal health of laser-driven phosphor-converted white light source using low coherence spectral interference technique. A phosphor layer was irradiated using a high-power laser source in reflection mode and the broadband light generated from the phosphor layer was made incident onto a common path interferometer. The interferometer was made of two optically flat glass plates stacked together with minimum optical path difference between the two reflecting components (≤ 1µm). The constructive and destructive interference peaks were recorded in the spectrum. A significant change in Stokes shift was observed from spectral interference peak shifts in a short interval of time and this helped in analyzing the phosphor Opto-thermal behaviour from thermal initialization to the material saturation. The minimization of the observed changes in the Stokes shift can be helpful in the material development process for thermally stable illumination.