Numerical modeling and uncertainty analysis of Light Emitting Diodes for Photometric Measurements Mohammed Z. U. Khan a , Mohammed Abbas a and Luai M. Al-Hadhrami a a Measurement Standards Laboratory, Center for Engineering Research, Research Institute, King Fahd University of Petroleum & Minerals, Dhahran, Saudi Arabia ABSTRACT With the rapid evolution of new, energy-efficient solid-state lighting (SSL) systems, a requirement has risen for new performance metrics and measurement methods to address their unique construction and operating conditions. In this paper, light propagation characteristics in light emitting diodes are analyzed for measurement uncertainty through numerical modeling and simulation. A general 2D EM simulator with PML boundary conditions is formulated to solve Maxwell’s equations using finite-difference time domain (FDTD) numerical method to describe the light propagation in LEDs. A practical GaN LED used in SSL systems is simulated for light propagation. The optical properties of dispersive materials are modeled using multi-pole Lorentz-Drude model. The input dipole source for the LED structure is modeled explicitly through a Gaussian pulse line source at a central wavelength of 460 nm corre- sponding to GaN emission. Finally, the expression for combined standard uncertainty in the light extraction efficiency due to uncertainties in inputs such as emission in the active layer and EM fields is developed using the GUM law of propagation of uncertainties. The uncertainty in GaN LED emission wavelength obtained from Full Width Half Maximum (FWHM) of the emission spectrum is computed to be 16.98 nm. Therefore, the uncer- tainty analysis model is then used to compute the corresponding uncertainties in the LED output measurements i.e. light extraction efficiency, LED output power and EM fields. Keywords: FDTD, LEDs, Optical Metrology, Photometric Measurements, Uncertainty Analysis, Maxwell’s Equations 1. INTRODUCTION Light Emitting Diodes (LEDs) are increasingly being introduced into the lighting market, and solid state lighting (SSL) is now becoming a reality. 1 But, this new technology still faces many challenges. Lighting consumes a huge amount of energy, currently 22% of all electricity consumed in the U.S. is for lighting purposes. White LED sources are expected to be twice, or more, energy-efficient than fluorescent lamps. 2 SSL is expected to have a big impact on a nations energy savings. Research on all photometric aspects of solid-state lighting sources is currently underway with emphasis on color quality and measurement methods for high-power light emitting diodes (LEDs) and other SSL products. New SSL calibration standards and measurement techniques are also being developed to improve the existing measurement methods. The development of new measurement methods has therefore become essential to commercialize solid-state lighting products. SSL measurement method development through experimental approaches may become expensive and time consuming. On the other hand, measurement method development through numerical modeling and simulation may prove to be comparatively efficient. Numerical models facilitate the rigorous study of the LED performance metrics before fabrication. They also help to develop the link between the material properties and the performance of the LED device. In this paper, the formulation of an efficient numerical simulation model for LED measurements is discussed and presented. The uncertainty analysis model is then developed using GUM law of propagation of uncertainty (ISO, 2009 a) for validation of the LED measurements. 3, 4 Further author information: (Send correspondence to M.Z.U.K.) M.Z.U.K.: E-mail: mdzia@kfupm.edu.sa, Telephone: +966 (13) 860 2868 M.A.: E-mail: abbas@kfupm.edu.sa, Telephone: +966 (13) 860 2468 Modeling Aspects in Optical Metrology V, edited by Bernd Bodermann, Karsten Frenner, Richard M. Silver, Proc. of SPIE Vol. 9526, 95260F · © 2015 SPIE · CCC code: 0277-786X/15/$18 · doi: 10.1117/12.2183599 Proc. of SPIE Vol. 9526 95260F-1 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 06/30/2015 Terms of Use: http://spiedl.org/terms