Paula Acuña
Katholieke Universiteit Leuven
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Publication
Featured researches published by Paula Acuña.
Optics Express | 2014
Paula Acuña; Sven Leyre; Jan Audenaert; Youri Meuret; Geert Deconinck; Peter Hanselaer
Light-emitting diodes (LEDs) are becoming increasingly important for general lighting applications. The remote phosphor technology, with the phosphor located at a distance from the LEDs, offers an increased extraction efficiency for phosphor converted LEDs compared to intimate phosphor LEDs where the phosphor is placed directly on the die. Additionally, the former offers new design possibilities that are not possible with the latter. In order to further improve the system efficiency of remote phosphor LEDs, realistic simulation models are required to optimize the actual performance. In this work, a complete characterization of a remote phosphor converter (RPC) consisting of a polycarbonate diffuser plate with a phosphor coating on one side via the bi-directional scattering distribution function (BSDF) is performed. Additionally, the bi-spectral BSDF which embraces the wavelength conversion resulting from the interaction of blue light with the RPC is determined. An iterative model to predict the remote phosphor module power and photon budget, including the recuperation of backward scattered light by a mixing chamber, is introduced. The input parameters for the model are the bi-spectral BSDF data for the RPC, the emission of the blue LEDs and the mixing chamber efficiency of the LED module. A good agreement between experimental and simulated results was found, demonstrating the potential of this model to analyze the system efficiency with errors smaller than 4%.
IEEE Photonics Journal | 2015
Paula Acuña; Sven Leyre; Jan Audenaert; Youri Meuret; Geert Deconinck; Peter Hanselaer
Remote phosphor light-emitting diode (LED) modules could offer advantages over intimate white phosphor converted LEDs in terms of phosphor operation temperature, light extraction efficiency, and angular color uniformity. Existing commercial devices show a large variety with respect to the dimensions of the mixing cavity, which raises a question about the optimization of the topology. A simplified simulation model applying a two-wavelength approach and considering the remote phosphor as one virtual surface to which three bidirectional scattering distribution functions are attributed (respectively, describing the blue-blue, blue-yellow, and yellow-yellow interactions) is developed and validated. This model has been used to analyze the impact of the cylindrical mixing cavity parameters such as the absolute reflectance, the diffuse-to-specular reflectance ratio, and the height of the mixing cavity, as well as the pitch and angular full-width at half-maximum of the LEDs on the extraction efficiency, the yellow-to-blue ratio, and the irradiance uniformity. It can be concluded that in order to increase the efficacy substantially, the recuperation of the backward emission of the converted light can only be increased by avoiding further interaction with the phosphor plate. To this extent, topologies other than cylindrical mixing cavities must be considered.
Optics Express | 2014
Sven Leyre; Jana Ryckaert; Paula Acuña; Jan Audenaert; Youri Meuret; Guy Durinck; Johan Hofkens; Geert Deconinck; Peter Hanselaer
To perform adequate simulations of luminescent cascade systems, a hybrid method combining a commercial ray tracer and a programming tool is presented. True Monte Carlo algorithms for luminescent materials, treating each ray individually, are adapted to allow wavelength conversion of ray sets. Two solutions for the wavelength conversion of ray sets are discussed: a random approach, where absorption events are randomly selected to create emission events, and a combined approach, where information from multiple absorption events is combined to create emission events. Both methods are applied to simulate the performance of a virtual remote phosphor light-emitting diode module. When using the combined approach, the required computation time to achieve sufficient accuracy is a factor 2 lower, compared to the time required when applying the random approach.
Proceedings of SPIE | 2014
Sven Leyre; Jana Ryckaert; Paula Acuña; Jan Audenaert; Youri Meuret; Johan Hofkens; Guy Durinck; Geert Deconinck; Peter Hanselaer
Monte Carlo ray tracing is an important simulation tool in applications where fluorescence is present, e.g. in bio-medical applications and in the design of luminaires and luminescent solar concentrators. A frequently used ray tracing procedure for fluorescence is the ‘dual stage’ approach. In this approach, first, all sources are traced through the system and the rays absorbed in the fluorescent components are stored. Next, the emission from the fluorescent components is traced. This approach does not allow for subsequent re-absorption and re-emission effects in fluorescent materials with a spectral overlap between excitation and emission spectra. In this work, a ‘multi stage’ ray tracing procedure for the simulation of luminescence is presented. Herein, wavelengths are traced from short to long separately and no distinction is made regarding the origin of emission (either a fluorescent component or a source). The presented approach can be easily implemented in existing commercial ray tracing software thus reducing the programming efforts for the new ray tracing algorithm and taking advantage of the strength of the selected ray tracing package concerning the modelling of complex geometrical systems. Both techniques are compared to investigate the influence of the selected ray tracing approach on the efficiency and colour prediction of a remote phosphor LED module.
Proceedings of SPIE | 2016
Paula Acuña; António Correia; Jana Ryckaert; Youri Meuret; Geert Deconinck; Peter Hanselaer
Although the remote phosphor technology outperforms the conformal phosphor technology for mid-power applications, one of the limiting factors is the amount of phosphor required and its impact on the total cost. Besides, an important loss mechanisms in remote phosphor LED technology is the re-absorption of converted light. An obvious solution to this issue is enabling a light path for the converted light, such that further interactions with the phosphor element are avoided. In order to explore such a configuration, a simulation model of a phosphor element is devised and validated based on experimental data and the application of the inverse adding-doubling method. The resulting configuration, denoted as spot concept, along with a long-pass filter is shown to be a potential solution to reduce the phosphor usage. Since the moderate change in the light extraction ratio when applying the spot concept is partly attributed to the losses in the secondary optics needed to narrow the LED beam, the application of the spot concept configuration with a directional light source such as a laser diode could be a powerful combination for the enhancement of the light extraction ratio.
Optical Engineering | 2016
Paula Acuña; Youri Meuret; Geert Deconinck; Peter Hanselaer
Although remote phosphor technology outperforms conformal phosphor technology for midpower applications, one of the limiting factors due to its impact on the total cost is the amount of phosphor required. Furthermore, an important loss mechanism in remote phosphor light-emitting diode (LED) technology is the reabsorption of recycled, downconverted light by the phosphor. An obvious solution to this issue is to enable a light path for the converted light, such that further interactions with the phosphor element are avoided. We propose a spot phosphor concept to achieve this goal. To explore this configuration, a simulation model of a phosphor element is devised and validated. The optical input parameters are based on experimental data and the application of the inverse adding-doubling method. The resulting configuration, along with a long-pass filter, is shown to be a potential solution for reduction of phosphor usage. The moderate decrease in the light extraction ratio (LER) when applying the spot concept is partly attributed to the losses in the secondary optics needed to narrow the LED beam; the combination of the spot concept configuration with a directional light source such as a laser diode is shown to be a powerful combination for the enhancement of the LER.
Archive | 2014
Peter Hanselaer; Paula Acuña; Claudia Sandoval; Elisa M. Colombo; José Sandoval
Proceedings of the 12th Pan American Conference on Lighting | 2014
Paula Acuña; Jesús M. Quintero; Daniel Losada; Frédéric Leloup; Peter Hanselaer
Proceedings of the 18th Annual Symposium of the IEEE Photonics Society Benelux Chapter | 2013
Paula Acuña; Sven Leyre; Jan Audenaert; Geert Deconinck; Youri Meuret; Peter Hanselaer
Proceedings of the 12th Pan American Conference on Lighting | 2013
Paula Acuña; Geert Deconinck; Peter Hanselaer