Tomáš got his Master degree of Material chemistry and material engineering from Institute of Chemistry and Technology Prague – specifically Materials in electronics studying high electron mobility graphene layers prepared via high temperature methods on silicon carbide single crystalline materials. Since 2013 Tomáš is a member of Material Research Department in CRYTUR as a research engineer. The main topics are monocrystalline luminophores in advanced LED applications when developing the luminophores according to customer application and implementation of these products into manufacturing process. Other topic is searching of new promising monocrystalline materials and last but not least is a patent area of luminophores.
Monocrystalline Luminophores for High Power Illumination (Laser)
Single crystals of composition (Lu,Y,Gd)AG:Ce3+ were introduced as a new category of luminophores (also called “phosphors”) for solid state lighting (SSL) recently. Novel applications are still under development and reflects rising efficiency and light power density from blue SSL sources (LED/light emitting diodes and LD/laser diodes), this nevertheless create new demands to material of light convertors. Next to traditional phosphors based on oxidic garnets new and alternative materials are now discussed as well.
Single crystal materials open completely new area of luminophore material engineering where phosphor is defined by exact absorption coefficient and by others optical parameters which can be tuned continuously directly to application request. An optical isotropy and absence of any internal scattering in combination with high index of refraction predetermines such a material for using as a fully valuable optical elements incorporated as a part of optics of lighting modules. Smart deposition of reflective and antireflective coatings in most of cases can cause another boost of the performance. In comparison with other types of luminophores, single crystal offers better thermal conductivity (up to 12 W.m-1.K-1) and practically unlimited lifetime.
An ideal light source (for automotive headlamps, searchlights or projectors), with as small light emitting area as possible, can be obtained as a combination of powerful blue laser and the best performing luminophore. Such a luminophore can be steadily operated at temperature over 250°C. This has destructing effect on common phosphors materials which are combined with binders as a silicone or resins. In such a case only two types of luminophore materials can withstand these operation conditions – polycrystalline optoceramics and single crystal. Thermo-management of luminophore component is in all cases critical part of any application and possible approaches are discussed.
Most promising solution for high power laser lightening is represented by remote phosphor excitation in reflectance arrangement. Advantages of such a design as a luminophore thermo-management, light enhancement techniques, color homogeneity and suppression of speckle pattern are discussed more deeply.