LASER DIRECT WRITING 3D PRINTING OF LUMINESCENT YAG:Ce MICROSTRUCTURES

A. Harnik¹, R. Virkėtis², D. Dapšys¹, D. Ladika¹, G. Merkininkaitė², S. Šakirzanovas², M. Malinauskas¹

¹ Laser Research Center, Faculty of Physics, Vilnius University, Saulėtekio Ave. 10, LT- 10223, Vilnius, Lithuania

² Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, LT- 03225, Naugarduko Str. 24, Vilnius, Lithuania

[email protected]

Yttrium aliuminium garnet (YAG) has been a laser gain medium for over 60 years [1]. Czochralski synthesis method has been used as the primary production method of YAG monocrystals [2]. While polycrystalline YAG has a higher number of synthesis methods available for its production [3,4], none of them are suitable for the fabrication of complex 3D YAG microstructures. This work aims to show that two-photon polymerization laser 3D printing [5] can produce polycrystalline 3D luminescent YAG:Ce microstructures via the post-processing calcination step [6,7].

YAG and YAG:Ce precursor 3D objects were produced by a Laser Nanofactory (UAB Femtika) femtosecond laser lithography workstation and using two-photon polymerization 3D printing method for enhanced resolution. 517 nm irradiation wavelength laser of 144 fs pulses was used for the fabrication of 3D microstructures. To study and determine the most optimal production parameters for these materials, 3D arrays of woodpile structures were printed by changing exposure power (intensity) and fabrication time (scanning velocity). After the fabrication, polymerized YAG/YAG:Ce precursor samples were immersed in ethanol to dissolve unpolymerized resin. Afterward, samples were heated first at 800 °C to remove all of the organic matter and later at 1600 °C to produce pure YAG/YAG:Ce. The temperature necessary for the first heating step was determined using the thermogravimetric analysis method. The purity of the calcinated YAG/YAG:Ce samples was also estimated using the single crystal X-ray diffraction analysis method. This was done by obtaining X-ray diffraction data - Debye Scherrer rings, and integrating that data using Bruker Apex 3 software. Finally, luminescence measurements of YAG:Ce were carried out, showing the dependence of Ce concentration on luminescence intensity. This research has been carried out in the framework of the "Universities‘ Excellence Initiative" program by the Ministry of Education, Science and Sports of the Republic of Lithuania under the agreement with the Research Council of Lithuania (project No. S-A-UEI-23-6) and was funded by Vilnius University Research Promotion Fund (project No. MSF-JM-10/2024).

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