Recently, the Infrared Optical Materials Research Center of Shanghai Institute of Optical Machinery (SIOM), Chinese Academy of Sciences (CAS), has made progress in the research of 3D printing of transparent ceramics for laser illumination - the work has realized the 3D printing of transparent ceramics for laser illumination through Digital Light Processing Printing (DLP), which breaks through the limitations of the traditional ceramic molding process. The results were published in the journal "Ceramics International" (Ceramics International).
LED lighting has the advantages of energy saving, low pollution, high efficiency and long life, but the efficiency will drop after exceeding a certain current. Laser lighting systems are able to achieve high output efficiencies (100-1000 times that of LEDs) at higher power densities, allowing laser-driven lighting systems to provide advantages for future solid-state lighting, such as high brightness, compact size and directional illumination. However, the laser-driven solid-state lighting devices for the optical structure of this system are very complex, and 3D printing becomes a powerful solution.
(a) Schematic of DLP 3D printed transparent ceramic blanks; photographs of printed LuAG:Ce ceramic blanks: (b) honeycomb, (c) minimal surface, (d) superhemisphere, and (e) superhemisphere of different sizes. (f) Schematic of the sintering process of 3D printed LTC; (g) laser illumination device; (h) polished 3D printed LTC placed on "SIOM" letters in daylight; (i) light transmittance spectra; and (j) sintered super-hemispherical 3D printed LTC encapsulated in an LD lighting chip.
DLP is a photopolymerization additive manufacturing technology that uses a digital projector to cure ink layer by layer to create objects with complex shapes. It can cure an entire layer at the same time, thus enabling rapid production. It also supports high-resolution printing, allowing the creation of complex and detailed objects.
3D printing of transparent ceramics for laser-driven SSL has not previously been explored. In this study, researchers at the Shanghai Institute of Optics and Mechanics (SIOM) developed light-curing ceramic inks for DLP for the fabrication of laser-driven illuminated cerium-activated lutetium-aluminum garnet (LuAG:Ce) light-emitting transparent ceramic components with high printing resolution. The ink for DLP printing has a solid content of up to 50 vol% and excellent shear thinning properties. The study introduced luminescent dyes into the DLP inks to reduce the over-curing width effect caused by the scattering of UV light by the ceramic powders. In addition, the researchers further enhanced the strength of the raw blanks by adding a pre-sintering step after the degreasing process, an assisted two-step sintering method - the 3D printed ceramic components sintered to a finished relative density of 96.4% and exhibited excellent light transmission (~40%).
The final experiment shows that the application of LuAG:Ce LTCs 3D printing technology with free geometry design and high laser fluence threshold provides a more efficient and reliable solution for high-power laser-driven lighting.
