Figure 3.

(a) 3D printing of a complex part in the experimental set-up. (b) Examples of printed and sintered silica glass parts. (c) SEM image of the printed micro-toroid optical resonator (scale bar, 10 μm); inset: optical image from the top. (d) Photoluminescence of Er³⁺-, Eu³⁺-, Tm³⁺-, Nd³⁺-, and Yb³⁺-doped and Er³⁺/Yb³⁺ (1:1)-co-doped silica crystal in the visible to near-infrared range; inset: the Er³⁺-doped micro-toroid optical resonator under 495 nm (left) and 592 nm (right) excitation and observed at 519 nm (left) and 614 nm (right) using a fluorescence microscope. (a,b) Reprinted with permission from ref. [56] © The Optical Society. (c,d) Reprinted with permission from ref. [57].