Photonic Origami of Silica on a Silicon Chip with Microresonators and Concave Mirrors
3D printing of high-quality silica photonic structures is particularly challenging, as surface roughness at the nanoscale can severely degrade optical performance through scattering losses. Here, we develop a technique to fold ultrasmooth silica on silicon chips into such desired 3D structures. A laser-induced, surface-tension-driven method achieves folding with 20 nm alignment accuracy, enabling origami-like polylines and helices with integrated 0.5 nm-smooth photonic devices. The technique allows for the fabrication of record length-to-thickness ratio structures, incorporating concave micromirrors with numerical aperture of 0.41, and microresonators with quality factors exceeding ${8 \times 10^6}$. This on-chip silica origami approach offers a pathway to transform planar electro-opto-mechanical circuits into high-quality 3D configurations.