Laser Printing of Large-Area Conformal 3D photonic Circuits in Glass

Photonic integrated circuits (PICs) are iterating on electronic ones to enable higher-speed parallel computing while meeting the growing demands for energy efficiency in big-data processing. However, manufacturing multi-layered and 3D PICs remains challenging based on conventional planar lithography. Here, a rapid prototyping technique is delineated to configure large-area and 3D PIC in glass based on laser-direct written optical waveguides by employing femtosecond cylindrically polarized vortex laser beams. The vortex laser beam is mathematically rotationally invariant and capable of conformally transforming waveguide cross-sections at arbitrary bending angles of 0-90 degrees and across a large depth change. Based on this approach, a one-layer 12-core waveguide circuit with a variable cross-section (diameter 5-11.5 mu m) while maintaining a high mode ellipticity >0.974, as well as a more complex three-layer 36-core connector in which the waveguide dives continuously from 50 mu m to 550 mu m with a small loss difference of <0.1 dB is demonstrated. This work offers a pathway for 3D imprinting of large-area photonic circuits in glass and other transparent materials, which has potential applications in high-efficiency photonic computing, multidimensional quantum networks, and 3D optics topology.