On-Chip Photonics Integrated Circuits Formed by Three-Dimensional Waveguides for Mode Manipulation

Chip-scale photonics integrated circuits have attracted great attention in optical communications for decades due to their advantages in material compatibility, power consumption, bandwidth, and integrability. We present a comprehensive introduction of mode-manipulating devices based on three dimensional (3D) waveguide circuits, where these devices are fabricated by using optical lithography, femtosecond laser direct writing, or 3D printing based on two-photon absorption methods. We also discuss the future development and applications of the 3D photonic chips, which can find further applications in quantum optics, signal processing, and biosensing, all leveraging mode manipulation.