• Advanced Photonics
  • Vol. 3, Issue 2, 024002 (2021)
Dezhi Tan1、*, Zhuo Wang1, Beibei Xu1, and Jianrong Qiu1、2、*
Author Affiliations
  • 1Zhejiang University, College of Optical Science and Engineering, State Key Laboratory of Modern Optical Instrumentation, Hangzhou, China
  • 2Chinese Academy of Sciences, CAS Center for Excellence in Ultra-Intense Laser Science, Shanghai, China
  • show less


    Integrated photonics is attracting considerable attention and has found many applications in both classical and quantum optics, fulfilling the requirements for the ever-growing complexity in modern optical experiments and big data communication. Femtosecond (fs) laser direct writing (FLDW) is an acknowledged technique for producing waveguides (WGs) in transparent glass that have been used to construct complex integrated photonic devices. FLDW possesses unique features, such as three-dimensional fabrication geometry, rapid prototyping, and single step fabrication, which are important for integrated communication devices and quantum photonic and astrophotonic technologies. To fully take advantage of FLDW, considerable efforts have been made to produce WGs over a large depth with low propagation loss, coupling loss, bend loss, and highly symmetrical mode field. We summarize the improved techniques as well as the mechanisms for writing high-performance WGs with controllable morphology of cross-section, highly symmetrical mode field, low loss, and high processing uniformity and efficiency, and discuss the recent progress of WGs in photonic integrated devices for communication, topological physics, quantum information processing, and astrophotonics. Prospective challenges and future research directions in this field are also pointed out.

    1 Introduction

    Photonic integrated circuits have shown the potential to allow integrating passive and active optical components on one chip in a scalable manner and have been identified to support a plethora of applications, such as data communication, sensing, astrophotonics, quantum information processing, and national security.14 Photonic circuits are indispensable components in modern optical communication networks and lie at the heart of integrated photonic devices. Currently, to this end, one of the biggest challenges in integrated photonics is establishing a general and flexible method to produce photonic circuits with low loss, high integration density, and high tunability. The unique feature of 3D fabrication geometry promises femtosecond laser direct writing (FLDW) as an on-demand solution to these requirements.