凹陷包层波导是一种新型波导,其折射率未变化的波导芯被数量众多的折射率变低的轨迹包围,具有截面形状和大小可以灵活调控的优点。凹陷包层波导芯区保留了材料原本的性质,可以传播横电和横磁两种偏振模式,在集成光子学领域具有重要的发展潜力。利用飞秒激光三维微纳加工技术,可以在多种玻璃和晶体材料中制备凹陷包层波导。除了通过平移和螺旋扫描进行制备,还可以利用焦场整形技术实现快速制备。综述了凹陷包层波导的飞秒激光加工进展及其在波导激光器、频率转换、温度传感、波导光栅滤波器和集成光子学器件等方面的应用。

Depressed cladding waveguide is a new kind of waveguide whose unmodified core is surrounded by numerous lower refractive index tracks. It is flexible to manipulate their shapes and sizes of the cross sections while the original properties of the material are well preserved in the region of guiding core, so the waveguides can support both transverse electric and transverse magnetic polarization modes and they have an important application prospect in integrated photonics. By using femtosecond laser writing technique, the depressed cladding waveguides have been fabricated in various glass and crystal materials. The process is completed by the translational and helical focus moving, and the fast fabrication can be realized through the focal field engineering. In this review, we summarize the development of laser direct writing of depressed cladding waveguides and their wide applications to waveguide lasing, frequency conversion, temperature sensing, waveguide grating filters and integrated photonic devices, and so on.