Controllable Photonic Structures on Silicon-on-Insulator Devices Fabricated Using Femtosecond Laser Lithography

The design of micro/nanostructures on silicon-on-insulator (SOI) devices has attracted widespread attention in the science and applications of integrated optics, which, however, are usually restricted by the current manufacturing technologies. Hence, in this paper, we propose a mask-free, one-step femtosecond laser lithography method for efficient fabrication of high-quality controllable planar photonic structures on SOI devices. Subwavelength gratings with high uniformity are flexibly prepared on a SOI wafer, and they can be efficiently extended for large-area fabrication with long-range uniformity. Different from the melt flow mechanism to bulk silicon, the buried SiO₂ layer of the SOI material provides substantial control over the phase change process, thereby achieving local rapid vaporization to form a high-quality structure. The optical properties of the prepared structures are measured experimentally and determined to possess powerful diffraction and light-coupling characteristics. Strikingly, active control of the SOI surface structure morphology, from the grating to the periodic silicon wire structure, can be realized through precision adjustment of the pulse injection volumes. A homogeneous silicon photonic wire is successfully generated on the SOI device, providing an alternative to the preparation of waveguides. This effective femtosecond laser lithography method for fabricating controllable photonic structures on SOI devices is expected to further promote the development of integrated optics.