Fabrication of Cylindrical Microlens by Femtosecond Laser‐Assisted Hydrofluoric Acid Wet Etching of Fused Silica

Abstract

Micro‐optical elements play a key role in various advanced devices, including biomedical, photovoltaic, 3D display, and optical communication devices. As one of the typical micro‐optical elements, cylindrical microlens (CML) can modulate the wavefront phase of the incident light in only one direction. The process methods of CML have been developed and various methods are proposed for CML fabrication. For the simple and versatile fabrication of CML on hard brittle materials, femtosecond laser direct writing combined with hydrofluoric acid (HF) wet etching for removal of laser‐modified regions in fused silica is proposed here for high‐quality CML fabrication. A high‐accuracy CML can be processed by adjusting the HF etching time, femtosecond laser pulse energy, and the position of the laser exposure point. Crossed‐shaped CML can be realized by accurate control of the single laser pulse exposure positions at the intersection in two directions. A series of alphabet‐shaped CML, showing this fabrication method's flexibility is made. The characterization of the CML under a microscope system reveals a good optical focusing ability. The proposed method offers a practical route toward the manufacture of CML on hard brittle materials.

Keywords

• cylindrical microlenses
• femtosecond laser single pulse exposure
• hydrofluoric acid (HF) wet etching
• optical performances