Diffractive optical elements with continuous relief fabricated by focused ion beam for monomode fiber coupling

Area of Science:

• Optics and Photonics
• Microfabrication Technologies
• Optical Engineering

Background:

• Diffractive optical elements (DOEs) are crucial for advanced optical systems, including fiber coupling.
• Traditional fabrication methods for DOEs can be complex and costly.
• Efficient fiber coupling is essential for telecommunications and optical sensing.

Purpose of the Study:

• To design, microfabricate, and test continuous relief diffractive optical elements (DOEs) for fiber coupling applications.
• To investigate the feasibility of using focused ion beam (FIB) technology for DOE fabrication.
• To compare the performance of FIB-fabricated DOEs with those made by other methods.

Main Methods:

• Microfabrication of DOEs using focused Ga+ ion beam (FIB) milling at 50 kV acceleration voltage.
• Design of DOEs with continuous relief structures, including three and six annulus configurations.
• Optical performance testing, focusing on coupling efficiency and comparison with conventional systems.

Main Results:

• Successful fabrication of DOEs with diameters as small as 50 mm using FIB technology.
• Achieved a coupling efficiency of -1.25 dB (75%) for the tested fiber coupling system.
• FIB-fabricated DOEs demonstrated superior performance compared to conventional plano-convex lens systems, including simplicity, shorter focal length, lower cost, and higher efficiency.

Conclusions:

• Focused ion beam (FIB) technology is a viable and effective method for microfabricating continuous relief diffractive optical elements (DOEs).
• The developed DOE-based fiber coupling system meets application requirements with high coupling efficiency.
• FIB-manufactured DOEs present a practical and advantageous alternative to conventional fiber coupling solutions.