Microlenses for coupling single-mode fibers to single-mode thin-film waveguides

Area of Science:

• Optics and Photonics
• Materials Science

Background:

• Single-mode optical fibers are crucial for telecommunications and sensing.
• Efficiently coupling light from optical fibers into other components is a key challenge.
• Existing microlens fabrication methods can be complex and costly.

Purpose of the Study:

• To develop a simple and effective method for fabricating microlenses on single-mode optical fibers.
• To demonstrate the beam-shaping capabilities of these novel microlenses.
• To investigate the impact of microlens fabrication on optical coupling efficiency.

Main Methods:

• A negative photoresist was used to form microlenses on fiber ends.
• A He-Ne laser (0.1 mW) was guided through the fiber core during photoresist dipping.
• The number of dipping cycles controlled the final microlens dimensions and waist reduction.

Main Results:

• Microlenses were successfully fabricated without developing or rinsing steps.
• The fabricated microlenses transformed the fiber's near-Gaussian output beam into a new near-Gaussian beam.
• A significant reduction in beam waist diameter was achieved, controllable by the dipping process.
• Improved coupling into single-mode optical waveguides was demonstrated.

Conclusions:

• The laser-assisted photoresist dipping method provides a straightforward approach to producing optical fiber microlenses.
• These microlenses effectively modify the output beam characteristics for enhanced optical coupling.
• The technique offers a cost-effective and efficient solution for fiber optic component integration.