Microlenses for coupling junction lasers to optical fibers

Area of Science:

• Optoelectronics
• Nanofabrication
• Fiber Optics

Background:

• Efficient coupling of laser beams into single-mode optical fibers is crucial for optical communication systems.
• Astigmatic beams from GaAs junction lasers present challenges for high-efficiency fiber coupling.
• Existing microlens fabrication methods have limitations in precision and scalability.

Purpose of the Study:

• To develop and characterize novel microscopic lenses for enhanced coupling of astigmatic laser beams into optical fibers.
• To investigate the efficiency improvements achieved by these new microlenses.
• To explore a new photolithographic technique for fabricating high-precision microlenses.

Main Methods:

• Fabrication of hemispherical and hemicylindrical microlenses on optical fiber surfaces using a novel photolithographic technique.
• Utilized commercially available negative photoresist transparent at infrared (IR) laser wavelengths.
• Characterization of microlens geometry and surface smoothness using scanning electron photomicrography.

Main Results:

• Achieved a quadrupled increase in the efficiency of coupling astigmatic beams from GaAs junction lasers into 4-microm cores of single-mode fibers.
• Successfully fabricated microlenses with diameters ranging from 4 microm to 10 microm.
• Observed remarkably smooth geometrical profiles of the photoresist lenses, despite their sub-10-microm dimensions.

Conclusions:

• The novel photolithographic technique enables the efficient fabrication of high-precision microscopic lenses for optical fiber applications.
• These microlenses significantly enhance the coupling efficiency of laser beams, particularly astigmatic beams, into single-mode fibers.
• The developed microlenses represent a promising advancement for improving performance in fiber optic communication and related technologies.