Coupling-sensitivity comparison of hemispheric and hyperbolic microlenses

Area of Science:

• Optics and Photonics
• Semiconductor Lasers
• Fiber Optics

Background:

• Efficient coupling between semiconductor lasers and single-mode fibers is crucial for optical communication systems.
• Hemispheric microlenses are commonly used, but hyperbolic microlenses offer potential for higher optical power coupling.

Purpose of the Study:

• To investigate the impact of translational and angular misalignments on semiconductor laser-fiber coupling using hyperbolic and hemispheric microlenses.
• To determine the sensitivity of hyperbolic microlenses to positional and angular deviations and assess their potential for enhanced coupling.

Main Methods:

• Coupling efficiency measurements were performed for semiconductor laser-fiber systems utilizing both hemispheric and hyperbolic microlenses.
• Translational displacements and angular misalignments were systematically varied to quantify their effects on optical power transfer.
• The performance of hyperbolic microlenses was compared against hemispheric lenses under identical misalignment conditions.

Main Results:

• Hyperbolic microlenses demonstrated a typical 2 dB higher optical power coupling efficiency compared to hemispheric lenses.
• Hyperbolic lenses exhibited increased sensitivity to translational offsets but reduced sensitivity to angular misalignments.
• A power penalty of 0.5 dB was observed for hyperbolic microlenses with angular misalignments up to 10 degrees.

Conclusions:

• Hyperbolic microlenses can achieve permanently increased coupling efficiency if the laser package maintains lens position within a 1.6-micrometer tolerance.
• The enhanced coupling benefits of hyperbolic microlenses are achievable with significant angular misalignment tolerance, making them suitable for specific applications.