Efficient input and output fiber coupling to a photonic crystal waveguide

Citation

Barclay, P. E., Srinivasan, K., Borselli, M., & Painter, O. (2021). Efficient input and output fiber coupling to a photonic crystal waveguide. Department of Applied Physics, California Institute of Technology, Pasadena, California 91125.

Keword 

• photonic crystal waveguide
• fiber taper
• evanescent coupling
• coupling efficiency
• high reflectivity mirror
• contradirectional coupling

Brief

A study that reflects light off the end of a photonic crystal waveguide coupled to a fiber taper shows that this coupling scheme is almost perfectly efficient. 

Summary

The article investigates the efficiency of coupling light between a silica optical fiber taper and a silicon photonic crystal waveguide (PCWG) using an evanescent coupling technique. The authors use a high reflectivity mirror at the end of the PCWG to reflect light back into the fiber. By measuring the amount of light coupled back into the fiber, the authors determine a lower bound on the coupling efficiency of 94%.
The authors designed the PCWG with a "grade in hole radius" to enable efficient power transfer between the fiber taper and the waveguide. To improve the accuracy of their measurements, the authors engineered the waveguide terminations to have either high or low broadband reflectivities.
Through careful measurements and modeling, the authors found that the high reflectivity PCWG end-mirror was not perfect, limiting the maximum reflected power. However, their results still demonstrate a high coupling efficiency of approximately 97%, making this coupling scheme promising for integrating photonic crystal devices with fiber optics.

Origin: https://www.semanticscholar.org/reader/d1db56eb80feef65d323c206b56b959c1bdcc218