Fabrication of antireflection subwavelength gratings at the tips of optical fibers using UV nanoimprint lithography

Antireflection (AR) layers at the tips of optical fibers are indispensable in high efficiency and low noise applications. We realized the AR structures with two-dimensional binary subwavelength gratings (SWGs) at the tips of optical fibers by using a dedicated UV nanoimprint machine. Using this technique, ideal AR structures with desired refractive indices can be realized at low cost in principle. The SWG with the period of 700 nm was fabricated at the tip of a single-mode optical fiber for optical communications system. The reflectance was decreased to less than 0.27% at measured wavelengths between 1460 nm and 1580 nm.