Fabrication of antireflective subwavelength-grating structures on optical fiber end faces using nanoimprinting technique

We proposed optical fibers with antireflective subwavelength-grating (SWG) structures and their fabrication method using a nanoimprinting technique. Antireflective coatings on optical fiber end faces are essential optical components to couple efficiently the light with the optical fiber. Because commercially available nanoimprinting machines are designed to press two plates set parallel to each other, it is difficult to set a flexible and long optical fiber in the nanoimprinting machine, and to press the optical fiber end face to a mold. In this paper, we developed a novel nanoimprinting machine to press an optical fiber end face to a plate of mold. Using the developed machine, antireflective SWGs with the periods of 150 nm were fabricated on the end faces of plastic optical fibers. A silicon SWG with 150 nm period and 348 nm height was used as a mold. Reflectance and transmittance of the SWGs were measured and compared with that of a flat end face of a plastic optical fiber.