High refractive index Fresnel lens on a fiber fabricated by nanoimprint lithography for immersion applications

In this Letter, we present a Fresnel lens fabricated on the end of an optical fiber. The lens is fabricated using nano-imprint lithography of a functional high refractive index material, which is suitable for mass production. The main advantage of the presented Fresnel lens compared to a conventional fiber lens is its high refractive index (n = 1.68), which enables efficient light focusing even inside other media, such as water or an adhesive. Measurement of the lens performance in an immersion liquid (n = 1.51) shows a near diffraction limited focal spot of 810 nm in diameter at the 1/e(2) intensity level for a wavelength of 660 nm. Applications of such fiber lenses include integrated optics, optical trapping, and fiber probes. (C) 2016 Optical Society of America