  Integration of complex photonic structures onto optical fiber facets enables
powerful platforms with unprecedented optical functionalities. Conventional
nanofabrication technologies, however, do not permit viable integration of
complex photonic devices onto optical fibers owing to their low throughput and
high cost. In this paper we report the fabrication of a three dimensional
structure achieved by direct Nanoimprint Lithography on the facet of an optical
fiber. Nanoimprint processes and tools were specifically developed to enable a
high lithographic accuracy and coaxial alignment of the optical device with
respect to the fiber core. To demonstrate the capability of this new approach,
a 3D beam splitter has been designed, imprinted and optically characterized.
Scanning electron microscopy and optical measurements confirmed the excellent
lithographic capabilities of the proposed approach as well as the desired
optical performance of the imprinted structure. The inexpensive solution
presented here should enable advancements in areas such as integrated optics
and sensing, achieving enhanced portability and versatility of fiber optic
components.
