Abstract
The flat endface of an optical fiber tip is an emerging light-coupled microscopic platform that combines fiber optics with planar micro- and nanotechnologies. Since different materials and structures are integrated onto the endfaces, optical fiber tip devices have miniature sizes, diverse integrated functions, and low insertion losses, making them suitable for all-optical networks. In recent decades, the increasing demand for multifunctional optical fibers has created opportunities to develop various structures on fiber tips. Meanwhile, the unconventional shape of optical fibers presents challenges involving the adaptation of standard planar micro- and nanostructure preparation strategies for fiber tips. In this context, researchers are committed to exploring and optimizing fiber tip manufacturing techniques, thereby paving the way for future integrated all-fiber devices with multifunctional applications. First, we present a broad overview of current fabrication technologies, classified as “top-down,” “bottom-up,” and “material transfer” methods, for patterning optical fiber tips. Next, we review typical structures integrated on fiber tips and their known and potential applications, categorized with respect to functional structure configurations, including “optical functionalization” and “electrical integration.” Finally, we discuss the prospects for future opportunities involving multifunctional integrated fiber tips.
Highlights
Waveguide integration includes the integration of functional materials on the outer cylindrical surface of optical fibers, and the function performed within the fiber [e.g., fiber Bragg gratings[19] and holey structures characteristic of photonic crystal (PC) fibers20]
The direct homothetic preform-to-fiber co-drawing method can produce microstructured “multimaterial fibers” combined with a variety of materials with disparate electrical, optical, and mechanical properties by thermal drawing. This method could be applied to a wide range of polymers, glasses, polymer composites, metals, semiconductors, and dielectrics, which greatly improves the scope of applications for optical fibers.[1,2,3,4,5,6,7,8,9,10,11,12,27,28,29,30]
While the fs laser etching process is generally faster and cheaper than those based on focused ion beam (FIB) milling, the processing accuracy is challenging for further applications
Summary
Waveguide integration includes the integration of functional materials on the outer cylindrical surface of optical fibers (such as microfibers,[13,14] unclad fibers,[15,16] and D-shaped fibers15,17,18), and the function performed within the fiber [e.g., fiber Bragg gratings[19] and holey structures characteristic of photonic crystal (PC) fibers20] These devices achieve light–matter interactions over long distances and large areas, they often suffer from certain drawbacks such as large device size, high insertion. There have been several review papers on LOF technology, which have provided a timely overview on many aspects ranging from materials and mechanisms to fabrication techniques as well as device configuration designs, with the aim of realizing integrated and miniaturized all-fiber systems.[21,22,23,24,25,26] As the research continues, the multifunctional fiber tips have broader application prospects and get closer to practical applications.
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