Now, Innem Reddy, Andrea Bertoncini and Carlo Liberale from KAUST have experimentally demonstrated that a custom-engineered optical fiber can do the job and generate a particular Bessel beam on demand.
"Generating Bessel beams using traditional techniques involves space-consuming, expensive optical elements that require precise alignment," explains Reddy, a Ph.D. student in the group. "By opting for a fiber-based solution, we can obtain a compact Bessel beam generator that is pre-aligned and can deliver these beams even in remote and confined spaces, such as endoscopic applications."
"In particular, the fiber-based generation of Bessel beams allows innovative applications, such as minimally invasive endoscopic probes, optical coherence tomography, fiber-based optical trapping and manipulation of microscopic particles."
The team’s fiber is a masterpiece of custom engineering. They use a technique called two-photon lithography (TPL), which enables 3D printing of intricate optical structures to fabricate special beam-shaping elements directly onto the tip of a single-mode optical fiber. Their design has three segments that, collectively, efficiently align and transform a conventional Gaussian beam into an annular beam and then, finally, a Bessel beam of the desired order and OAM value.
The work is the latest triumph in a research program that intends to leverage the potential of the TPL technique, where light is used to “write” fine optical structures by solidifying a photoresist.
The team has already used TPL to customize fibers in other ways, including the creation of polarization beam splitters, microlens assemblies and optical tweezers. "Fabricating ever more sophisticated optical devices on the end of optical fibers to empower them to deliver complex functionalities is one of the main research directions of our group," commented Liberale.
COMPAMED-tradefair.com; Source: KAUST - King Abdullah University of Science and Technology
