A team of researchers has developed a means of 3D printing tiny lenses for use on optical fibers. The printed lens fits onto the end of an optical fiber and focuses the different wavelengths into a point, reducing optical errors that result from the use of traditional lenses.
Read on to know more.
Aberrations
The multinational research team, with the collaboration of Leibniz Institute of Photonic Technology (Leibniz IPHT) successfully utilized two-photon polymerisation nano-scale printing to manufacture the meta-lens, which has a diameter of just 100 microns.
Optical lenses of this type are traditionally used for optical focusing and imaging for medical applications (such as endoscopy) but suffer from strong optical aberration, especially at such small scales.
This chromatic aberration occurs due to different wavelengths refracting differently as they hit a lens. Generally speaking, in transparent materials the refractive index of the lens elements decrease as the light wavelengths increase.
As the focal length of the lens is related to the refractive index, the result is that the lens cannot focus all of the entire spectrum into a single point.
This effectively leads to a shift in the focal point and blurring over the different wavelengths. Achromatic lenses can reduce these aberrations.
And that’s exactly what the printed lens does. The tiny lens is capable of performing achromatic and polarization-insensitive focusing across the entire near-infrared telecommunication wavelength band ranging from 1.25 to 1.65 µm. This covers the entire wavelength range of commercially available fibers.
“For ideal light shaping and achromatic focusing, we realized an ultrathin polymer-based lens, which consists of a complex design of geometric structures in the form of nanopillars,” said Markus Schmidt, head of the Fiber Photonics Department at Leibniz IPHT.
“This structure was printed directly on the tip of a 3D-printed hollow tower structure on one of the end faces of a commercial optical fiber. In this way, optical fibers can be functionalized in such a way that light can be focused very efficiently on a focal point and images with high resolution can be generated.”
Meta-optics
Meta-optics allow the arbitrary shaping of light by using ultrathin metasurfaces which permits the fabrication of optical devices with super-enhanced performance. A meta-lens not only allows for diffraction-limited light focusing, but also for a correction of possible aberrations without using additional optical elements.
“Since the developed nanostructured meta-lens is extremely small and flat, a fiber optic design with achromatic optics at the top offers the potential to further advance miniaturized and flexible endoscopic imaging systems based on fiber technology and to enable even more gentle minimally invasive examinations,” explained Schmidt.
That’s good news for sure. You want your endoscopic exams to be as minimally invasive as possible.
Not only does the meta-lens promise to improve endoscopy, but the tech could find applications in microscopy and sensor design also.
The paper, titled “An achromatic metafiber for focusing and imaging across the entire telecommunication range” has been published in Nature Communications, and can be accessed at this link.
