Researchers have developed new 3D printed microlenses with adjustable indices of refraction – a property that gives them highly specialized light focusing capabilities. This advance will improve imaging, computing, and communications by significantly increasing the data conductivity of computer chips and other optical systems, the researchers said.
The study, led by the University of Illinois Urbana-Champaign researchers Paul Braun and Lynford Goddard, is the first to demonstrate the ability to determine with precision the direction in which light curves and moves through a lens set in the sub-micrometer range.
The results of the study are published in the journal Light: Science and Application Published.
“The ability to manufacture optics with different shapes and optical parameters offers a solution to common problems in optics,” said Braun, who is a professor of materials science and engineering. “In imaging applications, for example, focusing on a specific object often leads to blurred edges. Or, in data transfer applications, higher speeds are desired without sacrificing space on a computer chip. Our new lens manufacturing technology solves these problems in one integrated device.
For the demonstration, the team produced three lenses: a flat lens, the world’s first Lüneburg lens for visible light – a previously unproductive spherical lens with unique focusing properties – and 3D waveguides, which may enable massive data-transfer capabilities.
“A standard lens has a single index of refraction and therefore only a single path that light can travel through the lens,” said Goddard, professor of electrical and computer engineering. “By being able to control the internal index of refraction and the shape of the lens during manufacture, we have two independent ways to bend the light within a single lens.
In the lab, the team uses a process called direct laser writing to make the lenses. A laser solidifies liquid polymers and forms small geometric optical structures that are up to 100 times smaller than a human hair. Direct laser writing has been used in the past to make other microlenses that only had one index of refraction, the researchers said.
“We addressed the refractive index limitations by printing into a nanoporous scaffold substrate,” said Braun. “The framework locks the printed micro-optics in place and enables the production of a 3D system with hanging components.
The researchers suspect that this refractive index control is a result of the polymer curing process. “The amount of polymer that becomes trapped in the pores is controlled by the laser intensity and exposure conditions,” said Braun. “While the optical properties of the polymer itself do not change, the overall index of refraction of the material is controlled as a function of the laser exposure.
The team said they expect their method to have a significant impact on the manufacture of complex optical components and imaging systems and to be useful in the advancement of personal computers.
“A great example of how this development can be applied will be its impact on data transfer within a personal computer,” said Goddard. “Today’s computers use electrical connections to transfer data. However, with the help of a fiber optic cable, data can be sent at a much higher rate because different colors of light can be used to send data in parallel. A major challenge is that conventional waveguides can only be manufactured in a single plane and therefore only a limited number of points can be connected on the chip. By making three-dimensional waveguides, we can drastically improve data routing, transmission speed and energy efficiency.
Reference: “Direct laser writing of lenses and waveguides with volumetric gradient index” by Christian R. Ocier, Corey A. Richards, Daniel A. Bacon-Brown, Qing Ding, Raman Kumar, Tanner J. Garcia, Jorik van de Groep, Jung-Hwan Song, Austin J. Cyphersmith, Andrew Rhode, Andrea N. Perry, Alexander J. Littlefield, Jinlong Zhu, Dajie Xie, Haibo Gao, Jonah F. Messinger, Mark L. Brongersma, Kimani C., Tanner J. Garcia, Tanner J Garcia, Jorik van de Groep Toussaint Jr., Lynford L. Goddard and Paul V. Braun, December 3, 2020, Light: Science and Applications.
DOI: 10.1038/s41377-020-00431-3
The lead authors of the study are Christian Ocier and Corey Richards, graduates of the U. of I.
Braun is the director of the materials research laboratory and a subsidiary of the Beckman Institute of Advanced Science and Technology. Goddard is the director of the Institute for Inclusion, Diversity, Equity and Access at Grainger College of Engineering and is a subsidiary of the Holonyak Micro and Nanotechnology Laboratory in Illinois.
The US Department of Energy, the United States of I., and the National Science Foundation supported this research …
–
