MIT engineers recently designed a tunable “metalens” that can zero in on objects at multiple depths. The lens, constructed from a transparent “phase-changing” material capable of rearranging its atomic structure after heating, is capable of transforming how its material interacts with light.
The invention is a breakthrough in the field of photonics. Traditionally, changing the focus of a microscope or telescope to see at multiple scales meant having to physically move the lens, which required extra mechanical parts. However, metalens don’t need to be moved to change focus.
The engineers carved carefully patterned structures into the material’s surface, which form a “metasurface” that refracts light in different ways.
When the material’s property shifts, the optical function of the metasurface changes. For example, at room temperature, the metasurface focuses light to produce a crisp image of an object at a specific distance. When heat is applied, the material transforms its atomic structure. The metasurface then shifts light to focus on an object that’s further away. In other words, the metalens can change focus without the need for extra mechanical parts in the device.
This innovative lens could allow for the development of more flexible optical devices. A few potential use cases include a mini heat scope for drones, super-compact thermal cell phone cameras, and low-profile goggles for night vision.
“Our result shows that our ultrathin tunable lens, without moving parts, can achieve aberration-free imaging of overlapping objects positioned at different depths, rivaling traditional, bulky optical systems,” Tian Gu, a research scientist in MIT’s Materials Research Laboratory, told MIT News.
Photonics Researchers Use Finite Element Method to Test Devices with Metasurfaces
Increasingly, metasurfaces are becoming popular materials for use in optical applications. Due to their small size and unique properties, however, metasurfaces can be challenging to design.
“Metasurfaces are currently fabricated by highly demanding procedures that typically involve deposition of a transparent dielectric, followed by lithographic patterning, additional depositions, etching, and so on,” wrote researchers from Chalmers University of Technology in Sweden in a paper published in ACS Photonics. Their study focuses on new methods for creating phase-gradient metasurfaces that can improve the processing of metasurfaces.
Last year, photonics researchers used the Finite Element Method (FEM) to test a number of devices equipped with metasurfaces. As discussed in a previous post, FEM is a numerical solution that breaks down a much larger, complex problem into a series of smaller ones (“finite elements”) in order to make the overall problem easier to examine. This equation is then used to create a digital simulation (known as the finite element analysis), which gives engineers a more detailed look into the design and how its various elements work together.
With researchers discovering more and more breakthroughs in the field of photonics, FEM is quickly becoming a useful tool for aiding their designs.
Finite Element Method (FEM) for Photonics
Learn how FEM can be used to model and simulate photonic components/devices and analyze how they will behave in response to various outside influences. The Finite Element Method for Photonics course program provides a comprehensive and up-to-date account of FEM in photonics devices, with an emphasis on practical, problem-solving applications and real-world examples. Engineers will gain an understanding of how mathematical concepts translate to computer code finite element-based methods after completing this program.
Connect with an IEEE Content Specialist today to learn how to get access to this program for your organization.
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(24 February 2021). Phase-changing metalens focuses without moving. Optics.org.
Chu, Jennifer. (22 February 2021). New “metalens” shifts focus without tilting or moving. MIT Materials Research Laboratory.
(16 June 2020). Metasurfaces allow ultra-thin camera lenses. Optics.org.
Andren, Daniel , Käll, Mikael, Martínez-Llinàs, Jade, Tassin, Philippe, Verre, Ruggero. (2020). Large-Scale Metasurfaces Made by an Exposed Resist. ACS Photonics.