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.
Interested in the course for yourself? Visit the IEEE Learning Network (ILN).
Resources
(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.
The majority of medical, scientific, and industrial applications utilize high-power diode-lasers (HPDLs). Due to the common use of HPDLs, it’s more important than ever to prevent optical and physical malfunctions in high-power laser packages. However, as laser technology has become more advanced, HPDL output power has gotten larger. With it, the waste-heat energy density of a sole diode laser bar has expanded from 200 W/cm2 to more than 600 W/cm2.
Thermal issues often result in failures when heat gets trapped in HPDL packaging. This impacts a number of outcomes, including output power, threshold current, slope efficiency, spectral broadening, wavelength shifts, and device lifetime. However, by designing high-power laser packages using finite-element method (FEM) simulations, potential for failures can be minimized.
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”). This is done 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). It gives engineers a more detailed look into the design and how its various elements work together.
Using FEM to Evaluate the Thermal Performance of High-Power Diode-Lasers
Thermal stress is a major challenge when it comes to HPDLs packaging. For instance, thermal stress often leads to mechanical tension in the diode and transforms the band structure. This changes the characteristics of the diode laser in regards to threshold, wavelength, polarization, and SMILE (near-field nonlinearity along the laser bar). Additionally, induced thermal stress in the laser device might harm the laser chips/bars. Therefore, it may reduce the device’s lifetime.
Recently, Chinese researchers from the Design and Simulation Technology Department at Focuslight Technologies used digital simulations, including FEM. They did this to get an up-close look at how these kinds of potential failures can be avoided.
“The finite-element model (FEM) simulation results show that the compression stress on the laser bar decreases with the increase of copper-tungsten (CuW) submount thickness. This happens as the CuW submount works as a buffer layer and can thus absorb stress,” the researchers wrote in Laser Focus World. “However, the laser bar out-of-plane strain (SMILE value) is approximately zero when the diode-laser array is directly bonded onto the heat sink without a submount. The SMILE value is maximized when the thickness of the CuW submount is increased to 44% of the heat sink. Beyond this point, the SMILE value decreases with increasing CuW submount thickness.”
Additionally, the authors used FEM to determine that adhesion in a corner of a microlens array diffuser was the source of cracking. After they controlled the adhesion in the FEM simulation, they found they reduced stress on the diffuser.
“Easy-to-use FEM methods have been presented for evaluating the thermal performance of HPDLs and the stress distribution in HPDLs. These methods make it much easier to understand the physics of the addressed thermal phenomena. Additionally, they predict their thermal behavior and performance,” they wrote.
Photonics Researchers Are Increasingly Relying on FEM
More and more, photonics researchers are using FEM. In a previous post, we discussed how engineers used FEM to demonstrate the potential for light-based circuits. In another post, we discuss how researchers demonstrated off-chip beam deflection and focusing with guided wave driven metasurfaces on silicon waveguides. This has the potential to transform traditional optics technology. These are just some of the ways researchers are using FEM to revolutionize 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. It emphasizes 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.
Interested in the course for yourself? Visit the IEEE Learning Network (ILN).
Resources
Wang, Jingwei, Fu, Tuanwei, and Liang, Xuejie. (11 November 2020). Simulation and modeling play key roles in high-power diode-laser packaging. Laser Focus World.
Optical lenses are vital components to the manufacturing and labeling of goods. For example, optical lenses are found in electronic devices like smartphones and laptops. They’re also used to make logos and graphics on hardware as well as other kinds of markings commonly found on commercial products and food packaging. These markings are created by high-powered lasers that pass through a series of optical lenses.
Computer simulation technology is important to the development of optical lenses, because it can reduce the number of prototypes needed during the design phase. These simulations give developers valuable insight into how to improve optical lens designs while also saving time.
There are a few simulation methods that can be used to analyze lens designs, from traditional techniques to those that solve all of Maxwell’s equations—a sophisticated set of equations that describe how electric charges and electric currents produce electric and magnetic fields.
Optical lens simulation relies on two categories. The first is design, in which a lens is optimized specifically for a certain function. The second is analysis, which gives a designer insight into what’s happening within the lens.
“Wave Optics” for Design
An example of optical lens design is the process of determining the ideal shape for a lens to direct a laser in a particular way. Typically, the goal of lens design is to reduce abnormalities as much as possible.
Simulations that employ ray-tracing, a process in which rays approximate electromagnetic waves, are often used for design. However, ray-tracing simulations don’t provide the effects of diffraction, which is characterized by light slightly bending as it passes over the edge of an object, so they aren’t 100% effective. In situations where it’s necessary to capture diffraction, “wave-optics” methods are considered ideal. These are computational high-frequency electromagnetics software that rely on a number of general-purpose numerical methods, including the finite-element methods (FEM). 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 simulation (known as the finite element analysis), which gives engineers a more detailed look into the design and how its various elements work together.
Unlike other methods, wave optics can be used for both design and analysis of optical lenses.
“Wave Optics” for Analysis
For optical lens analysis, Maxwell’s equations are necessary to acquire the electromagnetic fields’ complete vector representation. A simulation method known as “full-wave” uses FEM to solve the entire domain of Maxwell’s equations by breaking it down into a mesh. It is then subdivided into smaller elements with a simpler shape.
The full-wave method poses some challenges. For example, the innumerable mesh elements created can be difficult for a typical computer to handle. However, there are formulations to get around this issue.
Full-wave simulations for multicomponent optical systems were once thought impossible, but thanks to these FEM-based methods, the ability to simulate whole optical systems is closer than ever before.
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.
Interested in the course for yourself? Visit the IEEE Learning Network (ILN).
Resources
Mizuyama, Yosuke. (15 September 2020). Full-wave simulation extends the range and depth of lens analysis. Laser Focus World.
Sjodin, Bjorn. (9 November 2017). Wave Optics: Beam-envelope method efficiently analyzes photonic components. Laser Focus World.
The optics and photonics fields are creating groundbreaking applications for astronomy, telecommunications, sensing, chemistry, biomedical research & development.
Recently, researchers from Pennsylvania State University demonstrated how metasurfaces with unparalleled controllability of light may be able to transform traditional optics. To do so, they used a simulation that applied the finite element method (FEM).
As discussed in a previous post, FEM is a numerical solution for a complex problem, which breaks down a much larger problem into a series of smaller ones (“finite elements”), making the overall problem easier to pick apart. This equation is then used to create a simulation (known as the finite element analysis), which gives engineers a more detailed analysis into the design and how its various elements work together.
How Engineers Used FEM to Demonstrate the Potential of Metasurfaces
“Metasurfaces” are thin, two-dimensional metamaterial layers that permit or prevent the propagation of electromagnetic waves in desired directions. They are thought to have enormous potential to transform traditional optics technology.
However, metasurfaces do pose some problems. For instance, metasurfaces depend on the excitation of external light. Because of this, it’s challenging to integrate the layers completely onto a single chip. Conversely, while integrated photonics allows optical components to be packed compactly onto a chip, there’s not enough space to control light.
The Pennsylvania State researchers found a solution: they dressed metasurfaces onto waveguides. These structures can guide waves—including electromagnetic waves. By doing this, they molded guided waves into the free-space modes they desired. The process allowed them to create complex free-space functions, like out-of-plane beam deflection and focusing.
Using FEM simulations, the researchers demonstrated a feasible way to control light on integrated photonics and free-space metasurfaces. The study may represent a path forward for scientists to be able to make multifunctional photonic integrated devices with the ability to easily access free space, allowing for a range of advancements in optical communications.
“We have experimentally demonstrated off-chip beam deflection and focusing using the guided wave driven metasurfaces on silicon waveguides. In addition, two-dimensional (2D) manipulation of free-space light can be realized by placing a 2D array of meta-atoms on a slab waveguide. This technology can enable a wide spectrum of applications ranging from optical communications to LiDAR, as well as miniaturized display technology for virtual reality and augmented reality devices,” the researchers wrote in Science Advances.
This study is just one example of how researchers are using FEM to make breakthroughs in optics and photonics. Another team of researchers recently used FEM to demonstrate a potential new way to develop innovative applications in quantum communications and information processing.
Finite Element Method (FEM) for Photonics
This course program from IEEE Educational Activities, Finite Element Method for Photonics, 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 come away from this program with an understanding of how mathematical concepts translate to computer code finite element-based methods.
Contact an IEEE Content Specialist today to learn more about getting access to these courses for your organization.
Interested in the course for yourself? Visit the IEEE Learning Network.
Resources
Chen, Xi, Ding, Yimin, Duan, Yao, Guo, Xuexue, Ni, Xingjie (17 July 2020). Molding free-space light with guided wave–driven metasurfaces. ScienceAdvances.
The Benefits of Finite Element Analysis in Manufacturing. Manor Tool.
Agrawal, Arti , Rahman, B. M. Azizur. (2013). Finite Element Modeling Methods for Photonics. Artech House.