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What Is a Metalens?
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Metalens or metalenses, the cutting-edge innovation in optical technology, are not your ordinary, curved lenses. Metalenses are flat lenses that use metasurfaces to focus light.
A metalens differs from a traditional curved lens by its shape and surface. Traditionally, combinations of curved lenses, such as those in cameras, manipulate light to go to a receiver such as a sensor or the eye. Multiple lenses are usually needed to correct various image aberrations. However, a stack of bulky lenses takes a lot of space, which is a consideration for compact systems such as cell phone cameras and augmented reality / virtual reality (AR/VR) systems.
Figure 1. Traditional curved lenses ray trace (left) and metalens ray trace (right)
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How Do Metalenses Work and What Problems Do They Solve?
Metalenses usually consist of millions of subwavelength unit-cells called meta-atoms, which modulate light locally and coherently over the entire metasurface. The shape and/or size of each meta-atom is determined locally based on overall performance of the metalens.
Subwavelength nano-atoms can delay the phase of light, and when properly arranged on the surface, metalenses can create the same desired phase profile as a classic curved lens. Mature lithography technology supports large-scale production of patterned layouts.
Metalenses will be a key technology enabling the next generation of compact imaging, sensing, and display applications. They can also perform intricate wavefront engineering in a single optic, which is highly appealing for a range of applications.
The physical attributes of metalenses — their thin, flat, and lightweight nature — make them incredibly advantageous, especially concerning space and weight. They can help minimize optical products by replacing bulkier curved lenses with thin, flat surfaces while improving optical stability and quality of focus over more conventional lenses — see reference [1].
They're easy to manufacture, cost-effective, and integrate easier with other technologies. For example, with superior light-manipulating abilities like polarization, metalenses enhance imagery, potentially enabling new capabilities for optical design.
Figure 2. Near-IR wide-field-of-view Huygens metalens for outdoor imaging applications showing (L-R) Object, Aperture, Metalens, and Image
Which Industries and Applications Can Benefit from Metalenses?
The development of metasurfaces has helped open opportunities to create optical components with new and exciting applications, from sensing in medicine to imaging and consumer electronics, such as smartphones and augmented reality/virtual reality (AR/VR) systems — see reference [1].
Optical design engineers, research and development (R&D) engineers, scientists, semiconductor foundries, research institutes, and similar organizations can use metalenses for innovative and compact designs.
How Do You Develop and Model a Metalens?
Designing a metalens with millions of variables is a uniquely challenging task. You must meet multiple specifications, including achromaticity, large field of view and polarization behavior with a few elements. As explained in the work of Prof. Federico Capasso’s group in reference [1], metalens design has traditionally been manual and requires extensive design experience and a deep understanding of fundamental physics.
To design a metalens, a user would need to specify the set of lenses and its parameters in the optical system, as well as the desired target patterns and focus lengths.
In the traditional manual design approach, a deep understanding of physics and significant design experience is needed. For a semi-automatic multi-domain approach, there is still tremendous manual work to lay out metalenses.
Now there is a fully automated tool with inverse design capability that designers at all levels of expertise can use to create novel metalens designs quickly and easily. The key design-enabling features of the MetaOptic Designer tool enable simultaneous optimization of multiple design goals, including different launch and target fields and performance metrics.
The tool supports mixed optical systems that combine metasurfaces with conventional lenses. The efficient optimization and simulation algorithms generate accurate results, validated by a rigorous finite-difference time-domain (FDTD) method, and the powerful and user-friendly features significantly reduce design-to-validation cycles.[1]
Figure 3. Achromatic metalens
Figure 4. Wide angle metalens
Figure 5. Chiral hologram with input (left), desired (middle), and output (right)
Figure 6. Ray-based design starting point (left); MetaOptic Designer analysis and further optimization (middle); RSoft FullWAVE FDTD to validate final design (right) [3]
What Solutions Does Keysight Offer for Designing Metalenses?
Keysight is fueling this wave of optical technology innovation with different design tools.
MetaOptic Designer is an unprecedented inverse design tool that takes user-specified criteria and generates metalenses/metasufaces for optimal design performance. Results are validated by a rigorous finite-difference time-domain (FDTD) method to ensure accurate results. In addition, MetaOptic Designer’s powerful, user-friendly interface significantly reduces design-to-validation cycles. MetaOptic Designer, and its characteristic AI, fast-track design process right from inception to fabrication, delivering top-tier designs and simulating their significance in real-world applications.
CODE V MetaOptic Module offers familiar workflows for optical design engineers. The CODE V design process is like that of the diffractive optical elements. It offers a great advantage for optical design engineers seeking to use metalens in their designs.
Generate Optimal Metalens Designs Quickly and Efficiently
Keysight is supporting this new world of innovation with MetaOptic Designer, which provides efficient optimization and simulation algorithms to help generate metalens designs quickly.
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