Reparameterization Approach to Gradient-Based Inverse Design of Three-Dimensional Nanophotonic Devices

Gershnabel, Erez; Chen, Mingkun; Mao, Chenkai; Wang, Evan W.; Lalanne, Philippe; Fan, Jonathan A.

doi:10.1021/acsphotonics.2c01160

Cited by 7 publications

(6 citation statements)

References 43 publications

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“…Therefore, the improvement in the merit function would be smaller and potentially hinder the optimization process. To address this, we leverage a latent matrix that extends the domain to all real numbers (−∞, ∞) instead of restricting it to [0, 1], which is inspired by work on reparameterization to latent variables and the concept of latent noise vectors prevalent in generative adversarial networks (45)(46)(47). This latent matrix is mapped to the device density using the pattern generator function.…”

Section: Optimization Results and Working Principlesmentioning

confidence: 99%

Freeform metasurface color router for deep submicron pixel image sensors

Kim,

Hong,

Jang

et al. 2024

Sci. Adv.

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Advances in imaging technologies have led to a high demand for ultracompact, high-resolution image sensors. However, color filter–based image sensors, now miniaturized to deep submicron pixel sizes, face challenges such as low signal-to-noise ratio due to fewer photons per pixel and inherent efficiency limitations from color filter arrays. Here, we demonstrate a freeform metasurface color router that achieves ultracompact pixel sizes while overcoming the efficiency limitations of conventional architectures by splitting and focusing visible light instead of filtering. This development is enabled by a fully differentiable topology optimization framework to maximize the use of the design space while ensuring fabrication feasibility and robustness to fabrication errors. The metasurface can distribute an average of 85% of incident visible light according to the Bayer pattern with a pixel size of 0.6 μm. The device and design methodology enable the compact, high-sensitivity, and high-resolution image sensors for various modern technologies and pave the way for the advanced photonic device design.

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Section: Optimization Results and Working Principlesmentioning

confidence: 99%

Freeform metasurface color router for deep submicron pixel image sensors

Kim,

Hong,

Jang

et al. 2024

Sci. Adv.

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“…To ensure ease of fabrication in a manner that streamlines with gradient-based freeform optimization, we utilize a reparameterization scheme in which the dimensions and positions of nanoscale elements within a super-pixel are represented as latent variables that can be transformed to physical layouts using analytic expressions 31 . In this manner, minimum feature size and gap constraints are hard coded into the element representations.…”

Section: Design Principlementioning

confidence: 99%

Large‐Area, High‐Numerical‐Aperture, Freeform Metasurfaces

Zhou,

Mao,

Gershnabel

et al. 2024

Laser & Photonics Reviews

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Nanophotonic devices are optical platforms capable of unprecedented wavefront control. To push the limits of experimental device performance, scalable design methodologies that combine the simplicity and fabricability of conventional design paradigms with the extended capabilities of freeform optimization are required. A novel gradient‐based design framework for large‐area freeform metasurfaces is introduced in which nonlocal interactions between simply shaped nanostructures, placed on an irregular lattice, are tailored to produce high‐order hybridized modes that support customizable large‐angle scattering profiles. Utilizing this approach, multifunctional super‐dispersive metalenses are designed and experimentally demonstrated. The approach to high‐numerical‐aperture radial metalenses capable of diffraction limited focusing and the generation of donut‐shaped point spread functions is also extended. It is anticipated that these concepts will have utility in super‐resolution microscopy, particle trapping, additive manufacturing, and metrology applications that require ultra‐high numerical apertures.

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“…Finally, a finite number of building blocks with desired phase shifts are collected from the pre-built meta-library and arranged with periodicity to realize targeted wavefront shaping. The forward design approach is widely used due to its interpretable framework and ease of implementation [ 19 , 20 ]. However, as the design constraints and design degrees of freedom scale up, it becomes less useful and may result in limit device performance.…”

Section: Introductionmentioning

confidence: 99%

Quasi-Freeform Metasurfaces for Wide-Angle Beam Deflecting and Splitting

et al. 2023

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Metasurfaces attracted extensive interests due to their outstanding ability to manipulate the wavefront at a subwavelength scale. In this study, we demonstrated quasi-freeform metasurfaces in which the radius, location, and height of the nanocylinder building blocks were set as optimized structure parameters, providing more degrees of freedom compared with traditional gradient metasurfaces. Given a desired wavefront shaping objective, these structure parameters can be collectively optimized utilizing a hybrid optimized algorithm. To demonstrate the versatility and feasibility of our method, we firstly proposed metasurfaces with deflecting efficiencies ranging from 86.2% to 94.8%, where the deflecting angles can vary in the range of 29°–75.6°. With further study, we applied our concept to realize a variety of high-efficiency, wide-angle, equal-power beam splitters. The total splitting efficiencies of all the proposed beam splitters exceeded 89.4%, where a highest efficiency of 97.6%, a maximum splitting angle of 75.6°, and a splitting uniformity of 0.33% were obtained. Considering that various deflecting angles, and various splitting channels with different splitting angles, can be realized by setting the optical response of metasurfaces as the optimization target, we believe that our method will provide an alternative approach for metasurfaces to realize desired wavefront shaping.

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Reparameterization Approach to Gradient-Based Inverse Design of Three-Dimensional Nanophotonic Devices

Cited by 7 publications

References 43 publications

Freeform metasurface color router for deep submicron pixel image sensors

Freeform metasurface color router for deep submicron pixel image sensors

Large‐Area, High‐Numerical‐Aperture, Freeform Metasurfaces

Quasi-Freeform Metasurfaces for Wide-Angle Beam Deflecting and Splitting

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