High-NA achromatic metalenses by inverse design

Chung, Haejun; Miller, Owen D.

doi:10.1364/oe.385440

Cited by 218 publications

(156 citation statements)

References 74 publications

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“…(3) and expressing ∆T err in terms of S by inverting Eq. (13). This leads to a looser bandwidth bound if the Strehl ratio decreases, suggesting that a relaxation of the imaging performance of the metalens allows for a broader bandwidth, as expected.…”

Section: Resultssupporting

confidence: 52%

“…Instead, all the metalens designs obey our limits based on Tucker's or Miller's TBP (see Fig. 2(b) and Table 1), including recent ultrabroadband metalenses obtained using free-form all-area optimization and inverse design [13].…”

Section: Resultsmentioning

confidence: 99%

“…2(b) we include both the bound for ideal metalenses with no aberrations (lower solid blue curve), and a bound for highly aberrated metalenses with an error ∆T err = 0.9∆T (upper solid blue curve), corresponding to low values of Strehl ratio according to Eq. (13). Most published metalens designs are below the bound for ideal metalenses, with only a handful of designs exceeding this limit.…”

Section: Resultsmentioning

confidence: 99%

“…It is therefore not surprising that, even when considering free-form all-area optimization of dielectric metalenses as in [13], the optimization tends to create a spatial distribution of material with "channels" that resemble waveguide segments. It is also not surprising that many of the designs we considered are relatively close to the limit, as shown in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…In conventional optics, it is possible to stack various lenses to correct chromatic aberrations [6], but at the price of making the overall system more bulky and costly. It is therefore remarkable that, in recent years, different groups have demonstrated metalenses with a fixed focal length over a large range of wavelengths, some even surpassing the achromatic performance of conventional lens systems (at least for normal incidence) [7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

Section: Introductionmentioning

confidence: 99%

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Focusing on bandwidth: achromatic metalens limits

Presutti

Monticone

2020

Optica

144

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Metalenses have shown great promise in their ability to function as ultracompact optical systems for focusing and imaging. Remarkably, several designs have been recently demonstrated that operate over a large range of frequencies with minimized chromatic aberrations, potentially paving the way for ultrathin achromatic optics. Here, we derive fundamental bandwidth limits that apply to broadband optical metalenses, regardless of their implementation. Specifically, we discuss how the product between achievable time delay and bandwidth is limited in any timeinvariant system, and we apply well-established bounds on this product to a general focusing system. We then show that all metalenses designed thus far obey the appropriate bandwidth limit. The derived physical bounds provide a useful metric to compare and assess the performance of different devices, and offer fundamental insight into how to design better broadband metalenses.

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Section: Resultssupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Focusing on bandwidth: achromatic metalens limits

Presutti

Monticone

2020

Optica

144

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Fundamental Limits to the Refractive Index of Transparent Optical Materials

2021

Self Cite

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Increasing the refractive index available for optical and nanophotonic systems opens new vistas for design, for applications ranging from broadband metalenses to ultrathin photovoltaics to high‐quality‐factor resonators. In this work, fundamental limits to the refractive index of any material are derived, given only the underlying electron density and either the maximum allowable dispersion or the minimum bandwidth of interest. In the realm of small to modest dispersion, the bounds are closely approached and not surpassed by a wide range of natural materials, showing that nature has already nearly reached a Pareto frontier for refractive index and dispersion. Conversely, for narrow‐bandwidth applications, nature does not provide the highly dispersive, high‐index materials that the bounds suggest should be possible. The theory of composites to identify metal‐based metamaterials that can exhibit small losses and sizeable increases in refractive index over the current best materials is used. Moreover, if the “elusive lossless metal” can be synthesized, it is shown that it would enable arbitrarily high refractive index in the high‐dispersion regime, nearly achieving the bounds even at refractive indices of 100 and beyond at optical frequencies.

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Pushing the Limits of Functionality‐Multiplexing Capability in Metasurface Design Based on Statistical Machine Learning

Xiong

et al. 2022

Advanced Materials

133

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metasurface research has spawned new types of flat optical components including beam deflectors, [4] high-quality-factor diffractors, [5] wave plates, [6] lenses, [7,8] and holograms. [9,10] Compared with their bulky counterparts that often rely on the phase accumulation of light propagating through conventional media, metasurface-based components can efficiently manipulate light by a deep subwavelength interface, making them compact, easy for integration, and relatively low loss, especially when dielectric materials are used. [11] In addition, the large flexibility in metasurface design offers unique ability to control light for multipurposed tasks that are usually inaccessible based on natural materials, yielding prescribed optical responses to different combinations of light characteristics such as the frequency, phase, angle of incidence, and polarization. [12][13][14][15][16][17][18][19][20] The exotic optical properties of metasurfaces originate from the engineered light-structure interactions. The conventional design approach heavily relies on template-based parameter sweep via numerical simulations to find eligible meta-atom structures, which could be facilitated by physical principles such as plasmonic resonance, [21] Mie theory, [22] or Pancharatnam-Berry (PB) phase for circular polarized light. [23] In the case of multifunctional metasurfaces, the design routines often utilize an empirical decoupling of the meta-atom response using multimode resonance in dielectric pillars, [24] As 2D metamaterials, metasurfaces provide an unprecedented means to manipulate light with the ability to multiplex different functionalities in a single planar device. Currently, most pursuits of multifunctional metasurfaces resort to empirically accommodating more functionalities at the cost of increasing structural complexity, with little effort to investigate the intrinsic restrictions of given meta-atoms and thus the ultimate limits in the design. In this work, it is proposed to embed machine-learning models in both gradientbased and nongradient optimization loops for the automatic implementation of multifunctional metasurfaces. Fundamentally different from the traditional two-step approach that separates phase retrieval and meta-atom structural design, the proposed end-to-end framework facilitates full exploitation of the prescribed design space and pushes the multifunctional design capacity to its physical limit. With a single-layer structure that can be readily fabricated, metasurface focusing lenses and holograms are experimentally demonstrated in the near-infrared region. They show up to eight controllable responses subjected to different combinations of working frequencies and linear polarization states, which are unachievable by the conventional physics-guided approaches. These results manifest the superior capability of the data-driven scheme for photonic design, and will accelerate the development of complex devices and systems for optical display, communication, and computing.

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High-NA achromatic metalenses by inverse design

Cited by 218 publications

References 74 publications

Focusing on bandwidth: achromatic metalens limits

Focusing on bandwidth: achromatic metalens limits

Fundamental Limits to the Refractive Index of Transparent Optical Materials

Pushing the Limits of Functionality‐Multiplexing Capability in Metasurface Design Based on Statistical Machine Learning

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