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1. Inverse design of acoustic metasurfaces using space-filling points

   https://doi.org/10.1063/5.0096869  

   Krishna, Arvind; Craig, Steven R.; Shi, Chengzhi; Joseph, V. Roshan (August 2022, Applied Physics Letters)

   Acoustic metasurfaces are two-dimensional materials that impart non-trivial amplitude and phase shifts on incident acoustic waves at a predetermined frequency. While acoustic metasurfaces enable extraordinary wavefront engineering capabilities, they are not developed well enough to independently control the amplitude and phase of reflected and transmitted acoustic waves simultaneously, which are governed by their geometry. We aim to solve the inverse design problem of finding a geometry to achieve a specified set of acoustic properties. The geometry is modeled by discretizing the continuous space into a finite number of elements, where each element can either be filled with air or solid material. Full wave simulations are performed to obtain the acoustic properties for a given geometry. It is computationally infeasible to simulate all geometries. To address this challenge, we develop an experimental design-based algorithm to efficiently perform the simulations. The algorithm starts with a few geometries and adaptively adds geometries to the set, such that they fill the entire space of the desired acoustic properties using a small fraction of the possible geometries. We find that the geometry needs to have at least 7 × 7 elements to obtain any given acoustic property with a tolerance of 5.4% of its maximum range. This is achieved by simulating 24 000 geometries using the proposed algorithm, which is only [Formula: see text] of the 563 × 10 12 possible geometries. The method provides a general solution to the inverse design problem that can be extended to control more acoustic properties. 

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2. Tunable, reconfigurable, and programmable acoustic metasurfaces: A review

   https://doi.org/10.3389/fmats.2023.1132585  

   Zabihi, Ali; Ellouzi, Chadi; Shen, Chen (March 2023, Frontiers in Materials)

   The advent of acoustic metasurfaces (AMs), which are the two-dimensional equivalents of metamaterials, has opened up new possibilities in wave manipulation using acoustically thin structures. Through the interaction between the acoustic waves and the subwavelength scattering, AMs exhibit versatile capabilities to control acoustic wave propagation such as by steering, focusing, and absorption. In recent years, this vibrant field has expanded to include tunable, reconfigurable, and programmable control to further expand the capacity of AMs. This paper reviews recent developments in AMs and summarizes the fundamental approaches for achieving tunable control, namely, by mechanical tuning, active control, and the use of field-responsive materials. An overview of basic concepts in each category is first presented, followed by a discussion of their applications and details about their performance. The review concludes with the outlook for future directions in this exciting field. 

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3. Split-Lohmann lenses for imaging and display

   https://doi.org/10.1117/12.3091235  

   Qin, Yingsi; Sankaranarayanan, Aswin C; O'Toole, Matthew (March 2026, SPIE)

   Gao, Liang; Zheng, Guoan; Lee, Seung Ah (Ed.)

   From the cameras in our phones to the lenses in head-mounted displays, optics shape both how we capture the world and how we experience virtual reality. Most conventional lenses are designed to bring a single plane into focus. In this article, we discuss a new class of computational lens—referred to as a Split-Lohmann lens—that provides spatially varying control over focal length. This capability is achieved by combining a phase-only spatial light modulator with the cubic phase plates used in Lohmann/Alvarez focus-tunable lenses. The resulting computational lens enables new imaging and display capabilities, including the ability to (i) make a flat display appear to have three-dimensional shape, and (ii) capture all-in-focus images of highly non-planar scenes. 

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4. Dynamic and Reconfigurable Acoustic Fields Enabled by Morphing Fluidic Holographic Lenses

   https://doi.org/10.1002/admt.202500741  

   Sayed_Ahmed, Moustafa; Shahab, Shima (November 2025, Advanced Materials Technologies)

   Abstract Morphing acoustic metasurfaces offer exciting possibilities for dynamically controlling wavefronts in space and time. This work presents a unified framework for reconfigurable acoustic holography using fluidic holographic lenses, capable of dynamically shaping ultrasound fields through volume‐controlled deformation. Two distinct but conceptually integrated implementations are introduced and experimentally validated: i) embedded fluidic lenses, which use 3D‐printed holograms immersed in a fluid medium to enable volumetric phase modulation, and ii) aperture‐defined fluidic lenses, which rely solely on membrane deformation over a geometrically shaped container opening to approximate target pressure fields without pre‐fabricated holograms. Both approaches exploit fluid‐structure interactions to achieve continuous modulation of the acoustic field at the target plane. This programmable and hardware‐efficient strategy enables adaptive wavefront control without reliance on complex phased arrays or static rigid structures. The proposed system demonstrates reconfigurable acoustic patterning and establishes a generalizable foundation for dynamic acoustic wave engineering in applications such as biomedical imaging, particle manipulation, ultrasound haptics, and acoustic power transfer. 

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5. Electrically tunable chiral liquid crystal lens arrays

   https://doi.org/10.1117/12.2676160  

   Perera, Kelum; Haputhantrige, Nilanthi; Himel, Md_Sakhawat Hossain; Mostafa, Md; Adaka, Alex; Lavrentovich, Oleg D; Jákli, Antal I (September 2023, Proc. SPIE 12658, Liquid Crystals XXVII)

   Khoo, Iam Choon (Ed.)

   Lenses with tunable focal lengths play important roles in nature as well as modern technologies. In recent years, the demand for electrically tunable lenses and lens arrays has grown, driven by the increasing interest in augmented and virtual reality, as well as sensing applications. In this paper, we present a novel type of electrically tunable microlens utilizing polymer-stabilized chiral ferroelectric nematic liquid crystal. The lens offers a fast response time (5ms) and the focal length can be tuned by applying an in-plane electric field. The electrically induced change in the lens shape, facilitated by the remarkable sensitivity of the chiral ferroelectric nematic to electric fields, enables the tunable focal length capability. The achieved performance of this lens represents a significant advancement compared to electrowetting-based liquid lenses and opens exciting prospects in various fields, including biomimetic optics, security printing, solar energy concentration, and AR/VR devices. 

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