11 research outputs found

    Miniaturized Phase-Shifters for Ka-Band Phased Array Antennas

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    Realizing robust and stable two-way links between the mobile users and the satellite is an extremely challenging RF/Microwave engineering problem. Low cost and low profile phased array is considered as the best solution for this problem. High performance low cost and miniaturized variable phase shifter is a key enabling technology for such complex smart phased array antenna system. This thesis aims at the investigation of the existing solutions to realize miniaturized, low-cost and at the same time integrable phase shifters for commercial phased array antenna systems. Among few existing approaches, analog phase shifting devices based on voltage-tunable materials offers a promising solution. Liquid Crystal (LC) and Barium Strontium Titanate (BST) are the two voltage tunable materials, which, beside their own primary applications, have found their way into Microwave and mm-Wave tunable device technologies. In this study the utilization of LC and BST in analog phase shifters has been rigorously investigated, the advantages and drawbacks of each when applied in different realizations have been discussed and further development and improvements in designs have been suggested. To achieve more compact designs for Ka-band phase shifters, a comprehensive design methodology for tunable filter-type phase shifter is proposed in this dissertation. The most commonly used phase shifting architectures for the phased array antennas are RF, LO, IF and base-band phase shifting. It should be mentioned that LO, IF and base-band phase shifting are not suitable for phased arrays with large number of elements due to the formidable cost and complexity, particularly for Tx phased array systems which require one phase shifter per antenna element to meet the radiation mask. Therefore, this thesis is concentrated on RF (Microwave/mm-Wave) phase shifting, which is the most common for large phased array antenna systems. Since one of the most important requirement in the design of Ka-Band phase shifters for phased array systems is the high level of miniaturization, dictated by antenna element spacing constraint, the thesis also addresses the highly compact structure of such phase shifters. In particular, a novel phase shifting concept based on very high dielectric constant materials has been explored. It is shown that by using this new concept, a highly miniaturized variable phase shifter with more than 360 degrees phase tuning range is attainable.4 month

    Angle-multiplexed metasurfaces: encoding independent wavefronts in a single metasurface under different illumination angles

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    The angular response of thin diffractive optical elements is highly correlated. For example, the angles of incidence and diffraction of a grating are locked through the grating momentum determined by the grating period. Other diffractive devices, including conventional metasurfaces, have a similar angular behavior due to the fixed locations of the Fresnel zone boundaries and the weak angular sensitivity of the meta-atoms. To alter this fundamental property, we introduce angle-multiplexed metasurfaces, composed of reflective high-contrast dielectric U-shaped meta-atoms, whose response under illumination from different angles can be controlled independently. This enables flat optical devices that impose different and independent optical transformations when illuminated from different directions, a capability not previously available in diffractive optics

    Computational complex optical field imaging using a designed metasurface diffuser

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    Various speckle-based computational imaging techniques that exploit the ability of scattering media to transfer hidden information into the speckle pattern have recently been demonstrated. Current implementations suffer from several drawbacks associated with the use of conventional scattering media (CSM), such as their time-consuming characterization, instability with time, and limited memory-effect range. Here we show that by using a random dielectric metasurface diffuser (MD) with known scattering properties, many of these issues can be addressed. We experimentally demonstrate an imaging system with the ability to retrieve complex field values using a MD and the speckle-correlation scattering matrix method. We explore the mathematical properties of the MD transmission matrix such as its correlation and singular value spectrum to expand the understanding about both MDs and the speckle-correlation scattering matrix approach. In addition to a large noise tolerance, reliable reproducibility, and robustness against misalignments, using the MD allows us to substitute the laborious experimental characterization procedure of the CSM with a simple simulation process. Moreover, dielectric MDs with identical scattering properties can easily be mass-produced, thus enabling real-world applications. Representing a bridge between metasurface optics and speckle-based computational imaging, this work paves the way to extending the potentials of diverse speckle-based computational imaging methods for various applications such as biomedical imaging, holography, and optical encryption

    Single-shot quantitative phase gradient microscopy using a system of multifunctional metasurfaces

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    Quantitative phase imaging (QPI) of transparent samples plays an essential role in multiple biomedical applications, and miniaturizing these systems will enable their adoption into point-of-care and in vivo applications. Here, we propose a compact quantitative phase gradient microscope (QGPM) based on two dielectric metasurface layers, inspired by a classical differential interference contrast (DIC) microscope. Owing to the multifunctionality and compactness of the dielectric metasurfaces, the QPGM simultaneously captures three DIC images to generate a quantitative phase gradient image in a single shot. The volume of the metasurface optical system is on the order of 1 mm³. Imaging experiments with various phase resolution samples verify the capability to capture quantitative phase gradient data, with phase gradient sensitivity better than 92.3 mrad μm⁻¹ and single-cell resolution. The results showcase the potential of metasurfaces for developing miniaturized QPI systems for label-free cellular imaging and point-of-care devices

    Cascaded Multifunctional Metasurfaces for Single-shot Quantitative Phase Gradient Microscopy

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    We experimentally demonstrate a single-shot quantitative phase gradient microscope by two cascaded multifunctional metasurfaces. Experiments with various specimens show the capability to capture quantitative phase gradient images with single-cell resolution and low noise levels

    Computational complex optical field imaging using a designed metasurface diffuser

    Get PDF
    Various speckle-based computational imaging techniques that exploit the ability of scattering media to transfer hidden information into the speckle pattern have recently been demonstrated. Current implementations suffer from several drawbacks associated with the use of conventional scattering media (CSM), such as their time-consuming characterization, instability with time, and limited memory-effect range. Here we show that by using a random dielectric metasurface diffuser (MD) with known scattering properties, many of these issues can be addressed. We experimentally demonstrate an imaging system with the ability to retrieve complex field values using a MD and the speckle-correlation scattering matrix method. We explore the mathematical properties of the MD transmission matrix such as its correlation and singular value spectrum to expand the understanding about both MDs and the speckle-correlation scattering matrix approach. In addition to a large noise tolerance, reliable reproducibility, and robustness against misalignments, using the MD allows us to substitute the laborious experimental characterization procedure of the CSM with a simple simulation process. Moreover, dielectric MDs with identical scattering properties can easily be mass-produced, thus enabling real-world applications. Representing a bridge between metasurface optics and speckle-based computational imaging, this work paves the way to extending the potentials of diverse speckle-based computational imaging methods for various applications such as biomedical imaging, holography, and optical encryption

    Hyperspectral imager with folded metasurface optics

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    Hyperspectral imaging is a key characterization technique used in various areas of science and technology. Almost all implementations of hyperspectral imagers rely on bulky optics including spectral filters and moving or tunable elements. Here, we propose and demonstrate a line-scanning folded metasurface hyperspectral imager (HSI) that is fabricated in a single lithographic step on a 1 mm thick glass substrate. The HSI is composed of four metasurfaces, three reflective and one transmissive, that are designed to collectively disperse and focus light of different wavelengths and incident angles on a focal plane parallel to the glass substrate. With a total volume of 8.5 mm^3, the HSI has spectral and angular resolutions of ∼1.5 nm and 0.075°, over the 750–850 nm and −15° to +15° degree ranges, respectively. Being compact, light weight, and easy to fabricate and integrate with image sensors and electronics, the metasurface HSI opens up new opportunities for utilizing hyperspectral imaging where strict volume and weight constraints exist. In addition, the demonstrated HSI exemplifies the utilization of metasurfaces as high-performance diffractive optical elements for implementation of advanced optical systems

    Hyperspectral imager with folded metasurface optics

    Get PDF
    Hyperspectral imaging is a key characterization technique used in various areas of science and technology. Almost all implementations of hyperspectral imagers rely on bulky optics including spectral filters and moving or tunable elements. Here, we propose and demonstrate a line-scanning folded metasurface hyperspectral imager (HSI) that is fabricated in a single lithographic step on a 1 mm thick glass substrate. The HSI is composed of four metasurfaces, three reflective and one transmissive, that are designed to collectively disperse and focus light of different wavelengths and incident angles on a focal plane parallel to the glass substrate. With a total volume of 8.5 mm^3, the HSI has spectral and angular resolutions of ∼1.5 nm and 0.075°, over the 750–850 nm and −15° to +15° degree ranges, respectively. Being compact, light weight, and easy to fabricate and integrate with image sensors and electronics, the metasurface HSI opens up new opportunities for utilizing hyperspectral imaging where strict volume and weight constraints exist. In addition, the demonstrated HSI exemplifies the utilization of metasurfaces as high-performance diffractive optical elements for implementation of advanced optical systems

    Folded Dielectric Metasurface Platform for Compact Optical Systems

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    We present a compact folded metasurface optics platform that offers a low-cost and robust solution for the design and realization of compact optical systems. Specifically, we introduce the design and implementation of a miniature spectrometer and a hyperspectral imager as examples showcasing the platform potentials

    Angle-Multiplexed Metasurfaces: Encoding Independent Wavefronts in a Single Metasurface under Different Illumination Angles

    No full text
    The angular response of thin diffractive optical elements is highly correlated. For example, the angles of incidence and diffraction of a grating are locked through the grating momentum determined by the grating period. Other diffractive devices, including conventional metasurfaces, have a similar angular behavior due to the fixed locations of the Fresnel zone boundaries and the weak angular sensitivity of the meta-atoms. To alter this fundamental property, we introduce angle-multiplexed metasurfaces, composed of reflective high-contrast dielectric U-shaped meta-atoms, whose response under illumination from different angles can be controlled independently. This enables flat optical devices that impose different and independent optical transformations when illuminated from different directions, a capability not previously available in diffractive optics
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