Laser-based 3-D nanoprinting exemplified by two photon polymerization (TPP) has emerged as a practical route for additive manufacturing of sub-wavelength scale structures with broad applications in photonic packaging, nanofluidics, nanoelectromechanical systems, drug delivery, tissue engineering, and beyond. Conventional TPP relies on compound refractive lenses for light focusing. Here we present a novel alternative approach leveraging optical metalenses as the light manipulation element for versatile TPP fabrication. Using an inverse design algorithm, we show that the point spread function (PSF) of the metalens can be custom tailored to realize a variety of TPP writing modes, enabling fabrication of unconventional geometries difficult to process with traditional TPP. We demonstrated integration of metalenses with both commercial and home-built TPP systems, and experimentally implemented TPP to writing of 3-D polymer microstructures.
With their recognized advantages such as system-level size, weight and power (SWaP) benefits, minimal monochromatic aberration, polarization discrimination capacity, and low-cost at scale, metasurfaces have emerged as a transformative optics technology. Optical distortion, an important metric in many optical design specifications, has however rarely been discussed in the context of metalens optics. Here we present we present a generic approach for on-demand distortion correction using wide field-of-view (FOV) compound metalenses.
Metasurfaces, comprising arrays of ultrathin and planar nanostructures (termed "meta-atoms"), hold immense potential for high-performance optical devices, enabling the precise control of electromagnetic waves with subwavelength spatial accuracy. However, the design of meta-atom structures that satisfy multiple functional criteria and workability presents a formidable challenge that significantly increases the design complexity. To address this challenge, we developed an expedited process for constructing a versatile, fabrication-friendly meta-atom library. This process utilizes deep neural networks in conjunction with a meta-atom selector, which considers the practical fabrication limitations. To corroborate the effectiveness of our method, we successfully employed it to empirically validate a dual-band metasurface collimator utilizing intricate free-form meta-atoms.
Optical metasurfaces consist of planar subwavelength nanoantenna arrays that offer singular ability to sculpt
wavefront in almost arbitrary manners. They are thereby poised to become a powerful tool enabling compact and
high-performance optics. Multifunctional metasurfaces, whose optical responses vary according to the operation
conditions, further allow a plurality of new functionalities unattainable with traditional optical systems. In
this talk, we discuss the development of multifunctional meta-optics and demonstrations in imaging and sensing
applications.
Optical metasurfaces are planar subwavelength nanoantenna arrays engineered to provide on-demand manipulation of light, thereby enabling ultra-compact flat optics with high performance, small form-factor and new functionalities. When integrated with active elements, the pixelated, thin device architecture further facilitates dynamic tuning of local and global optical responses. Leveraging advanced materials, designs and architectures, we develop novel active and passive meta-optics capable of transforming a variety of optical systems that are traditionally bulky and complicated.
KEYWORDS: Zinc selenide, Thermography, Long wavelength infrared, Design and modelling, Silicon, Metalenses, Transmittance, Semiconducting wafers, Modulation transfer functions, Deep reactive ion etching
Wide field-of-view optics are crucial optical elements with extensive applications in imaging, display, and sensing. Conventional wide FOV optics rely on cascading multiple refractive optical elements to assemble ‘fisheye lenses’ that correct third-order Seidel aberrations. Here we experimentally demonstrate a flat lens design that achieves 140◦ FOV in the long-wave infrared band. The metalens was fabricated on a monolithic float zone Si wafer leveraging photolithography and deep reactive ion etching. Large metalenses with diameter exceeding 4 cm have been realized using this approach. Thermal imaging at ambient temperature was validated by coupling the metalens with a LWIR focal plane array.
Wide field-of-view (FOV) optics are essential components in many optical systems, with applications spanning imaging, display, sensing, and beam steering. Conventional refractive wide FOV optics often involve multiple stacked lenses, resulting in large size and weight as well as high cost. Metasurface lenses or metalenses promise a viable solution to realizing wide FOV optics without complex lens assembly. We review the various architectures of wide FOV metalenses, elucidate their fundamental operating principles and design trade-offs, and quantitatively evaluate and contrast their imaging performances. Emerging applications enabled by wide FOV metasurface optics are also discussed.
3-D sensing is a rapidly evolving technology impacting broad applications in computer vision. Existing 3-D cameras are restricted in field of view, resolution, and feature a complex multiple lens assembly. Here, we demonstrate a single piece fish-eye metalens in the visible band capable to perform diffraction-limited focusing and imaging over nearly 180-degree field of view. Our metalens has been shown to produce panoramic high-resolution imaging of a semi-circular target. Furthermore, we constructed a stereoscopic camera and performed panoramic depth measurements. We believe that the fisheye-metalens 3-D sensors is a promising platform empowering a range of emerging high-tech sectors.
With their recognized advantages such as system-level size, weight and power (SWaP) benefits, minimal monochromatic aberration, polarization discrimination capacity, and low-cost at scale, metasurfaces have emerged as a transformative optics technology. Here we present the applications of polarization-multiplexed, multifunctional metasurface optics for imaging and sensing. Specifically, depth resolved imaging using metalenses with custom-engineered point spread functions will be discussed.
Zoom lenses with adjustable focal lengths and magnification ratios are an crucial part for many optical imaging systems. Conventional zoom lenses comprise multiple refractive optics. Optical zoom is achieved with translational motion of multiple lens elements, which inevitably increases module size, cost, and complexity. Here, we present a zoom lens design based on multi-functional optical metasurfaces. It achieves large zoom ratios with diffraction-limited quality and minimal distortion. Also, it requires no mechanical moving parts. We demonstrate the concept with two embodiments, one in the visible with polarization-multiplexing, and the other in the mid-infrared with phase change materials. Both of them achieve 10x parfocal zoom consistent with the design.
Phase change materials or PCMs are truly remarkable compounds whose unique switchable properties have fueled an explosion of emerging applications in electronics and photonics. Nonetheless, if we discount their use in optical discs, PCMs’ immense application potential in photonics beyond data recording has only begun to unfold in the past decade. While the material requirements for optical or electronic data storage have been succinctly summarized as five key elements “writability, archival storage, erasability, readability, and cyclability” decades ago, these requirements are not universally relevant to the diverse set of photonic applications now being explored. It also comes as no surprise that existing PCMs, which have been heavily vetted for data storage, are not necessarily the optimal compositions for different use cases in optics and photonics. PCMs with their attributes custom-tailored for specific applications are therefore in demand as phase-change photonics continue to expand. Here we discuss the PCM selection and design strategies specifically for photonic applications as well as our recent work developing active integrated photonic devices and meta-surface optics based on new PCMs tailored for photonics.
Wide field-of-view (FOV) functionality is crucial for implementation of advanced optical devices with applications spanning medical imaging, 3-D sensing, projection display, and security surveillance. While conventional wide FOV operation relies upon complicated assembly of multiple lens elements, metasurface optics offer a compelling alternative to realize compact, light-weight, and high-performance wide FOV optical modules. Here we elucidate the physical principles and design guidelines which underlies our recent demonstration of a fisheye metalens with > 170˚ diffraction-limited FOV. An analytical model is discussed, and wide-FOV achromatic metalens designs developed with a combination of direct search optimization and deep learning algorithms is presented.
Optical metasurfaces, planar sub-wavelength nano-antenna arrays with the singular ability to sculpt wave front in almost arbitrary manners, are poised to become a powerful tool enabling compact and high-performance optics with novel functionalities. A particularly intriguing research direction within this field is active metasurfaces, whose optical response can be dynamically tuned post-fabrication, thus allowing a plurality of applications unattainable with traditional bulk optics. The efforts to date, however, still face major performance limitations in tuning range, optical quality, and efficiency especially for non-mechanical actuation mechanisms. In this paper, we introduce an active metasurface platform combining phase tuning covering the full 2π range and diffraction-limited performance using an all-dielectric, low-loss architecture based on optical phase change materials (O-PCMs). We present a generic design principle enabling binary switching of metasurfaces between arbitrary phase profiles. We implement the approach to realize a high-performance varifocal metalens. The metalens is constructed using Ge2Sb2Se4Te1 (GSST), an O-PCM with a large refractive index contrast and unique broadband low-loss characteristics in both amorphous and crystalline states. The reconfigurable metalens features focusing efficiencies above 20% at both states for linearly polarized light and a record large switching contrast ratio (CR) close to 30 dB. We further validate aberration-free and multi-depth imaging using the metalens, which represents the first experimental demonstration of a non-mechanical active metalens with diffraction-limited performance.
Optical metasurfaces consist of nanostructured meta-atom arrays that allow on-demand manipulation of the phase, amplitude and polarization of light. The promise of metasurface optics lies in the arbitrary wavefront control with an optically-thin, flat/conformal form factor and subwavelength-arrayed device architecture, in drastic contrast to traditional bulk optics. In this talk, we’ll discuss opportunities and challenges of using metasurfaces in imaging systems. We further present novel imaging optics and architectures enabled by ultra-thin, all-dielectric metasurfaces, such as ultra-wide field-of-view and reconfigurable meta-optics with unprecedented optical performance. We show that the judicially-engineered meta-optics can significantly boost the imaging performance, allow new functionalities and effectively reduce the size, weight, power and cost (SWaP-C) of future optical systems.
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