Meta-optical computational imaging systems for large aperture, aberration-free imaging

Large aperture optics are important for various applications including remote sensing and gigapixel imaging, but such optics are generally very heavy. For example, the optics in the Hubble telescope (aperture of ~ 2m) are on the order of 1000 kg. The emerging field of meta-optics, which utilizes arrays of sub-wavelength nano-scatterers to manipulate wave-fronts can drastically reduce the size and weight of optical systems. Each scatterer is individually engineered and arranged in a precisely aligned grid to enable optical functionalities that are difficult, if not impossible to achieve using conventional refractive optics. Moreover, these flat optical elements can be ultrathin, with active layer thicknesses on the order of a single optical wavelength. However, the imaging performance and achievable apertures of the most sophisticated meta-optics are currently constrained by fundamental limitations of electromagnetic responses, Seidel aberrations, available electromagnetic design software, and practical manufacturing challenges.   Tunoptix proposes to address these limitations by using a photolithography compatible metasurface-based computational imaging system where the metasurface is supported by an image processing backend to produce high fidelity, aberration-free images. Tunoptix’s effort is comprised of three complementary thrusts focused on: (1) the design and optimization of centimeter and decimeter-scale meta-optics with accompanying reconstruction software, (2) the development of a scalable photolithography fabrication process for centimeter and decimeter-scale metasurfaces, and (3) the characterization of the fabricated metalenses and data acquisition for use in learned reconstruction models.   In thrust (1), Tunoptix will use metasurface scatterer geometries described by simple shapes such as square pillars with modest aspect ratios to make our designs easily compatible with conventional deep UV photolithography techniques. Instead of using difficult-to-fabricate intricate scatterer geometries to correct optical aberrations, Tunoptix will instead leverage computational imaging techniques to perform image reconstruction.  In thrust (2), Tunoptix will fabricate the centimeter-scale designs by using a foundry service. The metasurface designs will be amended such that they fall within the design rules of the chosen foundry service. In addition, to fabricate decimeter-scale designs, a step-and-stitch process will be developed to minimize the required reticles.   In thrust (3), the fabricated metalenses will be fully measured in terms of their chromatic and Seidel aberrations by measuring their point spread functions and characterized in terms of their dependence on incident wavelength, angle of incidence, and object depth. These point spread functions will then be used to reconstruct high quality images in lab and real-world settings. A learned reconstruction algorithm will then be fine-tuned using the point spread function and imaging data.