The transformative technology behind the Nautilus Observatory concept are the ultralight, very large-aperture engineered material multi-order engineered material diffractive (MODE) lenses developed at The University of Arizona’s College of Optical Sciences.
Traditional lenses use refraction – the change of light’s direction as it enters a medium with different refractive index – to focus light onto the focal plane, thereby creating images. However, large lenses are exceedingly difficult to manufacture.
The MODE lenses (multi-order diffractive engineered material lenses) are very light-weight diffractive-transmissive alternatives to the heavy reflective elements (mirrors) used in state-of-the-art ground- and space-based telescopes. Technology similar to MODE lenses is used in some commercial optics, including high-quality Canon EF photo-lenses. The optimized multi-order design of these lenses provides essentially achromatic, diffraction-limited performance.
Other Large Diffractive Lens-based Telescope Concepts
Large space telescopes utilizing conceptually similar, but distinct technologies have been in development by multiple groups: a team led by Rod Hyde at Lawrence Livermore National Laboratory, developed the Eyeglass concept, a 20m diameter space telescope also utilizing transmissive diffractive optics. In 2002 a 5m prototype was built at LLNL with funding from DARPA. The Eyeglass concept is using a very large number of flat glass panels that deployed in an origami fashion.
From 2010 DARPA has been pursuing MOIRE (Membrane Optic Imager Real-Time Exploitation), which also uses transmissive diffractive optics, but replaces the thin glass tiles with flexible optical membranes, in which the diffraction pattern is produced in a lithographic process. The MOIRE project demonstrated in 2013 a partial 5m diameter ground-based telescope, a milestone toward the eventual goal of a 20m diameter earth-observing space telescope. (DARPA MOIRE concept video , S&TR article on Eyeglass and MOIRE)
Our Nautilus project also uses diffractive transmissive optics, but with an advanced, high-order harmonics surface optimized for astrophysical observations.
The MODE lenses designed by the Nautilus team can be replicated rapidly and at low cost. The Nautilus Array is made possible by the lightweight, replicated MODE lenses that allow light-weight telescope structure, overall greatly reduced launch costs, combined with cost-effective fabrication of large quantities of the lenses.
Technology Development at University of Arizona
The Nautilus team has been developing diffractive-transmissive optics and studying the design, fabrication, and testing of large-scale MODE lenses since 2016. Our team has designed and fabricated multiple generations of MODE lenses. We have also successfully replicated lenses. In November 2017 we carried out successful laboratory and on-sky tests using a Celestron refracting telescope in which the original refractive lens has been replaced with a small-scale MODE element. In September 2018 we demonstrated a telescope with an achromatic MODE lens. In early 2019 we designed a new, high-performance color corrector for MODE telescopes. In 2022, we molded the first larger-diameter glass MODE lens segments, and completed the assembly of our KEYS mechanism for closed-loop lens segment alignment. We also completed a lens group for an advanced color corrector (also based on a hybrid diffractive-refractive lens).
Our team is currently working on increasing the size of the MODE lenses that can be fabricated and replicated, on developing a ground-based MODE telescope with increasingly large diameter lenses, and on mission concepts for pathfinder space telescopes.
