The transformative technology behind Nautilus are the ultralight, very large-aperture engineered material multi-order diffractive lenses (MOD-EnMat) 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 MOD-EnMat 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 MOD-EnMat 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 and advanced, high-order harmonics surface optimized for astrophysical observations.
The MOD-EnMat lenses designed by the Nautilus optical design and fabrication team can be replicated rapidly and at low cost. The Nautilus Array is made possible by the lightweight, replicated MOD-EnMat lenses that allow light-weight telescope structure, overall greatly reduced launch costs, combined with cost-effective fabrication of large quantities of the lenses.
Prototypes at University of Arizona
The Nautilus team has been developing diffractive-transmissive optics and studying the design, fabrication, and testing of large-scale MOD-EML since 2015. Our team has designed and fabricated multiple generations of MOD-EML lenses. We have also successfully replicated lenses. As of November 2017 laboratory and on-sky tests using a Celestron refracting telescope in which the original refractive lens has been replaced with a small-scale MOD-EML element.