Brandon Farmer

Large-aperture fast multilevel Fresnel zone lenses in glass and ultrathin polymer films for visible and near-infrared imaging applications.

The ability to fabricate 4-level diffractive structures with 1 µm critical dimensions has been demonstrated for the creation of fast (∼f/3.1 at 633 nm) Fresnel zone lenses (FZLs) with >60% diffraction efficiency into the -1 focusing order and nearly complete suppression of 0 and +1 orders. This is done using tooling capable of producing optics with 800 mm apertures. A 4-level grating fabricated in glass at 300 mm aperture is shown to have <15  nm rms holographic phase error. Glass FZLs have also been used as mandrels for casting zero-thermal-expansion, 20 µm thick polymer films created with the 4-level structure as a route to mass replication of efficient diffractive membranes for ultralight segmented space-based telescope applications.

MOIRE: Membrane Material Property Characterizations, Testing and Lessons Learned

The Membrane Optical Imager (for) Real-time Exploitation (MOIRE) programs’ primary optics are constructed using a membrane material. Using a membrane enables the goal of the MOIRE program to launch large, greater than 10m aperture, optics while simultaneously reducing the weight of the optic. Achieving the desired performance of the membrane as an optical material is highly dependent upon the ability to control that membrane through the design and fabrication process via an understanding of the material properties of the membrane. This paper will cover the material property characterization, testing performed and lessons learned about the unique attributes of membranes, both as a material and as an optic.