Multilevel diffractive lens in the MWIR with extended depth-of-focus and wide field-of-view.

Optics in the mid-wave-infra-red (MWIR) band are generally heavy, thick and expensive. Here, we demonstrate multi-level diffractive lenses; one designed using inverse design and another using the conventional propagation phase (the Fresnel zone plate or FZP) with diameter = 25 mm and focal length = 25 mm operating at λ=4µm. We fabricated the lenses by optical lithography and compared their performance. We show that the inverse-designed MDL achieves larger depth-of-focus and better off-axis performance when compared to the FZP at the expense of larger spot size and reduced focusing efficiency. Both lenses are flat with thickness ≤0.5 mm and weigh ≤3.63 g, which are far smaller than their conventional refractive counterparts.

Parker Solar Probe Imaging of the Night Side of Venus.

We present images of Venus from the Wide-Field Imager for Parker Solar Probe (WISPR) telescope on board the Parker Solar Probe (PSP) spacecraft, obtained during PSP's third and fourth flybys of Venus on 2020 July 11 and 2021 February 20, respectively. Thermal emission from the surface is observed on the night side, representing the shortest wavelength observations of this emission ever, the first detection of the Venusian surface by an optical telescope observing below 0.8 µm. Consistent with previous observations at 1 µm, the cooler highland areas are fainter than the surrounding lowlands. The irradiances measured by WISPR are consistent with model predictions assuming a surface temperature of T = 735 K. In addition to the thermal emission, the WISPR images also show bright nightglow emission at the limb, and we compare the WISPR intensities with previous spectroscopic measurements of the molecular oxygen nightglow lines from Venus Express.

Large aperture adaptive doublet polymer lens for imaging applications.

We report a full design process-finite element modeling, fabrication, and characterization-of adaptive doublet polymer lenses. A first-order model was developed and used to design fluidic doublets, analogous to their glass counterparts. Two constant-volume fluidic chambers were enclosed by three flexible membranes, resulting in a variable focal length doublet with a clear aperture of 19.0 mm. Chromatic focal shift was then used to compare numerical modeling to experimentally measured results over a positive focal length range of 55-200 mm (f/2.89 to f/10.5).