Abstract

To unveil presently inscrutable details of the origins of our universe imprinted in the cosmic microwave background, future experiments in the millimeter and submillimeter range are focusing on the detection of fine features, which necessitate large and sensitive detector arrays to enable multichroic mapping of the sky. Currently, various approaches for coupling light to such detectors are under investigation, namely, coherently summed hierarchical arrays, platelet horns, and antenna-coupled planar lenslets. The last option offers increased bandwidth and a simpler fabrication while maintaining the desired optical performance. In this work, the design, fabrication, and experimental characterization of a prototype planar metamaterial phase-engineered lenslet operating in W-band [75 GHz; 110 GHz] is presented. Its radiated field, initially modeled and measured on a systematics-limited optical bench, is compared against a simulated hyperhemispherical lenslet, a more established technology. It is reported here that our device reaches the cosmic microwave background (CMB) specification for the next stages of experiments, demonstrating power coupling above 95% and beam Gaussicity above 97% while maintaining ellipticity below 10% and a cross-polarization level below ${-}21\;{\rm dB}$ through its operating bandwidth. Such results underline the potential advantages our lenslet can offer as focal optics for future CMB experiments.

© 2023 Optica Publishing Group

Thin flexible multi-octave metamaterial absorber for millimeter wavelengths

Giampaolo Pisano, Christopher Dunscombe, Peter Hargrave, Alexey Shitvov, and Carole Tucker
Appl. Opt. 62(9) 2317-2328 (2023)

Simulation of the optical system in the GroundBIRD telescope

Yonggil Jo, Jihoon Choi, Makoto Hattori, Shunsuke Honda, Tomonaga Tanaka, Miku Tsuji, Eunil Won, and Kyungmin Lee
Appl. Opt. 62(20) 5369-5378 (2023)

Sidelobe modeling and mitigation for a three mirror anastigmat cosmic microwave background telescope

Ian Gullett, Bradford Benson, Robert Besuner, Richard Bihary, John Carlstrom, Nick Emerson, Patricio A. Gallardo, Jillian Gomez, Cesiley L. King, Jeff McMahon, Jared L. May, Johanna M. Nagy, Tyler Natoli, Michael D. Niemack, Kate Okun, Stephen Padin, John E. Ruhl, Edward J. Wollack, and Jeff Zivick
Appl. Opt. 62(16) 4334-4341 (2023)

Achromatic half-wave plate for submillimeter instruments in cosmic microwave background astronomy: experimental characterization

Giampaolo Pisano, Giorgio Savini, Peter A. R. Ade, Vic Haynes, and Walter K. Gear
Appl. Opt. 45(27) 6982-6989 (2006)

Designs for a large-aperture telescope to map the CMB 10× faster

Michael D. Niemack
Appl. Opt. 55(7) 1688-1696 (2016)