Reflective Toraldo pupil for high-resolution millimeter-wave astronomy.

A novel, to the best of our knowledge, beam-shaping reflective surface for high-resolution millimeter/submillimeter-wave astronomy instruments is presented. The reflector design is based on Toraldo's super-resolution principle and implemented with annulated binary-phase coronae structure inspired by the achromatic magnetic mirror approach. A thin, less than half a free-space wavelength, reflective Toraldo pupil device operated in the W-band has been fabricated using mesh-filter technology developed at Cardiff University. The device has been characterized on a quasi-optical test bench and demonstrated expected reduction of the beam width upon reflection at oblique incidence, while featuring a sidelobe level lower than -10. The proposed reflective Toraldo pupil structure can be easily scaled for upper millimeter and infrared frequency bands as well as designed to transform a Gaussian beam into a flat-top beam with extremely low sidelobe level.