Development of Flat Silicon-Based Mesh Lens Arrays for Millimeter and Sub-millimeter Wave Astronomy

Abstract

The high sensitivity requirements set by future cosmic microwave background instruments are pushing the current technologies to produce highly performant focal plane arrays with thousands of detectors. The coupling of the detectors to the telescope optics is a challenging task. Current implemented solutions include phasedarray antenna-coupled detectors, platelet horn arrays, and lenslet-coupled planar antennas. There are also recent developments of flat graded-index lenses based on etched silicon. However, there are strong requirements in terms of electromagnetic performance, such as coupling efficiency and bandwidth, as well as requirements in terms of easy manufacturing and scalability, and it is very challenging to meet all these requirements with one of the above solutions. Here, we present a novel approach for producing flat metal-mesh lenslet arrays based on devices previously realized using the mesh-filter technology. We have now adapted the polypropylenebased mesh lens design to silicon substrates, thus providing a good mechanical match to the silicon-based detector arrays. The measured performance of prototype pixels operating at millimeter wavelengths is presented.

Overview of the medium and high frequency telescopes of the LiteBIRD space mission

“…The second type is based on variable phasedelays changing across the planar surface of the device. 24 Both demonstration lenses mimic the behavior of 300-mm diameter f/3.5 and f/4 classical lenses and reproduce fairly accurate Airy patterns. The performance of these lenses has been characterized in terms of frequency dependence, focal point variability, and deviations from the Airy pattern due to diffraction effects.…”

Super-capacitive patches and their use in low-pass filters and artificial dielectrics

“…The manufacture and verification of devices using super capacitive patches remains as further work due to the Covid-19 pandemic bringing work to a halt for the foreseeable future. The group at Cardiff has extensive experience with the modeling and construction of metal mesh millimeter-wave devices such as filters, half-wave plates, 3,28 Toraldo pupils, 29 magnetic mirrors, 30 and lenses, 14,31 so there is confidence that real-world implementations will match well.…”

“…[4][5][6][7][8][9] Capacitive meshes have been used to implement transmission low-pass filters, 10 anti-reflection coatings, 11 and GRIN lenses. [12][13][14] The properties of these devices are limited by the range of complex admittances available from the regular arrays of isolated square patches used in the meshes. There have been a number of designs of alternate patch shapes intended for various purposes, [15][16][17] sometimes discovered using nature-inspired algorithms [18][19][20][21][22][23] with mixed results.…”

Mesh low-pass filters for millimeter-wave applications: is the square capacitive shape optimal?

“…This has been demonstrated through a variety of conceptually different devices, half wave plates, 26,27 Toraldo pupils, 28 Magnetic mirrors, 29 Mesh lenses. 30,31…”