Design of Flat All-Dielectric Metasurface Lens for Antenna-Coupled Transition-Edge Sensor Bolometers.

The focal plane of a telescope for cosmic microwave background (CMB) observation typically contains a large-scale array of transition-edge sensor (TES) bolometers. Polarized planar antennas are easy to fabricate and integrate, compared to commonly used horn antennas in receiving modules. In order to enhance the directivity and coupling efficiency, a planar antenna is generally equipped with a hyper-hemispherical silicon lens. However, a Si lens has a large volume, and the fabrication and assembly processes are complex. A flat all-dielectric metasurface lens is proposed to replace Si-lens to converge beam and increase gain of a slot antenna. The all-dielectric structure of silicon holes with sub-wavelength thickness can change the volumetric fill factor to adjust the local effective refractive index, and thus manipulate the shape of wavefront while ensuring high transmission efficiency. The meta-lens was found to exhibit high gain, low cross polarization and good beam symmetry, as verified by simulated electric field amplitude distribution and far-field patterns at 225 GHz using CST microwave studio suite. The detector array and the meta-lens array can both be fabricated using standard planar photolithography technology, and the combination has the potential to achieve larger scale arrays. [ABSTRACT FROM AUTHOR]