A new generation of quasi-optical (QO) systems with multiple refractive and reflective components are required for several (sub)-millimeter applications such as the next generation of communication systems, sensing and security imagers, and instrumentation for far-infrared astronomy. Currently, there are no numerically efficient and accurate modeling tools available to design such systems tailored to their moderate sizes, in terms of wavelength, and wide operational bandwidths. In this article, a numerically efficient and accurate technique is proposed for designing QO systems containing a cascade of homogeneous dielectric lens components. The methodology is based on sequential geometrical optics (GO) combined with an analysis in reception mode. Thanks to the computational efficiency of the proposed technique, we were able to embed it as the kernel for multiobjective optimizers to design complex multilens QO systems. Here, two indicative examples of such geometries targeting specific requirements and scenarios are showcased. The overall optimization technique is validated against in-house and commercial physical optics (PO) codes, as well as full-wave simulations where possible, with excellent agreement in both efficiency terms and far-field beam patterns. Moreover, the proposed technique achieves orders of magnitude faster execution times with respect to the currently available commercial tools. ... Read more

Lens based Microwave Kinetic Inductance Detectors combined with distributed absorbers are one of the main candidates for large format, extremely sensitive detector systems for Far Infrared Astronomy. In this paper, the optimal design of integrated dielectric lenses, based on the response of the distributed absorber to incident plane waves, is studied. For the analysis, two efficiency terms are defined, namely spectral and spillover efficiencies, decomposing the effect of the absorber’s response to incident plane waves from that of its physical dimensions, on the total power captured by the detector system. Linearly polarized absorbers, made of Aluminium strips are considered as an indicative absorber geometry, with or without a quarter-wavelength backing reflector. ... Read more