Pedro Pinho | Searcharxiv

arXiv2026

Continuously Tunable Mid-Infrared Metalens Integrating Moiré and Pancharatnam-Berry Phases

A varifocal mid-infrared metalens designed for focusing applications is proposed to integrate both Pancharatnam-Berry (PB) and Moiré pattern-based mechanisms for rotational wavefront control. The metalens employs two identical nanostructured discs featuring germanium (Ge) meta-atoms on calcium fluoride (CaF2) substrates, operating as birefringent half-wave retarders with 99.95% Polarization Conversion Ratio (PCR) and 83.65% total transmission power at 2 μm wavelength. Full-wave numerical simulations demonstrate continuous focal length tunability from 45 μm to 12 μm by rotating the second disk from 30 deg. to 120 deg., corresponding to the numerical aperture values ranging from 22.99% to 68.67%. The proposed metalens maintains reconfigurable focusing regardless of the incident light polarization, while concurrently enabling polarization-controlled operation via a phase-modulation mechanism that yields inverse responses under Right Circular Polarization (RCP) and Left Circular Polarization (LCP) illuminations.

physics.optics↗

arXiv2026

Mechanically reconfigurable layered GRIN lenses for mid-infrared

This paper presents a concept of mechanically adjustable planar Gradientindex (GRIN) lens that can be used to realize reconfigurable focusing at mid-infrared (mid-IR) or millimeter-wave (mm-wave) frequencies. The concept is based on a multilayer design rooted in effective medium theory, where spatial refractive index profiles are synthesized using first-kind Chebyshev polynomials. Symmetric lateral displacement of the layers enables continuous modulation of the effective refractive index distribution, allowing controlled transitions between divergent, afocal, and convergent wavefronts. Numerical simulations demonstrate accurate focal tuning at mid-IR and mm-waves. In the mid-IR regime, focal lengths of about 56 μm and 24 μm are achieved with relative errors of around 4.4% and 10%, respectively. In the mm-wave regime, the lens produces focal lengths of about 158 mm and 128 mm with improved accuracies of 2.3% and 6.0%, respectively. The reconstructed refractive index profiles exhibit high similarity to ideal convex lens distributions, confirming the validity of the proposed synthesis approach. The proposed GRIN lens concept offers a scalable and physically interpretable approach to reconfigurable focusing, with potential applications in multimodal imaging, adaptive sensing, and telecommunication systems.

physics.optics↗