In this work, using the maskless lithography technique, we have fabricated a series of square Ag/SiN/Ag magnetic absorbers with different side lengths. Multiple absorption peaks occur and are analyzed with the help of their field distribution simulation. The absorption peaks coming from the first and third magnetic resonance modes can be arbitrarily modulated by changing the side lengths. The magnetic absorbers exhibit strong absorption, polarization selectivity and arbitrary adjustability. Absorption peaks dominated by the first magnetic resonance modes possess high polarization selectivity, whereas absorption peaks dominated by the phonons of SiN are polarization-insensitive. Such magnetic metamaterials would advance laser techniques and optical device applications.

No abstract

A double-layer broadband high-transmission terahertz linear-to-circular polarization metasurface is experimentally demonstrated in frequencies between 0.46 and 0.62 THz. The measured results show a good agreement with the simulations. The values of co-polarization transmission coefficients [Formula: see text] and [Formula: see text] remain above 0.82 in both simulation and experiment, and the simulated and measured axial ratio is 26.2% and 29.6%, respectively. Moreover, the experimental ellipticity remains above 0.98 in the region from 0.5 to 0.62 THz. The average measured polarization conversion ratio is 0.68. The multi-reflection and transmission interference model is used to explain the physical mechanism of polarization conversion. The proposed structure could be used in terahertz transmission and detection because of its stable, high ellipticity and transmittance.