A polarizer is an optical filter that allows light waves of a specific polarization pass through while blocking light waves of other polarizations – similar to sunglasses that filter light in the visible range. These components can be integrated into THz equipment, such as sources and image acquisition setups, and applied in many different techniques including spectroscopy, microscopy, and astronomy to study and investigate materials.
Most commercial THz polarizers are free-standing wire grids of suspended micrometre-sized diameter wires. Large diameters, above 5 m, is a consequence of using suspended wires. Alternatively, smaller micro-wires could be fabricated on top of a support substrate such as silicon, however, this material only transmits 45% of the light.
INL – International Iberian Nanotechnology Laboratory researchers developed a new nanofabrication method for high-efficiency polarizers using small-sized wires (1 µm), a double-wire grid configuration, and transparent substrates. Alexandre Chícharo, Research Engineer at INL, explains that “new materials such as cyclic olefin copolymer (COC) have much higher transmittance (as high as 90%), resulting in ultra-transparent polarizers. In addition, the double-wire grid configuration presents a much higher performance in obtaining polarized THz when compared to a single plane of wires”. This is a new nanofabrication method for high-efficiency polarizers using small-sized wires, a double-wire grid configuration, and transparent substrates.
These innovative ultra-transparent and flexible polarizers could be applied in many different fields, such as security screening (to uncover concealed weapons or objects), medical imaging of superficial or soft tissues, quality control in manufacturing processes and ultrafast data communications.