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Thick THz metamaterials fabricated by 3D printer for THz high-pass filter application

Terahertz (THz) technologies have been gaining a great deal of interests, but current THz optics is still facing various challenges in their functionality and performance. Metamaterials, which are artificial structures consisting of many periodical units smaller than the wavelength of electromagnetic waves, are attracting attention as a new tool for the development of THz optics because the optical properties of metamaterials can be controlled by appropriate structures. However, lithography techniques conventionally used to make metamaterials can only make quasi-two-dimensional thin-film structures with thicknesses much smaller than the wavelength of THz waves (typically several hundred micrometer). This is a serious limiting factor, as the three dimensionality of the structure is important to extend the functionality of metamaterials as optical components [1]. Recently, the 3D printer has gained attention as a means to fabricate 3D metamaterial because there is, in principle, no limitation to achievable thickness [2]. However, the typical resolution necessary to make THz metamaterial is smaller than several hundred micrometers, and this is still challenging for conventional metal 3D printers. In order to overcome this difficulty, we have developed a new 3D printing technology which can make metallic structures with sufficient resolution for making THz metamaterial. As a demonstration to show the advantage of our technology, we made a “thick” THz metamaterial with 1-mm thickness, which is larger than the typical THz wavelength. This device works as high-pass filter with a sharp cut-off frequency because of the thick characteristic. This presented 3D printing technology, enables to make 3D THz metamaterials without thicknesses limitation, and should bring innovation to the field of development of THz optics.