Tunable Freestanding THz Bandpass Filters with Stable Optical Performance from 0.3 to 1.6 THz

Metal mesh filters play a crucial role in far-infrared (IR) and terahertz (THz) applications, offering noise reduction and enhanced detector performance. They are widely used in space-based astronomy, high-altitude observations, and sensing technologies. Despite their advantages, conventional filters are typically passive elements with fixed properties, which require complex fabrication processes. Many applications, however, demand tunability over a broad frequency range while maintaining a high performance. In this work, we present tunable THz filters manufactured with a highly reproducible laser structuring method. The filters are characterized with a THz TDS system. Experimental results show an excellent agreement with simulations in terms of key performance values such as high transmission at the bandpass frequency (85-90%) and out of band blocking (<5%) within a broad range (0.3-1.6 THz).