Membrane-based mesh filter for far-infrared radiation

Future space-based far-infrared instruments rely on optical components that enable high-efficiency observations in challenging environments. Here we demonstrate membrane-based mesh bandpass filters for far-infrared electromagnetic waves, targeting wavelengths of 15-37 μ m. The filter architecture consists of periodic in-plane patterns, combined with alternating layers of polyimide and gold stacked vertically. This design utilizes spatial in-plane degrees of freedom and the vertical structure of the filters to achieve the desired filter performance. The optimization of this architecture is performed using finite-element electromagnetic simulations, and the fabrication is realized using advanced micro-fabrication techniques. Experimental validation of fabricated filters via Fourier transform infrared (FTIR) spectroscopy demonstrates an 80 percent transmission efficiency. These membrane-based filters meets theoretical expectations, selectively transmits wavelengths, and are compatible with existing instrument architectures, making them a promising solution for far-infrared astronomy.