Employing frequency-selective surface technology, the metal-mesh, band pass filters are designed with patterned, cross-shaped, and other resonant opening geometries that allow the transmission of light at specific wavelengths. Intended for cryogenic temperature applications, the filters have been supplied with center wavelengths (CWLs) of 24.4, 33.4, and 38.8 µm for use in an airborne telescope application. In that application, they have CWL transmissions up to 85 percent, CWL tolerance of ±0.1 µm, and out-of-band transmission down to 0.5 percent. The filters exhibit excellent thermal properties with stable and repeatable performance down to 4K. Their 1 mm thickness enables entry into existing filter wheels, cryostats, and compact optical instruments.
Lake Shore Cryotronics Inc., (614) 891-2244

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