Self-Blocking SWIR Filters
Dec 2011Optics Balzers AGRequest Info
BALZERS, Liechtenstein, Dec. 21, 2011 — Optics Balzers AG offers customized bandpass filters with a self-blocking filter design for the short-wavelength infrared (SWIR) spectral region. They combine a wide blocking range and high bandpass transmittance in a single all-dielectric interference coating. All filters are deposited by in situ monitored plasma-assisted sputter and evaporation processes and show high stability in terrestrial and space environments. The company also offers compatible broadband dichroic beamsplitters.
SWIR optical sensing applications in the spectral region between 900 and 3000 nm require filters with high transmittance in the passband, blocking ranges over the full detector response and long-term shift-free spectral performance with good environmental stability. Applications include optical remote sensing of the Earth from air and space; near-infrared, Raman and emission spectroscopy; plasma diagnostics; blood analysis; and atmospheric greenhouse gas monitoring.
Within the sensitivity region of mercury cadmium telluride and InGaAs detectors, the selection and blocking of radiation by the filter can be provided by a single all-dielectric multilayer system. The self-blocking filter inhibits interference of multiple reflections in the filter substrate. Both bandpass and blocking are realized on one side of the substrate. The design facilitates deep-cooled detector array assemblies, where no color glasses and no cemented components are applicable.
The hard, all-dielectric coatings retain their optical properties after the vacuum process, even under various ambient conditions. They withstand temperatures from −100 to 300 °C, elevated humidity conditions and, in combination with selected substrate materials, gamma and proton radiation loads.
For production of SWIR filters, the company uses broadband spectra photometric thickness monitoring for optical checking of the layer characteristics during deposition. The accuracy of the monitoring and control technology ensures stable and repeatable coating results.