All-dielectric bandpass filters from Optics Balzers Jena are for the SWIR (short wave infra red) spectral region and have a self-blocking filter design. They combine a wide blocking range and high pass-band transmittance in a single, all-dielectric interference coating. Potential application fields are optical remote sensing of the earth from air and space, greenhouse gas monitoring or plasma diagnostics and emission spectroscopy analysis. Within the sensitivity region of the mercury cadmium telluride or indium GaAs detectors, the selection and blocking of radiation by the filter can be provided by a single, all-dielectric, multi-layer system. This self-blocking filter design inhibits interference of multiple reflections in the filter substrate. Both bandpass and blocking are realised on one side of the substrate. This design approach facilitates deep-cooled detector array assemblies, where no colour glasses and no cemented components are applicable. The coatings will retain optical properties after the vacuum process, even under different ambient conditions, claims the company. They withstand temperatures from -100 to 300°C, elevated humidity conditions and gamma and proton radiation loads. To separate the SWIR detection band from other visible and near-IR receiving channels, the company also delivers broadband, dichroic beamsplitters.
