A firm seeks to identify spectral filter technologies to operate within a demanding optical environment. The technology solution will enable the suppression of out-of-band wavelengths above 100 nm, while exhibiting minimal loss to wavelengths of the order of 10 nm. The solution can be manufactured pinhole-free with an optical aperture of 180-200 mm in diameter. Structure and dimensions must be resilient to rapid thermal cycling over a prolonged period, and the solution would preferably be freestanding, i.e. not supported by a secondary layer. A supporting grid may be considered.