Duration: 18 months
We propose to build a prototype of an infrared spectral filter using a novel thin film structure composed of layers of silicon and air, known as Distributed Bragg Reflector (DBR). This type of structure offers superior reflector, as silicon and air have very large difference in their respective refractive indices. This means the reflectivity is high and the operational range broad in the wavelength domain, as DBR reflectivity is determined by the difference of refractive indices of the DBR layers. VTT has experimented with these Bragg reflectors, but never for space or imaging applications. This type of reflector is highly beneficial for short or mid-wave infrared hyperspectral imaging applications, potentially addressing current system limitations such as limited operational range, poor reflectivity or unwanted absorption. Our goal is to manufacture a prototype of a tunable spectral filter (Fabry-Perot Interferometer) with a large optical aperture suitable for hyperspectral imaging (approximately 10-15 mm). The interferometer reflectors will be made with the proposed Si-Air structure. The spectral filter prototype will operate in the SWIR (1.5 - 2.5 um) or MWIR (2.5 - 5.0 um) range, with the exact wavelength range determined during the activity. The spectral filter concept design will be based on existing solutions, allowing us to focus our research efforts on manufacturing process of the Si-Air structure. All work will be conducted using VTT's internal facilities. If successful, this type of reflector could significantly enhance the performance of many infrared optical sensing applications, not just hyperspectral imaging.
