[en] Si:H alloys are being investigated for the high index material in an interference filter to provide spectral control in an application of thermophotovoltaic energy conversion. In particular, a multilayer edge filter is being developed to provide high transmission of photons with wavelengths between 1.0 and 2.0 (micro)m, and high reflectance for wavelengths outside this range. Thin films of Si:H were deposited by dc reactive sputtering. Deposition parameters were varied to optimize H content in Si: H coatings such that the refractive index is greater than 3, and optical absorption near 1 (micro)m and Si-H infrared absorptions near 5 and 12 (micro)m were minimized

[en] The optical properties of sputter deposited hafnium fluoride films and their use in fabricating a front surface, interference filter for thermophotovoltaic energy conversion (TPV) were investigated. In particular, HfF4 films were being considered for the low index component in a multilayer interference filter that will selectively transmit photons in the wavelength range of 1.0 micro m to 2.4 micro m, and strongly reflect all other wavelengths