The optical performance of frequency selective bolometers
  Frequency Selective Bolometers (FSBs) are a new type of detector for millimeter and sub-millimeter wavelengths that are transparent to all but a narrow range of frequencies as set by characteristics of the absorber itself. Therefore, stacks of FSBs tuned to different frequencies provide a low-loss compact method for utilizing a large fraction of the light collected by a telescope. Tests of prototype FSBs, described here, indicate that the absorption spectra are well predicted by models, that peak absolute absorption efficiencies of order 50% are attainable, and that their out-of-band transmission is high. 
T. A. Perera, T. C. Chen, E. S. Cheng, D. A. Cottingham, T. M.   Crawford, T. P. Downes, F. M. Finkbeiner, D. J. Fixsen, D. ...