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Albert J. Sievers received the APS Frank Isakson Prize in 1988 for his "innovative and imaginative use of infrared and far infrared radiation in determining the fundamental optical properties of solids, defects and surfaces." In 1999 he received the Institute of Physics (London) Kenneth John Button Prize "for outstanding contributions to research in the field of far-infrared physics." His early work concerned FFT spectroscopy and He-3 cooled detector development resulting in pioneering far infrared spectroscopic studies of condensed matter systems. Together with N. Bloembergen he identified early on the new properties of photonic bandgap materials. With studies of thermal radiation he demonstrated for the first time the minimum thermal radiation possible from metal surfaces over a broad temperature range. He then turned to the far infrared studies of both small metal particles and bulk metals, including extensive work on bismuth and on high pressure, low temperature and high magnetic field effects. In many cases he and his collaborators developed new technologies with which to carry out their studies. Sievers used both coherent and incoherent sources to conduct mid-infrared and far-infrared studies of localized vibrational modes in solids, of adsorption of molecules on metal surfaces and made the first measurements of the frequency dependent carrier mass of valence fluctuation and of heavy fermion systems. In 1982 he and his colleagues discovered the process of persistent IR spectral hole burning in the vibrational modes of molecules in solids and in 1984 he and his students developed the first solid state IR vibrational laser. The exploration of defect modes provided the foundation for the 1988 proposal by Sievers and Takeno that nonlinearity plus lattice discreteness could give rise to energy localization in the noncontinuum limit for perfect crystals. This realization has led to extensive studies of the features associated with intrinsic localization in various kinds of nonlinear lattices by researchers the world over, and it has proven to be a conceptual and practical breakthrough.