Optical sensor materials, as follows: (a) Elemental tellurium (Te) of purity levels of 99,9995 % or more; (b) Single crystals (including epitaxial wafers) of any of the following: 1. Cadmium zinc telluride (CdZnTe) with zinc content of less than 6 % by ‘mole fraction’; 2. Cadmium telluride (CdTe) of any purity level; or 3. Mercury cadmium telluride (HgCdTe) of any purity level. Technical note: ‘Mole fraction’ is defined as the ratio of moles of ZnTe to the sum of the moles of CdTe and ZnTe present in the crystal.