Patent ID: 7648648

Claim:
An anti-Stokes fluorescent composition comprising M, ytterbium, thulium, oxygen, and sulfur in a molar ratio relative to each other corresponding to the following formula: (M x , Yb y , Tm z ) 2 O 2 S wherein M is selected from the group consisting of yttrium, gadolinium, and lanthanum; x+y+z=1; x>0; y>0; and z is from 0.0025 to 0.03, said composition having a fluorescence that, when subjected to IR radiation having a wavelength of 975 nm, (a) emits IR light having a wavelength of 796 nm with an intensity I 796 nm , and (b) emits visible blue light having a wavelength of 480 nm with an intensity I 480 nm , wherein I 796 nm is expressed as a percentage of the intensity of IR light emitted from a reference composition consisting of Y 1.524 Yb 0.474 Tm 0.0018 O 2 S when said reference composition is subjected to IR radiation having a wavelength of 975 nm; wherein I 480 nm is expressed as a percentage of the intensity of visible blue light emitted from a reference composition consisting of Y 1.524 Yb 0.474 Tm 0.0018 O 2 S when said reference composition is subjected to IR radiation having a wavelength of 975 nm; and wherein I 480 nm is less than 45% of said I 796 nm .