Optical inks suitable for 3D printing fabrication of gradient refractive index (GRIN) optical components are composed of a monomer matrix material [100] in which ligand-functionalized nanoparticles [102] are well dispersed at more than 2% loading to induce a change in the index of refraction of the matrix of at least 0.02. The ligands are less than 1.2 nm in length and are covalently bonded to both the nanoparticles and the monomer matrix. The nanoparticles are less than 100 nm in size and the doped matrix material has a transmittance of at least 90% at wavelengths of interest. The matrix material has less than 20 cPoise viscosity and is UV crosslinkable to form a cured polymer.