Radial gradient-index glass prepared by the sol-gel process

Radial gradient-index glass has been prepared by the sol-gel process using tetrabutoxytitanium as the source of index- modifying cation. Two systems have been studied. Wet gels were obtained by first partially hydrolyzing tetraethoxysilane (TEOS), then adding tetrabutoxytitanium alone or together with Y(NO3)3 into the mixture and using another part of water to hydrolyze the salts thoroughly and make it gel. The wet gels were then put into a H2SO4 bath to partially leach out the index-modifying cations and form the concentration gradient. Through drying and sintering the gels were turned into transparent and colorless glass rods of about 4.5∼7.5 mm in diameter. The resulting refractive index profile of the glass has been measured and the maximum index change from the center to the perimeter was about 0.03.