Fabrication process of a gradient index type of optical element

A process of fabricating a gradient index optical element, comprising:

• obtaining a sol by hydrolysis of a silicon alkoxide with an acid and adding to a hydrolysis product a solution containing at least one metal salt selected from a second metal component group consisting of barium, lanthanum, yttrium, gadolinium, strontium, calcium, and zinc, and gelating said sol;
• dehydrating the wet gel, and dipping the wet gel in a solution containing an alkoxide of at least one metal component selected from a first metal group consisting of titanium, niobium, tantalum, and zirconium or a derivative thereof to thereby impart to the wet gel a concentration gradient with a concentration of a first metal component decreasing from a periphery to a center of the wet gel while, at the same time, the wet gel is dehydrated;
• and
• drying and firing the wet gel.

A process of fabricating a gradient index optical element, comprising the step of:

• dipping a wet gel prepared by gelation of a silicon component-containing sol in a solution containing at least one metal salt selected from a second metal component group consisting of barium, lanthanum, yttrium, gadolinium, strontium, calcium, and zinc to thereby obtain a wet gel in which said wet gel contains said metal salt;
• dipping the wet gel in a solution containing a metal alkoxide of at least one metal component selected from a first metal component group consisting of titanium, niobium, tantalum, and zirconium or a derivative thereof to thereby impart to the wet gel a concentration gradient with a concentration of a first metal component decreasing from a periphery to a center of the wet gel;
• eluting from the wet gel at least one metal salt selected from the second metal component group consisting of barium, lanthanum, yttrium, gadolinium, strontium, calcium, and zinc thereby to impart to the wet gel a concentration gradient with a concentration of the second metal component increasing the periphery to the center of the wet gel;
• and
• said process further comprising a step of dehydrating the wet gel before the wet gel is dipped in the solution containing a metal alkoxide of at least one metal component selected from the first metal component group consisting of titanium, niobium, tantalum and zirconium or a derivative thereof;
• drying and firing the wet gel.

A process of fabricating a gradient index optical element, comprising:

• obtaining a sol by hydrolysis of a silicon alkoxide with an acid and adding to a hydrolysis product a solution containing at least one metal salt selected from a second metal component group consisting of barium, lanthanum, yttrium, gadolinium, strontium, calcium, and zinc, and gelating said sol;
• dehydrating the wet gel by dipping the wet gel in a hydrophilic organic solvent containing a hydrator before dipping the wet gel in a solution containing an alkoxide of at least one metal component selected from a first metal component group consisting of titanium, niobium, tantalum, and zirconium or a derivative thereof;
• dipping the wet gel in a solution containing an alkoxide of at least one metal component selected from a first metal component group consisting of titanium, niobium, tantalum, and zirconium or a derivative thereof to thereby impart to the wet gel a concentration gradient with a concentration of a first metal component increasing and a concentration of a second metal component decreasing, from a periphery to a center of the wet gel;
• and
• drying and firing the wet gel.