Patent ID: 8763430

Claim:
A method for manufacturing a GRIN lens, comprising: a step of producing a wet gel from an alcohol solution containing a silicon alkoxide, a dopant alkoxide, and a boron alkoxide as the main ingredients having a concentration of a boron simple substance of 1 to 15 mol % relative to that of a silicon simple substance, a dopant simple substance, and a boron simple substance; a step of eluting a dopant simple substance and a boron simple substance from an outer surface of the wet gel by leaching to give a refractive index distribution and to give the wet gel increased porosity by eluting almost all the boron; a step of drying the wet gel to produce a dry gel having a decreased bulk density equal to or less than 0.830 (g/cm 3 ); a step of sintering the dry gel to form a glass base material; and a step of drawing the base material, wherein the concentration of the boron simple substance remaining in the dry gel after leaching is lower than 0.1 mol % relative to that of a silicon simple substance, the dopant simple substance, and the boron simple substance.