Patent ID: 8828550

Claim:
A dopant host comprising a laminate comprising a boron component volatilization layer comprising 30 to 60 mol % of SiO 2 , 10 to 30 mol % of Al 2 O 3 , 15 to 50 mol % of B 2 O 3 , and 2 to 15 mol % of RO where R is an alkaline earth metal, and a heat resistant layer comprising 8 to 40 mol % of SiO 2 , 40 to 85 mol % of Al 2 O 3 , 5 to 30 mol % of B 2 O 3 , and 0.5 to 7 mol % of RO where R is an alkaline earth metal, at least one outermost layer of the laminate being composed of the boron component volatilization layer, the laminate further comprising the boron component volatilization layer inside the laminate, the boron component volatilization layer constituting at least one outermost layer of the laminate having a B 2 O 3 content lower than a B 2 O 3 content in the boron component volatilization layer inside the laminate.