Low expansion transparent glass-ceramics, glass-ceramic substrate and optical waveguide element

摘要

There are provided low expansion transparent glass-ceramics obtained by heat treating a base glass produced at a relatively low melting temperature of 1530° C. or below. The glass-ceramics have an average linear thermal expansion coefficient within a range from +6×10⁻⁷/° C. to +35×10⁻⁷/° C., 80% transmittance wavelength (T₈₀) of 700 nm or below, internal transmittance of 75% or over at light wavelength of 1550 nm, heat resisting temperature of 800° C. or over and Young's modulus of 90 GPa or over. The glass-ceramics comprise SiO₂, Al₂O₃, MgO, CaO, BaO, ZnO, Li₂O, TiO₂ and ZrO₂ and contain β-quartz or β-quartz solid solution as a predominant crystal phase. There are also provided optical waveguide elements and an arrayed waveguide grating (AWG) type planar lightwave circuit utilizing these glass-ceramics.