Reference to:
Optical transmission range on different wavelengths
and
Electrical characteristics at different frequencies.
QUARTZ or SILICA?
Guidelines for selecting wafer substrate material.
Fused Quartz & Fused Silica optical and electric properties are similar but differences do exist due to their difference in thermal characteristics and chemical composition. It is advisable to review those parameters in the Optical Properties and the Electrical Properties section of this web site in order to select the appropriate wafer substrate material.