The birefringence of a low-loss, high-reflectance coating applied to an 8-cm-diameter sapphire crystal grown in the m-axis direction has been mapped. By monitoring the transmission of a high-finesse Fabry–Perot cavity as a function of the polarization of the input light, we find an upper limit for the magnitude of the birefringence of 2.5 × 10-4 rad and an upper limit in the variation in direction of the birefringence of 10 deg. These values are sufficiently small to allow consideration of m-axis sapphire as a substrate material for the optics of the advanced detector at the Laser Interferometer Gravitational Wave Observatory.
© 2001 Optical Society of America
Original Manuscript: January 19, 2001
Revised Manuscript: April 10, 2001
Published: August 1, 2001
Jordan B. Camp, William Kells, Martin M. Fejer, and Eric Gustafson, "Measurement of birefringence of low-loss, high-reflectance coating of m-axis sapphire," Appl. Opt. 40, 3753-3758 (2001)