title: Precision Interferometric Measurements of Mirror Birefringence in High-Finesse Optical Resonators.
abstract: High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings. Strictly speaking, however, the optical coatings are often non-uniformly stressed during the deposition process and therefore do possess some small amount of birefringence. When physically mounted the cavity mirrors can be additionally stressed in such a way that large optical birefringence is induced. Here we report a direct measurement of optical birefringence in a two-mirror Fabry-Pérot cavity withR= 99.99 % by observing TEM00mode beating during cavity decays. Experiments were performed at a wavelength of 4.53μm, with precision limited by both quantum and technical noise sources. We report a splitting ofδν= 618(1) Hz, significantly less than the intrinsic cavity linewidth ofδcav≈ 3 kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore Δn/n= 6.38(1) × 10-6.
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Fleisher
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: David A
authors.initials: DA
authors.lastname: Long
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Qingnan
authors.initials: Q
authors.lastname: Liu
authors.affiliation: National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Hodges