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Precision Interferometric Measurement of Mirror Birefringence in High-Finesse Optical Resonators



Adam J. Fleisher, David A. Long, Qingnan Liu, Joseph T. Hodges


High-finesse optical resonators found in ultrasensitive laser spectrometers utilize supermirrors ideally consisting of isotropic high-reflectivity coatings with power reflectivity $R\geq99.99\%$. 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-P\'{e}rot cavity with $R=99.99\%$ at a wavelength of 4.53 $\mu$m by observing TEM$_{00}$ mode beating during passive cavity decays with noise limited by both quantum and technical sources. We report a splitting of $\delta_{\nu}=618(1)$ Hz, significantly less than the intrinsic cavity linewidth of $\delta_{\text{cav}}\approx3$ kHz. With a cavity free spectral range of 96.9 MHz, the equivalent fractional change in mirror refractive index due to birefringence is therefore $\Δ n/n=6.38(1)\times10^{-6}$.
Physical Review A


Fleisher, A. , Long, D. , Liu, Q. and Hodges, J. (2016), Precision Interferometric Measurement of Mirror Birefringence in High-Finesse Optical Resonators, Physical Review A, [online], (Accessed May 22, 2024)


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Created January 19, 2016, Updated November 10, 2018