We have developed an apparatus to test Lorentz invariance in the photon
sector by measuring the resonant frequency difference between two
counterpropagating directions of an asymmetric optical ring cavity using a
double-pass configuration. No significant evidence for the violation was found
at the level of δc/c≲10−14. Details of our apparatus and
recent results are presented.Comment: 4 pages, 1 figure. Presented at the Sixth Meeting on CPT and Lorentz
Symmetry, Bloomington, Indiana, June 17-21, 201