Opt. Lett. 36, 3572–3574 (2011)

Optical cavities are essential to the operation of atomic clocks, where they enable high-resolution spectroscopy and provide short-term stability during interrogation of the atomic transition. Because the lasing frequency of a cavity is defined by its length, any vibration- or inertia-induced length perturbations must be minimized to achieve spectral purity. Now, Stephen Webster and Patrick Gill at the National Physical Laboratory in the UK have designed a rigidly mounted cubic optical cavity that is insensitive to both inertial and compressive forces. Their design is based on a cubic geometry with four supports placed symmetrically about the optical axis in a tetrahedral configuration. The researchers measured the inertial force sensitivity of their device by locking a laser to the cavity while simultaneously inverting it about three orthogonal axes. They measured a maximum acceleration sensitivity of 2.5 × 10−11 g−1, which is the lowest ever passive sensitivity reported for an optical cavity. The researchers say that the sensitivity may be reduced even further through the use of active feed-forward correction.