Resonantly Enhanced Axion-Photon Regeneration

Photon-regeneration experiments which search for the axion, or axionlike particles, may be resonantly enhanced by employing matched Fabry-Perot optical cavities encompassing both the axion production and conversion magnetic field regions. Compared to a simple photon-regeneration experiment, which uses the laser in a single-pass geometry, this technique can result in a gain in rate of order F², where F is the finesse of the cavities. This gain could feasibly be 10^{(10 12)}, corresponding to an improvement in sensitivity in the axion-photon coupling g_aγγ of order F^1/2∼10^{(2.5 3)}, permitting a practical purely laboratory search to probe axion-photon couplings not previously excluded by stellar evolution limits or solar axion searches.