1107.1712 (H. Tam et al.)

Detection of Axion-like Particles by Interferometry    [PDF]

H. Tam, Q. Yang

We propose an interferometry experiment for the detection of axion-like particles (ALPs). As in ordinary photon-regeneration (light shining through a wall) experiments, a laser beam traverses a region permeated by a magnetic field, where photons are converted to ALPs via the Primakoff process, resulting in a slight power loss and phase shift. The beam is then combined with a reference beam that originates from the same source. The detection of a change in the output intensity would signal the presence of ALPs (or possibly other particles that couple to the photon in a similar way). Because only one stage of conversion is needed, the signal is of ${\cal O}(g^2_{a\gamma \gamma})$, as opposed to ${\cal O}(g^4_{a\gamma \gamma})$ for photon-regeneration experiments, where $g_{a\gamma \gamma}$ is the coupling between ALPs and photons. This improvement over photon-regeneration is nullified by the presence of shot noise, which however can be reduced by the use of squeezed light, resulting in an improvement in the sensitivity to $g_{a\gamma\gamma}$ over ordinary photon-regeneration experiments by an order of $10^{1/2}$ assuming $10{\rm dB}$ noise suppression. Additionally, our setup can incorporate straightforwardly optical delay lines, boosting the signal by a factor of $n\sim10^3$, where $n$ is the number of times the laser beam is folded. This way, we can constrain $g_{a\gamma\gamma}$ better by yet another factor of $n^{1/2}\sim 10^{1.5}$, as compared to the $n^{1/4}$ boost that would be achieved in photon-regeneration experiments.

View original: http://arxiv.org/abs/1107.1712