Experimental probes of axions
  Experimental searches for axions or axion-like particles rely on
semiclassical phenomena resulting from the postulated coupling of the axion to
two photons. Sensitive probes of the extremely small coupling constant can be
made by exploiting familiar, coherent electromagnetic laboratory techniques,
including resonant enhancement of transitions using microwave and optical
cavities, Bragg scattering, and coherent photon-axion oscillations. The axion
beam may either be astrophysical in origin as in the case of dark matter axion
searches and solar axion searches, or created in the laboratory from laser
interactions with magnetic fields. This note is meant to be a sampling of
recent experimental results.
