In this talk I will present a novel technique for the astrophysical detection of axions or axion-like particles in the dark matter halo of the Milky Way based on stimulated decay of axions. Photons from the brightest known radio sources with a frequency equal to half the axion mass stimulate axion decay while propagating through the dark matter halo, causing radio emission in the direction and precisely opposite to the incoming photon in the axion rest-frame. This effect should create a countersource for every radio source in the sky. In the talk I will show the result for the countersource of Cygnus A, the brightest extragalactic radio source, and the limits that can be set with SKA to the axion-photon coupling constant.

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