Maser mechanism of optical pulsations from anomalous X-ray pulsar   4U0142+61
  A maser curvature emission mechanism in the presence of curvature drift is used to explain the optical pulsations from anomalous X-ray pulsars. For the source of AXP0142+61,the optical pulsation occurs at the radial distance $R(\nu_M)\sim 4.75\times 10^9$ cm to the neutron star. The corresponding curvature maser frequency is about $\nu_M\approx1.39\times 10^{14}$ Hz. The result is consistent with the observation of the optical pulsations from the anomalous X-ray pulsar 4U0142+61. 
Y.LU, and S.N.Zhang