Image Number 4 for United States Patent #4175830.
Mode converter for electromagnetic, light or infrared waves. This mode converter converts particle non-confining modes to particle confining modes. In a confining mode wave beam the phase of the wave with respect to time at a point of the beam having a given azimuth with respect to the beam axis is proportional to this azimuth. Two types of mode converter are disclosed. In the first type, the wave passes through a block of transparent isotropic material the thickness of which is proportional to the azimuth around the beam axis. In the second type, the converter is formed with triangular or sectoral plates of birefringent material and in each plate the slow and fast axes are given an adequate orientation.