Abstract: A technique is presented to extract electromagnetic radiation from a dielectric loaded waveguide consisting of a layer or layers of dielectric material enclosed in a metallic conducting jacket. The electromagnetic radiation generated in the dielectric waveguide by a charged particle beam or otherwise generated as input to the waveguide. Dielectric loaded waveguides used for generation (or transport) of electromagnetic radiation at frequencies above 100 GHz have dimensions in the sub-mm range. Due to difficulty in the fabrication of a conventional broadband horn-like antenna to extract electromagnetic radiation from the structure because of the large impedance mismatch between the dielectric loaded waveguide and free space, the designing and fabricating aperture of antennas are formed as part of the dielectric waveguide and utilizes an angle cut or a set of apertures machined into the dielectric loaded waveguide to ensure broadband power extraction with minimal return loss and high directivity.