The present invention provides an apparatus for a one-way waveguide and/or a circular polarizer that includes a waveguide having a height, a width, a length and a wave propagation direction. A first wall of the waveguide has a first slanted groove. A second wall opposite the first wall of the waveguide has a second slanted groove. The first and second grooves are rotated clockwise around the wave propagation direction to approximate a helical groove. The present invention may also include a third slanted groove in a third wall adjacent to the first wall and second wall, a fourth slanted groove in a fourth wall opposite the third wall, and the first, second, third and fourth grooves are rotated clockwise around the wave propagation direction to approximate the helical groove.