Serrated Edge Design and Field Analysis in Spatial, Time, and Angular Domains for Improving the Field Uniformity of Beam Combiner

Abstract

Edge diffraction of a beam combiner will adversely affect the field uniformity in the observation plane. In order to suppress the edge diffraction, the serrated edge design method is proposed. According to the equivalence principle, a field uniformity analysis method was proposed to compute the spatial field distribution radiated from the aperture of a beam combiner. In order to separate the direct wave from diffracted wave, the spatial field is transformed into the time- and angular-domain spectrum by inverse Fourier transform. First, the height of serrations is designed by analog of the equivalent trapezoidal amplitude taper. Then, the number of serrations was designed by the assumption of isosceles and right triangles. Finally, the shape of serrations was designed by changing the interior angle of serrations. A serrated edge design example is also proposed and analyzed. By comparing the field uniformity in spatial, time, and angular domains before and after serrating the edges, the amplitude and phase ripples decrease from 1.85 dB and 12.16° to 0.53 dB and 3.98°, respectively. The results show that the field uniformity is significantly improved.