Subterahertz refractive flat-top beam shaping via 3D printed aspheric lens combination

The viability of 3D printed aspheric lenses for the purpose of frequency-scalable subterahertz Gaussian to flat-top beam shaping is evaluated. A cylindrical one-dimensional Fresnel–Kirchhoff diffraction equation was implemented in Matlab and used to design a pair of aspheric lenses with customized vertex radius of curvature and conic constant. The lenses were printed at maximum possible resolution in acrylonitrile butadiene styrene ( n = 1.6 ) and tested with a 102 GHz continuous-wave subterahertz source. The aspheric lens combination produced a flat-top profile from a low-quality incident Gaussian beam at the minimal cost of 3D printing substrate. The flat-top profile exhibited small ( < 14 % root-mean-square deviation over a flat region) intensity fluctuations and is expected to prove useful in future terahertz applications that require a high degree of beam uniformity.