1Bremer Institut für angewandte Strahltechnik GmbH (Germany) 2Aswan Univ. (Egypt) 3Philipps-Univ. Marburg (Germany) 4Ctr. de Investigaciones en Optica, A.C. (Mexico) 5Univ. of Bremen (Germany)
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We propose a new solution for sensing a terahertz (THz) wavefront based on a THz reference-less shear interferometer. The key component of the experimental configuration of the proposed interferometer is a THz Ronchi phase grating (RPG). The RPG is custom designed and fabricated for a 0.28 THz source using mechanical milling on a block of high-density polyethylene (HDPE) with a computer numerical control (CNC) machine. It acts as a shearing element that generates two diffraction orders, thereby creating two laterally shifted copies of the investigated wavefront in the sensor plane where a THz camera is placed. The direction of the shear can be varied by rotating the grating. Since the grating is a phase grating, the diffraction efficiency is very high. The approach is verified experimentally by demonstrating interferograms of a spherical wave and wavefront reconstruction from five different shears using a gradient-based iterative process.
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Mostafa Agour, Claas Falldorf, Fatima Taleb, Enrique Castro-Camus, Martin Koch, Ralf B. Bergmann, "Shear interferometry for terahertz wavefront sensing," Proc. SPIE 12134, Terahertz Photonics II, 121340B (31 May 2022); https://doi.org/10.1117/12.2621696