Design and fabrication of terahertz Dammann grating

Hao Lin; He Ma; Lu Rong; Yunxin Wang; Jie Zhao; Shufeng Lin; Xinping Zhang; Dayong Wang

doi:10.1117/12.2666967

27 January 2023 Design and fabrication of terahertz Dammann grating

Hao Lin, He Ma, Lu Rong, Yunxin Wang, Jie Zhao, Shufeng Lin, Xinping Zhang, Dayong Wang

Proceedings Volume 12550, International Conference on Optical and Photonic Engineering (icOPEN 2022); 125502F (2023) https://doi.org/10.1117/12.2666967
Event: International Conference on Optical and Photonic Engineering (icOPEN 2022), 2022, ONLINE, China

Abstract

Based on the diffraction propagation mechanism of terahertz waves and the basic theory of binary optics, transmission terahertz Dammann gratings is designed, fabricated, and characterized for the working wavelength of 2.52THz. The simulated annealing algorithm is used to design the phase structure of a 2D terahertz Dammann gratings which can generate 2×2 and 6×6 diffraction beams. MATLAB is used to conduct diffraction beam splitting simulation of the designed Dammann grating. The simulation results show that the 2D diffraction efficiency of the grating reaches around 60 %, and the unevenness of the split sub-spots is controlled below 1%. During the grating fabrication process, N-type high-resistivity silicon (n = 3.4175 @ 2.52 THz) is used as the grating material, and silicon nitride (Si3N4) with 200nm thickness is used as the hard mask layer. To achieve extremely high etching depths, the wet deep silicon etching process of potassium hydroxide (KOH) solution is used as the fabrication process. Various pivotal process parameters, such as the initial concentration of each component, are optimized through many experiments. The etching depth of the order of 50 μm is achieved. The grating surface flatness and step sidewall steepness satisfy the needs of use. The characterization experiment results show that the 2D diffraction efficiency of the grating is about 50 %, and the unevenness is about 2.5 %, which basically verifies the reliability of the design theory and fabrication process.

Citation Download Citation

Hao Lin, He Ma, Lu Rong, Yunxin Wang, Jie Zhao, Shufeng Lin, Xinping Zhang, and Dayong Wang "Design and fabrication of terahertz Dammann grating", Proc. SPIE 12550, International Conference on Optical and Photonic Engineering (icOPEN 2022), 125502F (27 January 2023); https://doi.org/10.1117/12.2666967

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