20 February 2015 Realization of spiral phase plates by 3D lithography
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Proceedings Volume 9258, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VII; 92581S (2015) https://doi.org/10.1117/12.2072178
Event: Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies 2014, 2014, Constanta, Romania
In this paper we will present two technological processes necessary to experimentally obtain diffractive optical elements (DOE) operating in reflection which generate optical beams presenting orbital angular momentum. This class of DOE, also known as spiral phase plates (SPP), are three-dimensional structures consisting in disks where the variation of their thickness is directly proportional with the azimuthal angle Φ. In this case a beam of light applied on the SPP surface acquires an angular orbital momentum (OAM) and a vortex – like configuration. The first technique is the 3D electron beam lithography (EBL). The materials utilized in this case are the positive electronresist PMMA 35 K which has a deposition thickness of 500 nm and the negative electronresist SU8. To obtain the three dimensional structure, the PMMA and SU-8 films were configured by different exposure doses such that after development process each exposure corresponds to a defined thickness of the electronresist. The calibration curve between exposure dose and the height of the structure was determined. The second technique investigated here is photolithography. In this case a photoresist layer was exposed through a mask presenting regions with various levels of transmittance in order to obtain different levels of heights.
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Roxana Tomescu, Roxana Tomescu, Adrian Dinescu, Adrian Dinescu, Dana Cristea, Dana Cristea, Mihai Kusko, Mihai Kusko, Raluca Gavrila, Raluca Gavrila, Cristian Kusko, Cristian Kusko, "Realization of spiral phase plates by 3D lithography", Proc. SPIE 9258, Advanced Topics in Optoelectronics, Microelectronics, and Nanotechnologies VII, 92581S (20 February 2015); doi: 10.1117/12.2072178; https://doi.org/10.1117/12.2072178

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