Optimization of THz diffractive optical elements thickness

Abstract

Diffractive optical elements (DOEs) are strictly related to the design wavelength due to the fact that they must introduce particular phase delay of the wavefront propagating through the structure. Mostly the attenuation of the material is not taken into account. In this article we propose to optimize thickness of the DOE by reducing introduced phase retardation but also attenuation. The efficiency of DOEs is determined by the method of coding phase distribution and can be easily measured by using diffraction orders of corresponding diffraction grating. Here, we analyze binary phase diffraction gratings with assumed attenuation. Full Text: PDF ReferencesJ.-L. Coutaz, Optoélectronique térahertz (Les Ulis CEDEX A, France, EDP Sciences 2012). DirectLink D. Headland, Y. Monnai, D. Abbott, C. Fumeaux,and W. Withayachumnankul, "Tutorial: Terahertz beamforming, from concepts to realizations", APL Photonics 3, 5 (2018). CrossRef S. F. Busch, M. Weidenbach, M. Frey, F. Schäfer, T. Probst, nd M. Koch, "A 3D-Printable Polymer-Metal Soft-Magnetic Functional Composite—Development and Characterization", Journal of Infrared, Millimeter, and Terahertz Waves 35, 12 (2014) CrossRef A. Siemion, P. Kostrowiecki-Lopata, A. Pindur, P. Zagrajek, M. Sypek, "Paper on Designing Costless THz Paper Optics", Advances in Materials Science and Engineering 2016, 9615698 (2016). CrossRef A. Siemion, A. Siemion, M. Makowski, J. Suszek, J. Bomba, A. Czerwinski, F. Garet, J.-L. Coutaz, and M. Sypek, "Diffractive paper lens for terahertz optics", Opt. Lett. 37, 4320–4322 (2012). CrossRef J.-L. Coutaz, F. Garet, E. Bonnet, A. V. Tishchenko, O. Parriaux, and M. Nazarov, "Grating Diffraction Effects in the THz Domain", Acta Phys. Pol. A 107, 26-37 (2005). CrossRef M. S. Heimbeck, P. J. Reardon, J. Callahan, and H. O. Everitt, "Transmissive quasi-optical Ronchi phase grating for terahertz frequencies", Opt. Lett. 35, 21 (2010). CrossRef D. Li, S. Shu, F. Li, G. Ma, Y. Dai, and H. Ma, "Anomalous transmission of terahertz wave through one-dimensional lamellar metallic grating", Opt. Commun. 284, 10-11 (2011). CrossRef X. Li, and S. F. Yu, "Diffraction Characteristics of Concentric Circular Metal Grating Operating at Terahertz Regime", IEEE Journal of Quantum Electronics 46, 6 (2010). CrossRef B. Nöhammer, C. David, J. Gobrecht, and H. P. Herzig, "Optimized staircase profiles for diffractive optical devices made from absorbing materials", Opt. Lett. 28(13), 1087-1089 (2003). CrossRef V. Deuter, M. Grochowicz, S. Brose, J. Biller, S. Danylyuk, T. Taubner, D. Grutzmacher, and L. Juschkin, "Holographic masks for computational proximity lithography with EUV radiation", International Conference on Extreme Ultraviolet Lithography 2018 10809, 108091A (2018). CrossRef J. W. Goodman, Introduction to Fourier optics (Greenwood Village, USA, Roberts & Company Publishers 2005). DirectLink W. B. Veldkamp, "Optimized staircase profiles for diffractive optical devices made from absorbing materials", Appl. Opt. 21(17), 3209-3212W (1982). CrossRef W. B. Veldkamp, and C. J. Kastner, "Beam profile shaping for laser radars that use detector arrays", Appl. Opt. 21(2), 345-356 (1982). CrossRef https://www.mcortechnologies.com/de/3d-drucker/mcor-iris/ DirectLinkM. Sypek, M. Makowski, E. Hérault, A. Siemion, A. Siemion, J. Suszek, F. Garet, and J.-L. Coutaz, "Highly efficient broadband double-sided Fresnel lens for THz range", Opt. Lett. 37, 12 (2012). CrossRef

Impact of fabrication errors and refractive index on multilevel diffractive lens performance

“…First, the ease in modelling larger unit cells ("rings") leads to the total number of elements in the entire structure to be small and tractable; hence, it is easy to capture the trade-off in efficiency with faster simulations and develop accurate prediction metrics. Therefore, the THz regime is an ideal frequency band to capture the real significance of this work 44,45 . Second, since the THz band lies in almost the centre of the electromagnetic spectrum, hence the metrics developed in this paper can be scaled up or down to both the microwave as well as optical ranges without any loss of generality.…”

The Magic of Optics—An Overview of Recent Advanced Terahertz Diffractive Optical Elements

“…Many different 3D printed materials were analyzed due to the simplicity and accessibility of manufacturing DOEs for THz range. Moreover, the direct 3D printing of all metal terahertz components has also been demonstrated in the literature [55,56]. In the context of the described issues, it is important that in THz range there is a whole variety of different materials suitable to manufacture optics.…”

“…Many different 3D printed materials were analyzed due to the simplicity and accessibility of manufacturing DOEs for THz range. Moreover, the direct 3D printing of all metal terahertz components has also been demonstrated in the literature [ 55 , 56 ].…”

“…Such a procedure is used in the case of UV optics when the structure thickness is thinner than the value calculated from the diffractive optics assumption [ 23 ]. It introduces a smaller phase shift but also according to Beer-Lambert’s law—attenuates less which can be also used for THz range [ 56 ].…”

“…In the case of high-attenuating materials, the total efficiency can be larger for the grating with smaller phase shift but also smaller thickness. Both these values can be optimized to provide as large efficiency as possible for a particular grating type and used material [ 23 , 56 ]. Changing grating height was also used in the reflection grating to modify the ratio of intensities redirected between 0th and ±1st orders [ 103 ] by a set of gratings with different step heights.…”