19 February 2014 Subwavelength grating reflectors in MEMS tunable Fabry-Perot infrared filters with large aperture
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Proceedings Volume 8995, High Contrast Metastructures III; 89950I (2014) https://doi.org/10.1117/12.2040339
Event: SPIE OPTO, 2014, San Francisco, California, United States
This paper presents a novel tunable infrared filter applying a subwavelength grating that substitutes the distributed Bragg reflectors (DBRs) in tunable Fabry-Perot (FP) filters to reduce cost and fabrication effort. It consists of uniformly arranged disc resonators which are made of 100 nm thick aluminum at a 200 nm Si3N4 membrane carrier that stands freely after fabrication. The dimensions of the subwavelength structures were optimized based on finite difference time domain (FDTD) analysis. The fabrication sequence consists of silicon MEMS technology steps like deposition and patterning of electrodes and of isolation layers, silicon etching, and wafer bonding, and it includes nano imprint lithography for forming the subwavelength structures at wafer level. The samples have an aperture of 2 mm and are mechanically tuned by electrostatic forces with tuning voltages up to 80 V. They show the typical characteristics of FP filters but with high peak transmittance within a remarkably large wavelength range (T < 50% @ 2.5 μm … 6.5 μm) spanning over 5 interference orders of the optical resonator. The optical performance was measured by Fourier transform infrared spectrometer and compared to the simulation results. It shows a widely good agreement between calculation and measurement.
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Steffen Kurth, Steffen Kurth, Karla Hiller, Karla Hiller, Marco Meinig, Marco Meinig, Jan Besser, Jan Besser, Mario Seifert, Mario Seifert, Martin Ebermann, Martin Ebermann, Norbert Neumann, Norbert Neumann, Florian Schlachter, Florian Schlachter, Thomas Gessner, Thomas Gessner, "Subwavelength grating reflectors in MEMS tunable Fabry-Perot infrared filters with large aperture", Proc. SPIE 8995, High Contrast Metastructures III, 89950I (19 February 2014); doi: 10.1117/12.2040339; https://doi.org/10.1117/12.2040339

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