Description
Fabry-Pérot interferometers are widely used as narrowband spectral filters for wavelength discrimination, where the passband wavelength is determined by the optical cavity spacing between two highly reflective Distributed Bragg Reflectors (DBRs) and the passband is swept across wavelength ranges by varying that spacing. In the infrared spectral range, such devices are commonly fabricated using MEMS technology, in which two DBRs are separated by an optical cavity gap of only a few micrometres [1]. However, extending this approach to the terahertz spectral range is challenging because it requires depositing extremely thick DBR layers. Alternative approaches based on metamaterials remain in their early stages of development.
Here, we present a pathway towards actuated, 3D-printed Fabry-Pérot filters for the terahertz spectral range. The proposed devices are based on a large-area polymer filter architecture fabricated using low-cost fused deposition modelling 3D printing [2]. The filters employ polylactic acid layers as reflective elements, separated by air cavities that define the resonant transmission frequencies. Two mirrors, each formed using PLA-air-PLA DBR structures, are separated by a tuneable optical cavity.
In contrast to conventional MEMS-based Fabry-Pérot filters, tunability in the 3D-printed devices is achieved through electromagnetic actuation of the top DBR. A miniature permanent magnet attached to the movable 3D-printed reflector is displaced by a current-driven electromagnetic coil. This displacement changes the mirror separation and modifies the optical path length of the Fabry-Pérot cavity, thereby shifting the resonant transmission frequency across the terahertz spectrum. Compared with electrostatic actuation, electromagnetic actuation can provide larger displacement ranges at lower operating voltages, making it particularly attractive for centimetre-scale, polymer-based terahertz filters.
References:
[1] Martyniuk, M., et al., "Optical Microelectromechanical Systems Technologies for Spectrally Adaptive Sensing and Imaging". Adv. Funct. Mater., 2022
[2] Revuri, P.K., et al., "3D Printed Fabry-Pérot Filters for Terahertz Spectral Range". J Infrared, Millimeter,Terahertz Waves, 2022
| I am the presenting author | Yes |
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