This project is aimed to develop and implement a new type of terahertz modulator by exploiting, for the first time, MEMS reconfigurable subwavelength metallic slits. This terahertz modulator takes advantage of low loss and broadband transmission of electromagnetic waves through multiple layers of subwavelength metallic slits to offer unprecedented modulation bandwidths of at least ten times higher than the prior art. Moreover, this terahertz modulator offers up to 100 percent modulation index while operating at competitive modulation speeds and modulation voltages compared to the state-of-the art. While theoretical investigations provide a deep understanding of electromagnetic wave interaction with multi-layered subwavelength metallic slits, the experimental effort provides an intuitive insight to develop proper designs and fabrication processes for realizing a fully integrated terahertz modulator. Various geometries will be explored to mitigate the tradeoff between the modulation voltage, modulation bandwidth, modulation index, modulation speed, and modulator reliability.
The outcome of this research will enable terahertz spatial beam forming and developing high-performance active and passive terahertz imaging systems based on compressive sensing. The integrated education activities will train graduate and undergraduate students on interdisciplinary research.
In spite of their great promise, one of the major limitations of existing terahertz systems is the lack of high-performance terahertz modulators. We have found a better way to build terahertz modulators that could improve performance of terahertz imaging, sensing and communication systems. The developed terahertz modulators offer significantly higher modulation depths and modulation bandwidth compared to the state of the art. This enables higher sensitivity terahertz imaging, sensing and communication systems. In order to realize a terahertz modulator with high modulation depth and modulation bandwidth, we have optimized a type of MEMS-reconfigurable double-layered mesh filter that can be reconfigured from a capacitive filter to an inductive filter with a relatively small geometrical change. This enables device reconfiguration from a low-pass filter to a high-pass filter and, thus, significant intensity modulation. The unique advantage of this modulation technique compared with the previously demonstrated terahertz modulation schemes is reconfiguring the device geometry, which enables radical changes in the device scattering parameters over a broad range of frequencies. The presented terahertz modulation scheme is just the beginning of the exciting demonstrations of the great promise of MEMS-reconfigurable mesh filters for terahertz radiation manipulation, in general, and terahertz intensity modulation, specifically. The design can be modified in the future to offer higher modulation depths, broader operation bandwidths, and faster modulation speeds by adapting miniature MEMS switches with mechanical architectures optimized for reliable operation at high actuation speeds. Additionally, mesh filter configuration can be modified to realize high-performance terahertz phase modulators, tunable filters, and beam-steering devices through the presented MEMS-reconfigurable mesh filters. Moreover, alternative MEMS switch configurations can be employed to extend device operation to mid-infrared frequency ranges, where low-loss and efficient modulators are in great demand to realize point-to-point communication systems at atmospheric transparent windows.
