Terahertz/ mmWave Systems
Objective: To develop a suite of devices (modulators, absorbers, imagers etc.) that can operate in the terahertz region of the electromagnetic spectrum.
Approach: Our approach to fill the terahertz-gap is based on the active control of a unique class of artificial materials, namely “metamaterials” using plasma wave behavior of gated two-dimensional electron gas in the channel of GaAs HEMT or nanometer scale CMOS transistors. A key benefit of this approach is that the operation is not limited by the fT of the underlying transistor in the technology. The fundamental approach uniquely combines the emerging field of electromagnetic metamaterials with novel plasma wave electronic transport phenomena in transistors. This allowed us to demonstrate the first of its kind terahertz quasi-optical THz modulator with record modulation depth (33%) and record data rate (10 MHz) of its time in a commercial 0.25um GaAs HEMT process. We repurposed this modulator to implement an all solid-state THz spatial light modulator in a commercial GaAs process for the first time. THz SLM was used to demonstrate multi-level THz communication, or to implement single pixel THz imaging of occlusive object. In another project, we have designed perfect absorbers at single, dual and multiple bands in the microwave and terahertz spectrum using metamaterials on flexible (parylene, polyimide) or hard (microwave circuit boards) substrates. We have also embedded non-foster circuits within metamaterials to enable novel functions such as compensating the losses in metamaterials or broaden their bandwidth. And finally, we demonstrated a truly monolithic compact low power low voltage THz modulator using slot waveguide in a GaAs process with record performance of its time.
Sample publications:
Approach: Our approach to fill the terahertz-gap is based on the active control of a unique class of artificial materials, namely “metamaterials” using plasma wave behavior of gated two-dimensional electron gas in the channel of GaAs HEMT or nanometer scale CMOS transistors. A key benefit of this approach is that the operation is not limited by the fT of the underlying transistor in the technology. The fundamental approach uniquely combines the emerging field of electromagnetic metamaterials with novel plasma wave electronic transport phenomena in transistors. This allowed us to demonstrate the first of its kind terahertz quasi-optical THz modulator with record modulation depth (33%) and record data rate (10 MHz) of its time in a commercial 0.25um GaAs HEMT process. We repurposed this modulator to implement an all solid-state THz spatial light modulator in a commercial GaAs process for the first time. THz SLM was used to demonstrate multi-level THz communication, or to implement single pixel THz imaging of occlusive object. In another project, we have designed perfect absorbers at single, dual and multiple bands in the microwave and terahertz spectrum using metamaterials on flexible (parylene, polyimide) or hard (microwave circuit boards) substrates. We have also embedded non-foster circuits within metamaterials to enable novel functions such as compensating the losses in metamaterials or broaden their bandwidth. And finally, we demonstrated a truly monolithic compact low power low voltage THz modulator using slot waveguide in a GaAs process with record performance of its time.
Sample publications:
- High speed terahertz modulation from metamaterials with embedded high electron mobility transistors, Optics Express, vol. 19 Issue 10, pp.9968-9975, 2011.
- Single and dual band 77/95/110 GHz metamaterial absorbers on flexible polyimide substrates, Applied Physics Letters, 99, 264101, 2011.
- High-speed terahertz modulator based on tunable terahertz slot waveguide, Nature Scientific Reports, 7, 40933, 2017.
- Experimental realization of metamaterial detector focal plane array, Physical Review Letters, 2012, Vol. 109, Issue 17, 177401, 2012
- A low-voltage high-speed terahertz spatial light modulator using active metamaterial." APL Photonics 1, 8 pp: 086102, 2016.
- Wireless multi-level terahertz amplitude modulator using active metamaterial-based spatial light modulation, Optics Express 24.13 14618-14631, 2016.
- Loss compensation in metamaterials through embedding of active transistor based negative differential resistance circuits, Optics Express, Vol. 20 Issue 20, pp.22406-22411, 2012
- Microwave diode switchable metamaterial reflector/absorber, Applied Physics Letters, 103 (3), 031902-4, July 2013.