Spoof Surface Plasmon Polariton Based THz Circuitry

Terahertz, abbreviated as THz, is defined as the frequency band spanning from 300 GHz to 10 THz, which is located between the microwave from the electronic side of the electromagnetic (EM) spectrum to mid-Infra-Red on the photonic side of the EM spectrum. As accelerated research and innovations over the past seven decades have resulted in widespread commercialization of both electronic and photonic components, THz band has remained underdeveloped, underexploited, and mostly unallocated by the Federal Communications Commission (FCC). Though certain definitive merits of EM waves at THz have evoked interests of physicists, chemists, biologists and material scientists to deploy THz in Time-Domain Spectroscopy (TDS), bio-sensing, and classical imaging applications, the field of THz circuits (also known as THz electronics) has continued to remain in embryonic stage due to the speed limitations of conventional Silicon and compound semiconductor devices like Field Effect Transistors (FETs), Hetero-junction Bipolar Transistors (HBTs), and Hot Electron Mobility Transistors (HEMTs). On the other hand, conventional photonic devices cannot be readily adopted to design new THz circuits and systems. Our research vision in THz circuits and systems is to study the meta-material properties of THz in various forms of sub-wavelength structures and exploit those unique properties to invent the designs of large THz systems like the THz switch, Analog-to-Digital Converter (ADC), etc. The potential large bandwidth and high propagation speed helps photonic circuitry to be proposed against the above-mentioned challenges faced by its electronic counterpart. Optical-assisted as well as all-optical systems in various forms have been reported to realize different data-processing functionalities. For example, analog-to-digital converters (ADC) with the potential of high speed operation have been demonstrated by optical-assisted or all-optical approaches. Photonic logic has also been reported in numerous works by coding the Boolean information in the amplitude, phase or wavelength of the optical signals. Despite these efforts, however, the key element to address the fundamental deficiencies of CMOS circuit remained missing. The use of optical frequencies in these works brought about common shortcomings including dimension mismatch, lack of coherent detection, inflexibility, susceptibility to mechanical and environmental variations, and the presence of bulky optical elements (i.e., mirrors, beam splitters, lenses, etc.). More seriously, these works inherited sequential circuit designs directly from CMOS. It indicates that the cumulative delay still dominated the speed performance, which prevented further decrease of the circuit latency. In light of these problems, we foresee the implementation of THz circuitry as the next reasonable step to take in designing high-speed analog as well as digital circuits. Spoofed Surface Plasmon Polariton (SSPP) is known as a pseudo-surface mode in THz frequencies that mimics the slow wave nature and localized E-M field distribution of the plasmon mode typically observed in optical domain. By introducing periodic corrugations on the surfaces of a metal-dielectric-metal structure, SSPP mode is realized for propagating THz signal, and its mode dispersion is strongly dependent on the geometric dimensions as well as the material properties of the architecture. Recently propagation of THz wave utilizing Spoof surface plasmon polariton (SSPP) earned a great deal of attention due to the ability of SSPP modes to guide THz waves at very low dispersion. In this research, we exploit and investigate the SSPP modes in different periodic structure and utilizing them in different structure to introduce new THz devices, such as, polarization rotator, THz switch, ADC, etc.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/144105/1/mahdia_1.pd

Flexible terahertz wire grid polarizer with high extinction ratio and low loss

An aluminum-based THz wire grid polarizer is theoretically investigated and experimentally demonstrated on a sub-wavelength thin flexible and conformal foil of the cyclo-olefin Zeonor© polymer. THz time-domain spectroscopy characterization, performed on both flat and curved configurations, reveals a high extinction ratio between 40 and 45 dB in the 0.3-1 THz range and in excess of 30 dB up to 2.5 THz. The insertion losses are lower than 1 dB and are almost exclusively due to moderate Fabry-Perót reflections, which vanish at targeted frequencies. The polarizer can be easily fabricated with low-cost techniques such as roll-to-roll and/or large area electronics processes and promises to pen the way for a new class of flexible and conformal THz devices