Abstract-Hybrid 3-D Printing Technology for Tunable THz Applications

William J. Otter,  Stepan Lucyszyn,

http://ieeexplore.ieee.org/document/7797186/

In recent years, additive manufacturing has experienced rapid growth, due to its inherent capabilities for creating arbitrary 3-D structures, accessibility, and associated low manufacturing costs. This paper first reviews the state of the art in 3-D printing for terahertz (THz) applications and identifies the critical features required for such applications. The future potential for this technology is demonstrated experimentally with the first 3-D-printed, optically controlled THz IQ vector modulator. Here, miniature high-resistivity silicon implants are integrated into metal-pipe rectangular waveguides. The 3-D-printed split-block assembly also houses two packaged infrared laser diodes and a heat sink. The measured performance of a proof-of-principle 4-quaternary amplitude modulation (4-QAM) vector modulator that operates up to 500 GHz is reported. This new hybrid 3-D printing THz technology, which combines semiconductor devices with potentially low-cost, high-performance passive guided-wave structures represents a paradigm shift and may prove to be an ideal solution for implementing affordable transceivers in future ubiquitous THz applications.

Abstract-LED-Switchable High-Q Packaged THz Microbeam Resonators

Stephen M. Hanham,   Munir M. Ahmad,   Stepan Lucyszyn,   Norbert Klein,

http://ieeexplore.ieee.org/document/7833200/

This paper describes the design, fabrication, and experimental characterization of photonic crystal microbeam cavity resonators for the terahertz band implemented using suspended dielectric rectangular waveguide (DRW) in high-resistivity silicon. Electrical quality factors of up to 11 900, combined with small modal volumes of 0.28 and 0.077 mm3, are demonstrated for devices operating at 100 and 200 GHz, respectively. The devices are found to be extremely light-sensitive, opening up new opportunities for light-controlled switching devices at terahertz frequencies. It is shown that the quality factor of the resonator can be tuned and the resonance extinguished through photo-illumination with an infrared light-emitting diode (IR LED). Additionally, the questions of thermal tunability and thermal stability of the resonators are examined. The demonstrated resonators are inherently suited to integration with DRW and, by silicon bulk micromachining, represent an attractive approach for realizing microphotonic-integrated circuits for terahertz systems-on-a-substrate.

Abstract-Predicting Atmospheric Attenuation Under Pristine Conditions Between 0.1 and 100 THz

Jingye Sun,  Fangjing Hu,  Stepan Lucyszyn

Calculated color map of mean band transmittance against frequency and fractional bandwidth for horizontal path links at sea level, using predictions from LBLRTM at 296 K over a 1 km path length

http://ieeexplore.ieee.org/document/7736955/

This multidisciplinary paper reports on a research application-led study for predicting atmospheric attenuation, and tries to bridge the knowledge gap between applied engineering and atmospheric sciences. As a useful comparative baseline, this paper focuses specifically on atmospheric attenuation under pristine conditions, over the extended terahertz spectrum. Three well-known simulation software packages (`HITRAN on the Web', MODTRAN®4, and LBLRTM) are compared and contrasted. Techniques used for modeling atmospheric attenuation have been applied to investigate the resilience of (ultra-)wide fractional bandwidth applications to the effects of molecular absorption. Two extreme modeling scenarios are investigated: horizontal path links at sea level and Earth-space path links. It is shown by example that a basic software package (`HITRAN on the Web') can give good predictions with the former, whereas sophisticated simulation software (LBLRTM) is required for the latter. Finally, with molecular emission included, carrier-to-noise ratio fade margins can be calculated for the effects of line broadening due to changes in macroscopic atmospheric conditions with sub-1-THz ultra-narrow fractional bandwidth applications. Outdoors can be far from pristine, with additional atmospheric contributions only briefly introduced here; further discussion is beyond the scope of this paper, but relevant references have been cited.