Abstract and Review-Review of photomixing continuous-wave terahertz systems and current application trends in terahertz domain

Reza Safian, Galia Ghazi,  Nafiseh Mohammadian,

Main THz detectors are thermal detectors, electro-optical detectors, and PCAs.

https://www.spiedigitallibrary.org/journals/Optical-Engineering/volume-58/issue-11/110901/Review-of-photomixing-continuous-wave-terahertz-systems-and-current-application/10.1117/1.OE.58.11.110901.full?SSO=1

Within the last two decades, terahertz systems have become a well-established tool in scientific laboratories and industrial research and development departments. Unlike the methods of pulsed terahertz radiation that mainly rely on ultrafast optical technology, the technology behind continuous-wave terahertz sources and detectors has a long history involving many different types of technical schemes. The intent is to provide a brief review of the continuous-wave terahertz systems that are based on photomixing and current application trends in the field of terahertz technology

Abstract-Graphene Based Double Ring Label-Free Terahertz Sensor with High Sensitivity

Fatemeh Ghaedi Vanani, Alireza Fardoost, and Reza Safian

https://www.osapublishing.org/abstract.cfm?uri=ES-2019-ETu3A.3

In our proposed structure, deformation of the normal double waveguide mode into photonic-plasmonic confined super mode by curving the waveguide into a small ring is exploited to increase the sensitivity of the terahertz label-free sensor.

© 2019 The Author(s)

Abstract-Towards subterahertz bandwidth ultracompact lithium niobate electrooptic modulators

Amirmahdi Honardoost, Farzaneh Arab Juneghani, Reza Safian, and Sasan Fathpour

Fig. 1 (a) 3-D schematic of the thin-film LN MZ EOMs; (b) Cross-section of the EOMs in the lateral y-z plane. The zoomed section shows the misalignment (ΔD = D2 – D1) of the rib’s center (D1) from the middle of the gap between the electrodes (D2).

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-5-6495

Achieving ultrahigh-speed electro-optic modulators (subterahertz modulation bandwidths) is shown to be feasible in the thin-film lithium niobate integrated photonic platform. Design guidelines for optimization of the main radio-frequency and optical parameters are presented, and 3-dB modulation bandwidth up to 400 GHz is proved attainable in 3-mm-long devices. Such unprecedented bandwidths pave the path towards utilizing the devices in advanced optical communication systems.

© 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Limiting factors for optical switching using nano-structured graphene-based field effect transistors

Ramin Emadi, Zaker Hossein Firouzeh, Reza Safian,  Abolghasem Zeidaabadi Nezhad

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-58-3-571

Thanks to the particular band diagram of graphene, it is recognized as a promising material for developing optoelectronic devices at the nano-scale. In this paper, a functional stack comprised of graphene and other materials is numerically investigated to extract the related capacitance-voltage curve by taking into account practical considerations regarding the nano-structured electronic devices. Polycrystalline silicon gates are used as electrical contacts in this stack, which are considered as semiconductor materials rather than metal contacts owing to the nano-scale dimensions of the constitutive materials. Moreover, graphene is effectively modeled to highlight its presence in the stack. Then, the stack is developed for the construction of a graphene field effect transistor (GFET) in order to examine the speed response of the stack. In this regard, by selecting the carrier mobility of 1500  cm2/(V·s)$\mathrm{}{}^{\mathrm{}}\mathrm{}\mathrm{}$ for graphene and a particular bias condition, the small-signal current gain of the GFET is computed so that according to the simulation results, the intrinsic cutoff frequency of 13.89 GHz is achieved.

© 2019 Optical Society of America