Abstract-Enhancement of terahertz absorption in graphene monolayer with Bragg grating and metallic film

Jun Wu

https://www.spiedigitallibrary.org/journals/Journal-of-Nanophotonics/volume-13/issue-4/046002/Enhancement-of-terahertz-absorption-in-graphene-monolayer-with-Bragg-grating/10.1117/1.JNP.13.4.046002.short?SSO=1

The absorption enhancement in the graphene monolayer for the terahertz frequency is investigated. This is achieved by placing the graphene monolayer on a dielectric grating backed with a reduced Bragg grating and a metallic mirror. Complete absorption is achieved at resonance and the absorption spectra exhibit an ultranarrow shape, which is attributed to the combined effects of the guided mode resonance with dielectric grating and the photonic bandgap with Bragg grating. Moreover, the designed graphene absorber possesses antenna-like response and thus can be used as a thermal emitter with high directionality. To disclose the physical origins of such absorption effects, the electric-field intensity distributions are investigated. Furthermore, the peak position of the absorption spectra can be tuned by only a change in the Fermi level. Our results may potentially be used for developing the next-generation graphene-based optoelectronic devices.

© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE) 1934-2608/2019/$28.00 © 2019 SPIE

Abstract-Analog signal processing in the terahertz communication links using waveguide Bragg gratings: example of dispersion compensation

Tian Ma, Kathirvel Nallapan, Hichem Guerboukha, and Maksim Skorobogatiy

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-10-11009

We study the possibility of analog signal processing for the upcoming terahertz (THz) high-bitrate communications using as an example the problem of dispersion compensation in the THz communication links. In particular, two Waveguide Bragg Grating devices (WBGs) operating in the transmission mode are detailed. WBGs are designed by introducing periodic corrugation onto the inner surface of the metalized tubes. The resultant devices operate in a single mode regime either in the vicinity of the modal cutoff or in the vicinity of a bandgap edge, featuring large negative group velocity dispersions (GVD). We fabricate the proposed WBGs using 3D stereolithography, and metallize them using wet chemistry. Optical properties of the fabricated WBGs are investigated both theoretically and experimentally. The results confirm single mode guidance, relatively high coupling efficiency, as well as large negative group velocity dispersions in the range of several -100’s ps/(THz · cm) in the vicinity of 0.14THz. This makes the short sections of proposed WBGs suitable for compensating positive dispersion incurred in the THz wireless links or fiber-assisted THz interconnects for signals of several-GHz bandwidth. Finally, we comment on the challenges associated with the analog signal processing in the THz spectral range.

© 2017 Optical Society of America

Abstract-Apodization of terahertz Bragg gratings in subwavelength polymer fiber

Shu Fan Zhou, Laurence Reekie, Hau Ping Chan, Kwai Man Luk, and Yuk Tak Chow  »View Author Affiliations

http://www.opticsinfobase.org/ol/abstract.cfm?uri=ol-38-15-2807

We report on an apodization scheme for terahertz fiber Bragg gratings. The grating consists of only 90 ablated notches on two opposite sides of a subwavelength polymer fiber. The grating strength can be effectively tuned by controlling the longitudinal shift between the two-sided notches, and apodization can be achieved by applying an envelope profile. Side lobe suppression of 14 dB was experimentally observed when compared with an unapodized grating.

© 2013 Optical Society of America