Abstract-Flexible materials for terahertz optics: advantages of graphite-based structures

Rusnė Ivaškevičiūtė-Povilauskienė, Linas Minkevičius, Domas Jokubauskis, Andrzej Urbanowicz, Simonas Indrišiūnas, and Gintaras Valušis

 THz-TDS transmittance spectra and insets depict THz-CW two-dimensional THz beam profiles focused with a) metal TZP; b) graphite foil TZP; c) graphite on paper TZP; d) pure paper TZP. The beam cross sections at the maximum intensity are presented in a linear scale as a solid black line for each case. Maximum signal amplitude of the TZPs is normalized to the maximum amplitude of the unfocused beam.

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-9-11-4438

Flexible materials for applications in terahertz (THz) range imaging systems are investigated in this study. THz time-domain spectroscopy and THz imaging at 0.6 THz frequency are used to analyze optical properties of zone plates (TZP) with integrated cross-shaped filters, which are fabricated using direct laser writing on thin graphite, HB pencil-shaded graphite on paper, as well as reference metal-based and pure paper zone plates. Spectral features and focusing power comparable to the best metal-based TZP is achieved with graphite-based TZP. The pure paper and paper with pencil-shaded graphite TZPs showed increase in focusing power by a factor of ∼1.5, supporting numerical 3D finite-difference time-domain simulations. The findings show that graphite-based TZPs can serve as a flexible, compact, and inexpensive optics elements for emerging THz imaging systems.

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

Abstract-Compact solutions for spectroscopic solid-state-based terahertz imaging systems

Rimvydas Venckevičius,  Linas Minkevičius,  Antanas Reklaitis, Vincas Tamošiūnas,  Irmantas Kašalyns,  Domas Jokubauskis,  Dalius Seliuta,  Bogdan Voisiat,  Gediminas Račiukaitis,  Gintaras Valušis,

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10383/103830S/Compact-solutions-for-spectroscopic-solid-state-based-terahertz-imaging-systems/10.1117/12.2273353.short

Convenience in use of room-temperature terahertz (THz) imaging systems, reduction of their dimensions and presence of on-chip solutions remains one of prime interests for direct implementation aims. Solid-state-based solutions in miniaturization of spectroscopic THz imaging systems including novel semiconductor nanostructures bias-free emitters, diffractive THz optics components and their on-chip integration with THz detectors are discussed. In particular, pulsed optoelectronic terahertz emitter based on a δ-doped p-i-n-i GaAs/AlxGa1−xAs heterostructure was studied and it is demonstrated that the heterostructure can serve as efficient antenna- and bias-free surface emitter. Diffractive optics elements – Fresnel zone plates –with integrated band-pass filters were simulated employing Finite-difference time domain method. Structures were fabricated using the laser direct writing and investigated using electronic THz sources and an optically pumped terahertz laser. Advantages of on-chip integration of diffractive optics and bow-tie-shaped InGaAs-based terahertz detectors are revealed via detection enhancement. Bow-tie diodes properties in frequency scale and detection sensitivity are considered and compared for different materials. Homodyne detection and imaging of low-absorbing objects at 0.6 THz are demonstrated and discussed.

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