A repository & source of cutting edge news about emerging terahertz technology, it's commercialization & innovations in THz devices, quality & process control, medical diagnostics, security, astronomy, communications, applications in graphene, metamaterials, CMOS, compressive sensing, 3d printing, and the Internet of Nanothings. NOTHING POSTED IS INVESTMENT ADVICE! REPOSTED COPYRIGHT IS FOR EDUCATIONAL USE.
Showing posts with label Taylan Takan. Show all posts
Showing posts with label Taylan Takan. Show all posts
Tuesday, August 15, 2017
Abstract-Compressive Sensing Imaging at Sub-THz Frequency in Transmission Mode
Vedat Ali Özkan, Yıldız Menteşe, Taylan Takan, Asaf Behzat Şahin, Hakan Altan
https://link.springer.com/chapter/10.1007/978-94-024-1093-8_7
Due to lack of widespread array imaging techniques in the THz range, point detector applications coupled with spatial modulation schemes are being investigated using compressive sensing (CS) techniques. CS algorithms coupled with innovative spatial modulation schemes which allow the control of pixels on the image plane from which the light is focused onto single pixel THz detector has been shown to rapidly generate images of objects. Using a CS algorithm, the image of an object can be reconstructed rapidly. Using a multiplied Schottky diode based multiplied millimeter wave source working at 113 GHz, a metal cutout letter F, which served as the target was illuminated in transmission. The image is spatially discretized by laser machined, 10 × 10 pixel metal apertures to demonstrate the technique of spatial modulation coupled with compressive sensing. The image was reconstructed by modulating the source and measuring the transmitted flux through the metal apertures using a Golay cell. Experimental results were compared to reference image to assess reconstruction performance using χ2 index. It is shown that a satisfactory image is reconstructed below the Nyquist rate which demonstrates that after taking into account the light intensity distribution at the image plane, compressive sensing is an advantageous method to be employed for remote sensing with point detectors.
Monday, July 25, 2016
Abstract-Observation of Gate-Tunable Coherent Perfect Absorption of Terahertz Radiation in Graphene
Nurbek KakenovOsman BalciTaylan TakanVedat Ali OzkanHakan AltanCoskun Kocabas
https://figshare.com/articles/Observation_of_Gate-Tunable_Coherent_Perfect_Absorption_of_Terahertz_Radiation_in_Graphene/3497729
Abstract-We report experimental observation of electrically tunable coherent perfect absorption (CPA) of terahertz (THz) radiation in graphene. We develop a reflection-type tunable THz cavity formed by a large-area graphene layer, a metallic reflective electrode, and an electrolytic medium in between. Ionic gating in the THz cavity allows us to tune the Fermi energy of graphene up to 1 eV and to achieve a critical coupling condition at 2.8 THz with absorption of 99%. With the enhanced THz absorption, we were able to measure the Fermi energy dependence of the transport scattering time of highly doped graphene. Furthermore, we demonstrate flexible active THz surfaces that yield large modulation in the THz reflectivity with low insertion losses. We anticipate that the gate-tunable CPA will lead to efficient active THz optoelectronics applications.
https://figshare.com/articles/Observation_of_Gate-Tunable_Coherent_Perfect_Absorption_of_Terahertz_Radiation_in_Graphene/3497729
Abstract-We report experimental observation of electrically tunable coherent perfect absorption (CPA) of terahertz (THz) radiation in graphene. We develop a reflection-type tunable THz cavity formed by a large-area graphene layer, a metallic reflective electrode, and an electrolytic medium in between. Ionic gating in the THz cavity allows us to tune the Fermi energy of graphene up to 1 eV and to achieve a critical coupling condition at 2.8 THz with absorption of 99%. With the enhanced THz absorption, we were able to measure the Fermi energy dependence of the transport scattering time of highly doped graphene. Furthermore, we demonstrate flexible active THz surfaces that yield large modulation in the THz reflectivity with low insertion losses. We anticipate that the gate-tunable CPA will lead to efficient active THz optoelectronics applications.
Saturday, October 24, 2015
Abstract-Terahertz modulation using a bandpass filter combined with a graphene supercapacitor
Taylan Takan, Mehmet A. Nebioglu, Hakan Altan
Middle East Technical Univ. (Turkey)
Nurbek Kakenov, Osman Balci, Coskun Kocabas
Bilkent Univ. (Turkey)
Proc. SPIE 9651, Millimetre Wave and Terahertz Sensors and Technology VIII, 96510F (October 21, 2015); doi:10.1117/12.2195140
Graphene is proving to be an efficient medium for the control of mm-wave/THz radiation. Its electrical and dielectric properties allows it to be incorporated into various existing device architectures. One such application is in the modulation of the amplitude of the propagating THz radiation. Due to its electrical properties this interaction is typically broadband in nature. To make this frequency selective we propose the use of metamaterials or frequency selective surfaces. Generally, these structures perform the frequency filtering by modifying the propagation of the input wave with respect to changing structural parameters of the device itself. By fabricating a frequency selective surface based on a periodic circular hole array on an aluminum sheet we show that the transmission of a narrow band of THz radiation can be modulated when the sheet is combined with a highly efficient graphene based supercapacitor device. The modulation depth of the device was 15% in the frequency region of interest. The simple structure of the device coupled with the obtained performance shows that graphene based devices have great potential for the development of THz technologies.
© (2015) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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