High performance bilayer-graphene Terahertz detectors

We report bilayer-graphene field effect transistors operating as THz broadband photodetectors based on plasma-waves excitation. By employing wide-gate geometries or buried gate configurations, we achieve a responsivity $\sim 1.2V/W (1.3 mA/W)$ and a noise equivalent power $\sim 2\times 10^{-9} W/Hz^{-1/2}$ in the 0.29-0.38 THz range, in photovoltage and photocurrent mode. The potential of this technology for scalability to higher frequencies and the development of flexible devices makes our approach competitive for a future generation of THz detection systems.Comment: 8 pages, 5 figures. Submitted to Applied Physics Letter

Analysis of sodium copper chlorophyllin and sodium magnesium chlorophyllin by time-domain THz spectroscopy

The terahertz absorption spectra of sodium magnesium chlorophyllin (Chl-Mg-Na) and sodium copper chlorophyllin (Cu-Chl), two major members of the chlorophyll derivative family, have been measured in the range 0.2-2.5 THz, at room temperature. The capability of terahertz spectroscopy for quantitative characterization of Chl-Mg-Na intermolecular vibrations was investigated and the sensitivity of transitions with degree of hydration by changes in the molecular environment was examined. For the Cu-Chl derivative, a broad feature was observed around 1.8 THz which currently hinders clear Cu-Chl identification and quantification

Investigating the low-frequency vibrations of chlorophyll derivatives using terahertz spectroscopy

The terahertz absorption spectra of sodium magnesium chlorophyllin (Chl-Mg-Na) and sodium copper chlorophyllin (Cu-Chl), two major members of the chlorophyll derivative family, have been measured in the range 0.2-3.0 THz (6.6-100 cm-1), at room temperature. Additionally, surface-enhanced Raman scattering spectroscopy was used to supplement data in the higher frequency range. The capability of terahertz spectroscopy for quantitative characterization of Chl-Mg-Na intermolecular vibrations was investigated and the sensitivity of the 1.82-THz feature with degree of hydration by changes in the molecular environment was examined. For Cu-Chl derivative, a broad feature was observed around 1.8 THz which currently hinders clear Cu-Chl identification and quantification

Temperature-dependent low-frequency vibrational spectra of sodium magnesium chlorophyllin

Terahertz time-domain spectroscopy has been used to investigate the vibrational spectra of polycrystalline sodium magnesium chlorophyllin - one of the natural derivatives of chlorophyll - over the temperature range 88 K–298 K. A number of well-resolved absorption peaks were observed in the frequency range 0.2–2.5 THz, which are interpreted as originating from mixed character of intramolecular and intermolecular vibration modes. As the temperature is increased, the observed absorption features resolve into broader peaks. The peak centered at 1.83 THz shifts towards higher frequencies, indicating that for this feature, significant intermolecular anharmonicity exist

Field Effect Transistors for Terahertz Detection: Physics and First Imaging Applications

Resonant frequencies of the two-dimensional plasma in FETs increase with the reduction of the channel dimensions and can reach the THz range for sub-micron gate lengths. Nonlinear properties of the electron plasma in the transistor channel can be used for the detection and mixing of THz frequencies. At cryogenic temperatures resonant and gate voltage tunable detection related to plasma waves resonances, is observed. At room temperature, when plasma oscillations are overdamped, the FET can operate as an efficient broadband THz detector. We present the main theoretical and experimental results on THz detection by FETs in the context of their possible application for THz imaging.Comment: 22 pages, 12 figures, review pape

Terahertz imaging using graphene field-effect-transistors

International audienceInterest in terahertz (THz) systems and technology has grown significantly over the past 10 years for their potential in non-invasive imaging, sensing and high-data-rate wireless communication. Waves at THz frequencies present an alternative to x-rays for imaging through paper, cloth, wood, concrete, plastic and many other materials. In contrast to x-rays they are non-ionizing and therefore inherently safe. Applications of THz radiations range from nondestructive testing to medical imaging, security screening of objects and persons. Several groups have also considered using THz waves to transmit data in wireless communications. Wireless THz communications for which THz waves are the free-space carrier of data are recognized as the promising breakthrough solution to achieve data-rates up to 100 Gbps. THz imaging and wireless communication applications suffer, however, from the lack of fast and low-cost detectors operating at room temperature and in this work we show that graphene based plasma nanotransistors can be a good alternative. .Nanotransistors offer great prospect for the development of innovative THz detectors. The interest in using field-effect transistors for THz applications was initiated by the theoretical work of Dyakonov and Shur, who predicted that the nonlinear properties of the 2D plasma in the transistor channel can be used for detection of THz waves at frequencies significantly higher than the transistor cut-off frequency. Graphene field-effect nanotransistors were recently demonstrated showing maturity of graphene microelectronics. In this paper, we present extensive studies on first THz detectors based on monolayer and bilayer graphene field effect transistors. The specific detection sign reversal related to the graphene Dirac point change of electron to hole conductivity is clearly demonstrated. We show that the detectors consisting of a gated 2D massless fermion gas as rectifying element and an integrated coupling antenna achieve a responsivity above 1.2 V/W (1.3 mA/W) in photovoltage and photocurrent mode respectively, and a noise equivalent power below 2 10-9 W/Hz0.5 We show also that these detectors can operating as sensitive room-temperature broadband THz detectors in THz imaging systems. Feasibility of THz food industry quality control and agriculture watering control imagers using graphene nanotransitor sensors/detectors is demonstrated

Exaltation de la génération de second harmonique dans les cristaux photoniques à base de nitrures

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