Martes, 16 de Abril de 2019
Noticia en inglés
Finding terahertz (THz) light is extremely beneficial for two primary factors:
To start with, THz technology is ending up being an essential component in applications regarding security (such as airport scanners), cordless information communication, and quality assurance, to point out just a few. Nevertheless, existing THz detectors have shown strong limitations in regards to concurrently fulfilling the requirements for level of sensitivity, speed, spectral variety, having the ability to run at room temperature, etc.
Second Of All, it is a really safe type of radiation due to its low-energy photons, with more than a hundred times less energy than that of photons in the visible light range.
Lots of graphene-based applications are expected to emerge from its usage as material for identifying light. Graphene has the particularity of not having a bandgap, as compared to basic products used for photodetection, such as silicon. The bandgap in silicon triggers occurrence light with wavelengths longer than one micron to not be absorbed and hence not detected. In contrast, for graphene, even terahertz light with a wavelength of hundreds of microns can be taken in and spotted. Whereas THz detectors based on graphene have revealed appealing results so far, none of the detectors up until now might beat commercially readily available detectors in terms of speed and sensitivity.
In a recent study, ICFO scientists Sebastia?n Castilla and Dr. Bernat Terre?s, led by ICREA Prof. at ICFO Frank Koppens and previous ICFO scientist Dr. Klaas-Jan Tielrooij (now Junior Group Leader at ICN2), in partnership with researchers from CIC NanoGUNE, NEST (CNR), Nanjing University, Donostia International Physics Center, University of Ioannina and the National Institute for Material Sciences, have been able to conquer these obstacles. They have established an unique graphene-enabled photodetector that operates at room temperature, and is highly sensitive, extremely fast, has a wide dynamic variety and covers a broad range of THz frequencies.
< img alt ="[Img #55100]" src="https://noticiasdelaciencia.com/upload/images/04_2019/6435_198390 _ web.jpg" >
Left) Schematic representation of the main part of the graphene-based THz photodetector device, including the hBN-encapsulated graphene channel, on top of the narrow-gap antenna structure. By applying unique voltages to the left and ideal antenna branches, a pn-junction is created in the graphene channel with unequal Seebeck coefficients left wing and right of the junction. Incident light is focused by the antenna above the gap, which is where the photoresponse is produced. (Right) Measurement of a THz focus, gotten by scanning the THz detector in the plane of the focus. The observation of several rings of the Airy pattern show the high sensitivity of the detector. (Credit: ICFO)
In their experiment, the scientists were able to optimize the photoresponse mechanism of a THz photodetector utilizing the following approach. They incorporated a dipole antenna into the detector to focus the event THz light around the antenna gap region. By fabricating a very little (100 nm, about one thousand times smaller than the density of a hair) antenna space, they were able to get a fantastic intensity concentration of THz incident light in the photoactive area of the graphene channel. They observed that the light taken in by the graphene creates hot carriers at a pn-junction in graphene; consequently, the unequal Seebeck coefficients in the p- and n-regions produce a local voltage and a current through the gadget generating a huge photoresponse and, thus, causing an extremely high level of sensitivity, high speed reaction detector, with a broad vibrant variety and a broad spectral coverage.
The outcomes of this study open a path towards the development a totally digital low-cost video camera system. This might be as inexpensive as the electronic camera inside the smartphone, considering that such a detector has shown to have a very low power intake and is fully suitable with CMOS technology. (Fuente: ICFO-The Institute of Photonic Sciences)