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We study the broadband optical conductivity and ultrafast carrier dynamics of epitaxial graphene in the few-layer limit. Equilibrium spectra of nominally buffer, monolayer, and multilayer graphene exhibit significant terahertz and…
We present a graphene photodetector for telecom applications based on a silicon photonic crystal defect waveguide. The photonic structure is used to confine the propagating light in a narrow region in the graphene layer to enhance…
X-ray photoelectron spectroscopy of graphene is important both for its characterization and as a model for other carbon materials. Despite great recent interest, the intrinsic photoemission of its single layer has not been unambiguously…
The combination of plasmonic nanoparticles and graphene enhances the responsivity and spectral selectivity of graphene-based photodetectors. However, the small area of the metal-graphene junction, where the induced electron-hole pairs…
We study the interaction of graphene with ultrashort few femtosecond long optical pulse. For such a short pulse, the electron dynamics is coherent and is described within the tight-binding model of graphene. The interaction of optical pulse…
The equilibrium optical phonons of graphene are well characterized in terms of anharmonicity and electron-phonon interactions, however their non-equilibrium properties in the presence of hot charge carriers are still not fully explored.…
The optical properties of graphene are made unique by the linear band structure and the vanishing density of states at the Dirac point. It has been proposed that even in the absence of a semiconducting bandgap, a relaxation bottleneck at…
Using ultrafast optical pump-probe spectroscopy, we have measured carrier relaxation times in epitaxial graphene layers grown on SiC wafers. We find two distinct time scales associated with the relaxation of nonequilibrium photogenerated…
Ultrafast optical pump-probe spectroscopy measurement on monolayer graphene observes significant optical nonlinearities. We show that strongly photoexcited graphene monolayers with 35 fs pulses quasi-instantaneously build up a broadband,…
The ability to manipulate electrons with the intense laser pulse enables an unprecedented control over the electronic motion on its intrinsic timescale. Present work explores the desired control of photocurrent generation in monolayer…
We study the carrier dynamics in epitaxially grown graphene in the range of photon energies from 10 - 250 meV. The experiments complemented by microscopic modeling reveal that the carrier relaxation is significantly slowed down as the…
We report on the efficient photodetection (PD) properties of graphene based p-i-n photodetector, where all the three layers are either single or multilayer graphene sheets. We report the bandwidth and responsivity performance of the device.…
While the Dirac band structure of graphene has established it as a leading platform for ultrafast optoelectronics, its non-perturbative nonlinear response under intense excitation remains poorly understood. Here, we report ultrafast…
Understanding the ultrafast dynamics of photoexcited charges in graphene is essential, as the microscopic mechanisms underlying these dynamics determine many of graphene's optical, optothermal, and optoelectronic properties. These are…
Graphene is an ideal material for hot-electron bolometers, due to its low heat capacity and weak electron-phonon coupling. Nanostructuring graphene with quantum dot constrictions yields detectors with extraordinarily high intrinsic…
We report on the observation of terahertz radiation induced edge photogalvanic currents in graphene, which are nonlinear in intensity. The increase of the radiation intensities up to MW/cm$^2$ results in a complex nonlinear intensity…
Graphene has emerged as a promising material for photonic applications fuelled by its superior electronic and optical properties. However, the photoresponsivity is limited by the low absorption cross section and ultrafast recombination…
Light incident upon materials can induce changes in their electrical conductivity, a phenomenon referred to as photoresistance. In semiconductors, the photoresistance is negative, as light-induced promotion of electrons across the band gap…
We propose and evaluate the graphene layer (GL) infrared photodetectors (GLIPs) based on the van der Waals (vdW) heterostructures with the radiation absorbing GLs. The operation of the GLIPs is associated with the electron photoexcitation…
The integration of optoelectronic devices, such as transistors and photodetectors (PDs), into wearables and textiles is of great interest for applications such as healthcare and physiological monitoring. These require flexible/wearable…