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Two-dimensional van der Waals materials are two-dimensional crystals with strong covalent in-plane bonds and weak van der Waals interaction between the layers with a variety of different electronic, optical and mechanical properties. A very prominent class of two-dimensional materials are transition metal dichalcogenides and amongst them particularly the semiconducting subclass. Their properties include...
Remarkable advances in cooling and manipulating atomic gases have opened up new avenues to explore fundamental concepts in quantum many-body physics. Synthetically created potentials and control of atom-atom interactions have made it possible to tailor the properties of experimental systems at a microscopic level. This led to the concept of quantum simulation — here a system capable of reproducing...
The remarkably-high intrinsic optical nonlinearity of graphene can be pushed even further when the optical frequency is tuned to plasmon resonances hosted by the material when it is doped [1-4]. Atomistic simulations provide an accurate description of these phenomena, although their computational cost is prohibitive for large graphene nanostructures [3, 4]. An alternative formalism consists in relying...
Graphene plasmonics is a promising building block for high speed communication devices that takes advantage of strong confinement of the electromagnetic energy at sub-wavelength scales, tunable via charge carrier density through a gate voltage.[1] The fabrication of integrated optoelectronic devices based on graphene plasmons however is extremely challenging, and launching and conveying graphene plasmons...
Traditional lasers are composed by three basic elements: an amplifying medium, an external pumping setup, and an optical cavity that confines and shapes the emitted light in well-determined modes and directions. However, several modern approaches are extending this traditional laser paradigm into new avenues. Cavity-free stimulated emission of radiation has been widely studied in random lasers (RLs)...
Ultra-strong light-matter interactions can be realized in various physical systems and has thus attracted many experimental and theoretical investigations [1-4]. One possible realization is to couple strongly subwavelength split ring resonators (SRR) to the Landau level transition of a two dimensional electron (or hole) gas [2, 3]. In a previous work on parabolic AlGaAs/GaAs QWs, we showed that very...
The continuous development of terahertz (THz) sources has opened up many potential applications in spectroscopy, imaging and communications. One popular THz source is the quantum cascade laser (QCL), which has many desirable properties including compactness and high output power with a narrow emission frequency. For such a source to be successfully integrated into a THz communication system, it is...
Saturable absorption (SA) is an inherent property of photonic materials that manifests itself as an absorption quenching at high light intensities and is a key element for passive mode-locking (PML) in laser cavities, where continuous waves break into a train of ultrashort optical pulses. Currently, state-of-the-art semiconductor-based SA mirrors are routinely employed for PML lasers. However, these...
Electron-phonon scattering and anharmonicity are the dominant mechanisms, that enable to describe the equilibrium phonon properties in graphene [1] and Raman scattering is the main tool for their characterization [2]. In the first tens fs after the photoexcitation, an out of equilibrium distribution of (hot) electron is induced with respect to the (cold) phonon bath. Within a few picoseconds, the...
In twisted bilayer graphene (tBLG), the electronic and optical properties show interesting dependence on the interlayer rotation angle(0) with promising device applications [1,2]. The presence of the van Hove singularities in the density of states leads to an enhancement of the optical absorption at energies that depends on the rotation angle [2]. In single layer graphene, it has been shown that after...
We demonstrate that THz radiation can be transduced into acoustic waves in three-dimensional graphene (3D) sponge material through a photo thermal-acoustic (PTA) mechanism. The presented photo-acoustic converter has the unique ability to turn efficiently electromagnetic waves into heat and sound. The unique combination of thermal, mechanical and electronic properties of graphene sheets arranged in...
Active modulation of light with large optical bandwidths (∼100 nm [1]) is required in photonic devices, such as modulators for fiber communications [1] and saturable absorbers for ultrafast pulse generation [2,3]. Present modulators use expensive materials, (e.g. LiNbO3 [4], III-V semiconductors [5], and Ge on silicon-on-insulator (SOI) [6]), and are limited by narrowband operation (∼20 nm for quantum-confined...
Integrating single-photon sources into on-chip optical circuits is a challenge for scalable quantum-photonic technologies. Despite a plethora of single-photon sources reported to-date, all-electrical operation has been reported for only a few. The attractiveness of singlephoton sources in layered materials stems from their ability to operate at the fundamental limit of single-layer thickness, foreseeing...
Monolayer transition-metal dichalcogenides (TMDs) have recently emerged as fascinating novel materials. Like graphene, they can easily be exfoliated from bulk crystals. Unlike graphene, they have a large and direct band gap, making them attractive for potential applications in electronics or optoelectronics. They may also allow for novel device functionalities, as the spin and valley pseudospin degrees...
Solid state nanomechanical systems have received increased interest in applied and fundamental science in the past fifteen years. The combination of a very low mass and physical robustness has enabled measuring and demonstrating a variety of physical phenomena to an unprecedented level of accuracy, such as quantum behaviour at the macroscopic scale [1] and single interaction [2]. In particular, low...
Single layer graphene (SLG) has remarkable physical properties, with potential interest in the fields of electronics and photonics. While being single-atom thick, SLG presents a rather strong optical response, as a large optical absorption, resonance for all excitation frequencies up to the vacuum UV and, therefore, a strong broadband linear response, etc. It has been also pointed out that the non-linear...
One-dimensional (1D) graphene nanoribbons (GNRs) are promising materials for future electronics and optoelectronics. Their versatility in electronic properties makes it possible to use them as an active element in devices with a tunable band gap. Different from graphene, armchair-edge GNRs (AGNRs) are semiconducting with a direct bandgap [1-3]. However, until now their photophysical characterization...
Transition metal dichalcogenides (TMDs) are anisotropic materials crystallizing in a graphite-like structure, with each layer consisting of an hexagonal plane of transition metal atoms sandwiched between two hexagonal planes of chalcogen atoms. The weak interlayer Van der Waals bonds can be broken to isolate stable two-dimensional (2D) crystals. A wide variety of techniques have been developed to...
We report ultrafast pump-probe measurements on a graphene/MoS2 heterostructure and demonstrate sub picosecond exciton dissociation and charge transfer from MoS2 to graphene, one order of magnitude faster than in type II two-dimensional heterostructures [1]. The process can be controlled by applying an external gate and shifting the Fermi level of graphene. For pump-probe measurements we excite the...
Nanocomposites formed by graphene and metal nanoparticles (MNPs) are considered to become one of the most important technological advances due to their wide application range, as it is possible to exploit the combination of electronic characteristics in graphene and optical characteristics in metallic nanostructures [1]. Conventionally, the in-situ synthesis of these kind of nanocomposites is achieved...
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