Hexagonal boron nitride (hBN) is a two-dimensional van der Waals material and is composed of boron and nitrogen atoms in a hexagonal lattice. hBN is the wide-bandgap semiconductor with a band of 6.4 eV and shows efficient band edge cathodoluminescence at 215 nm as well as lasing behavior. Here I will present the efficient DUV electroluminescence (EL) in band edge emission at 215 nm as well as broad 303-333 nm emission peaks from hBN van der Waals heterostructure. We observed that 303-333 nm broad emissions with phonon replica of optical phonon energy of hBN based on the Franck-Condon principle, which are attributed to the electric field induced color centers and its highly localized excitons features. These results demonstrate the promising developments of a highly efficient solid-state DUV light source at the nanoscale and allow the development of the key architectures for DUV nanophotonic, bio-sensing, high-precision metrology, and quantum information.
Hexagonal boron nitride (hBN) is a two-dimensional van der Waals material and is composed of boron and nitrogen atoms in a hexagonal lattice. hBN is the wide-bandgap semiconductor with a band of 6.4 eV and shows the efficient band edge cathodoluminescence at 215 nm as well as lasing behavior. Here I will present the efficient DUV electroluminescence (EL) in band edge emission at 215 nm as well as broad 303-333 nm emission peaks from hBN van der Waals heterostructure. We observed that 303-333 nm broad emissions with phonon replica of optical phonon energy of hBN based on the Franck-Condon principle, which are attributed to the electric field induced color centers and its highly localized excitons features. I will also present the tunable DUV light emission around band edge emission of 215 nm as a function of electric field direction and discuss the possible origin of DUV EL from hBN van der Waals heterostructures.
The potential for establishing energy gaps by pseudo-magnetic fields in strain-engineered graphene has sparked much interest recently. However, the limited sizes of induced pseudo-magnetic fields and the complicated platforms for straining graphene have thus far prevented researchers from harnessing the unique pseudo-magnetic fields in optoelectronic devices. In this work, we present an experimental demonstration of triaxially strained suspended graphene structures capable of obtaining quasi-uniform pseudo-magnetic fields over a large scale. The novel metal electrode design functions as both stressors and current injectors. We also propose a hybrid laser structure employing a 2D photonic crystal and triaxially strained graphene as an optical cavity and gain medium, respectively.
The understanding of two-dimensional (2D) materials has grown tremendously, especially for isolated monolayers. Recently, complex structures formed by stacking 2D materials have attracted considerable attention. This is in part due to the fact that the properties of monolayers are known to be influenced by their surroundings. Consequently, monolayer properties are predicted to be affected by “heterostructuring”. A study involving high-charge-carrier-density effects and dynamics is presented here for monolayers of WSe2 on different substrates and heterostructures comprised of 2D h-BN and WSe2. The influence of h-BN as well as the bilayer stacking order on the spectral and dynamical properties of WSe2- monolayer emission is discussed for the low-density regime and evidenced for high-density effects such as exciton-exciton annihilation and the Mott transition.
Graphene has received much interest from optical communities largely owing to its photon-like linear energy band structure called Dirac cone. While majority of the recent research has dealt with plasmon and polariton of the two-dimensional material, a recently reported graphene light emitter could render a new dimension of applications, particularly in high-speed optical communication. Moreover chemical vapor deposition (CVD) growth technique for graphene is available today providing means for scalable high quality graphene.
The reported graphene emitter provides broadband light emission from visible to mid-infrared which could be instrumental in multi-color display units and optical communications, however a truly large scale implementation has not previously been achieved. Here we demonstrate a CMOS-compatible 262,144 light-emitting pixels array (10 x 10 mm2) based on suspended CVD graphene nano-electro-mechanical systems (GNEMS). A single photoemission area is 19.6 µm2 and a unit pixel is consisting of 512 photoemission devices (16 x 16) where a multiplexer and a digital to analog converter (DAC) are used to control each pixel. This work clearly demonstrates scalability of multi-channel GNEMS light-emitting array, an atomically thin electro-optical module, and further paves a path for its commercial implementation transparent display or high-speed optical communication.
Ultrafast electrically driven light emitter is a critical component in the development of the high bandwidth free-space and on-chip optical communications. Traditional semiconductor based light sources for integration to photonic platform have therefore been heavily studied over the past decades. However, there are still challenges such as absence of monolithic on-chip light sources with high bandwidth density, large-scale integration, low-cost, small foot print, and complementary metal-oxide-semiconductor (CMOS) technology compatibility. Here, we demonstrate the first electrically driven ultrafast graphene light emitter that operate up to 10 GHz bandwidth and broadband range (400 ~ 1600 nm), which are possible due to the strong coupling of charge carriers in graphene and surface optical phonons in hBN allow the ultrafast energy and heat transfer. In addition, incorporation of atomically thin hexagonal boron nitride (hBN) encapsulation layers enable the stable and practical high performance even under the ambient condition. Therefore, electrically driven ultrafast graphene light emitters paves the way towards the realization of ultrahigh bandwidth density photonic integrated circuits and efficient optical communications networks.
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