In‐Plane Field‐Driven Excitonic Electro‐Optic Modulation in Monolayer Semiconductor

Abstract

excitons [3,4] and their complexes [5][6][7] and hybrid quasi-particles such as cavity polariton and plexciton at room temperature. [8,9] These van der Waals semiconductors display various exciton-mediated electrooptic phenomena that are not seen in conventional semiconductors. Along with their ease of integration onto a photonic integrated circuit platform, [10][11][12][13] they hold great potential for on-chip electro-optic modulators. [14] The charge modulation of the optical response of 2D TMDs has been most widely studied in the static limit, proving useful for revealing their rich many-body physics. Exciton energy and oscillator strength are altered by various effects such as transfer of oscillator strength, [15] Pauli blocking, [16] binding energy reduction, [17] and renormalization of quasiparticle band gap. [18,19] The modulation of optical response in exciton energy is particularly pronounced in high quality samples. For example, it has been shown that the reflectance of a monolayer of MoSe 2 encapsulated by hexagonal boron nitride (hBN) can be electrostatically tuned by as much as 87%. [20][21][22][23][24] 2D semiconductors are attractive candidates for on-chip electro-optic modulators due to their ease of integration and rich exciton-mediated phenomena. While electrostatic doping and out-of-plane field effect have been extensively studied, in-plane field-induced phenomena remain largely unexplored. Here electro-optic response of monolayer WSe 2 subject to modulating in-plane electric fields probed by electroabsorption and electroreflectance spectroscopy is reported. The devices are found to exhibit spatially varying response near exciton resonance, which cannot be explained by predicted effects such as Pockels and excitonic Stark effect. It is shown that the modulation signal is dominated by exciton linewidth broadening and narrowing associated with local accumulation and depletion of free holes. The field and frequency dependence of the devices is distinct from those of charge modulation devices. The observed behavior is ascribed to elastic scattering of excitons with field-driven intrinsic free carriers.

Stark effect and orbitals hybridization of moir\'e interlayer exciton in $ MoSe{2}/ WSe{2} $ heterobilayer.

“…In contrast, in-plane excitonic electro-optic has emerged as a contender among the experimental methods for obtaining brigth np states [4]. In addition, excitonic electro-optic effects offer several benefits in various application, such as on-chip electrooptic modulators [45,46]. In recent time, experiments have shown the layer hybridization of TMDs homobilayer and heterobilayer.…”

Simple Fabrication of Photodetectors Based on MoS2 Nanoflakes and Ag Nanoparticles

“…The fundamental properties of MoS 2 , such as quantum confinement effects and the functions of chalcogen vacancies and photoexcited carriers, have been extensively studied for their practical and potential applications [11][12][13][14][15]. Several electronic and optoelectronic devices, including field-effect transistors, charge-trap memories, and photodetectors based on mono-and multilayered MoS 2 , have been realized [16][17][18][19]. Interestingly, thin layers of MoS 2 with structural integrity exhibit high light-absorption coefficients, enabling sensitive photon detection via photoexcited carriers.…”

Contribution to Excitonic Linewidth from Free Carrier–Exciton Scattering in Layered Materials: The Example of hBN

“…In this paper, we focus our attention on one of these mechanisms, namely scattering with free carriers. This scattering mechanism can play an important part in determining the excitonic linewidth, especially in systems with a high density of free carriers and excitons [30], high pump fluences [31], in tunneling experiments [32,33], or when an electric field is applied to the semiconductor [34,35]. Additionally, electron exciton scattering processes also play an important role when studying exciton-polaron systems [36].…”