Dynamic Control of Optical Response in Layered Metal Chalcogenide Nanoplates

Abstract

Tunable optical transitions in ultrathin layered 2-dimensional (2D) materials unveil the electronic structures of materials and provide exciting prospects for potential applications in optics and photonics. Here, we present our realization of dynamic optical modulation of layered metal chalcogenide nanoplates using ionic liquid (IL) gating over a wide spectral range. The IL gating significantly increased the tuning range of the Fermi level and, as a result, substantially altered the optical transitions in the nanoplates. Using heavily n-doped Bi2Se3 nanoplates, we substantially modulated the light transmission through the ultrathin layer. A tunable, high-transmission spectral window in the visible to near-infrared region has been observed due to simultaneous shifts of both the plasma edge and absorption edge of the material. On the other hand, optical response of multilayer MoSe2 flakes gated by IL has shown enhanced transmission in both positive and negative biases, which is consistent with their ambipolar electrical behavior. The electrically controlled optical property tuning in metal chalcogenide material systems provides new opportunities for potential applications, such as wide spectral range optical modulators, optical filters, and electrically controlled smart windows with extremely low material consumption.

2D Materials for Optical Modulation: Challenges and Opportunities

“…The optical responses of TMDs and black phosphorus are also sensitive to electrical gating. More recently, in MoSe 2 and Bi 2 Se 3 nanoplates, Liu et al observed dramatic gating voltage‐dependent transmission and reflection from near‐infrared to mid‐infrared . Meanwhile, TMDs have shown significant gate‐controlled nonlinear optical response, such as strong exciton charging effect‐induced second harmonic generation .…”

Excitation and propagation of surface plasmon polaritons on a non-structured surface with a permittivity gradient

“…With the rise of non-conventional plasmonic materials, such as transparent conductive oxides and heavily doped semiconductors 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , it has become possible to precisely control the permittivity distribution, thereby enabling new approaches for the excitation of SPPs. Conventionally, small fluctuations of permittivity have been considered as perturbations 14 , 25 or scatterers 26 .…”

“…In this paper, we show theoretically that the excitation and propagation of SPPs can be realized at a non-structured planar interface between a homogeneous dielectric and a gradient negative-permittivity material (GNM). With the development of advanced fabrication techniques, such as semiconductor doping 27 , electrical gating 23 , 24 , optical pumping 28 , 29 and metamaterials 30 , gradient permittivity materials can be readily obtained. Spatial gradients of permittivity can be achieved at various length scales, from deep subwavelength to the macroscopic scale.…”

Tunable metasurfaces for visible and SWIR applications

“…Liu et al demonstrated ionic liquid gating across Bi 2 Se 3 to show a great change in transmittance in the visible, as shown in Fig. 2c [59]. The transmittance varies over 60% in the visible with increasing gate voltage from − 1.5 V to 1.5 V. They figured out the dynamically tunable optical properties of Bi 2 Se 3 is originated from optical bandgap due to the change in free-electron concentration (Burstein-Moss shift).…”

“…Reproduced with permission from ©2019, Springer Nature. c Bi 2 Se 3 -based tunable absorber [59]. Reproduced with permission from ©2015, American Chemical Society the lack of inversion symmetry, the carriers in the valleys can be selectively excited or detected by circularly-polarized light (chiral behavior) [63,64], Because the carriers in 2D materials are strongly affected by electric gating field as well, the dielectric permittivities, especially chirality dependent Kerr permittivities also undergo strong change due to electrostatic gating.…”