Surface Optical Rectification from Layered MoS₂ Crystal by THz Time-Domain Surface Emission Spectroscopy

Abstract

Surface optical rectification was observed from the layered semiconductor molybdenum disulfide (MoS) crystal via terahertz (THz) time-domain surface emission spectroscopy under linearly polarized femtosecond laser excitation. The radiated THz amplitude of MoS has a linear dependence on ever-increasing pump fluence and thus quadratic with the pump electric field, which discriminates from the surface Dember field induced THz radiation in InAs and the transient photocurrent-induced THz generation in graphite. Theoretical analysis based on space symmetry of MoS crystal suggests that the underlying mechanism of THz radiation is surface optical rectification under the reflection configuration. This is consistent with the experimental results according to the radiated THz amplitude dependences on azimuthal and incident polarization angles. We also demonstrated the damage threshold of MoS due to microscopic bond breaking under the femtosecond laser irradiation, which can be monitored via THz time-domain emission spectroscopy and Raman spectroscopy.

Nonlinear optics of two‐dimensional transition metal dichalcogenides

“…NLO of TMDs also shows some potential applications in several new directions such as THz technology, optical limiting, and quantum NLO. Huang et al demonstrated that few layer MoS 2 can generate THz radiation from 0.1 to 3.5 THz efficiently under 800 nm fs‐laser excitation, which is ascribed to the second‐order nonlinear optical process—surface optical rectification . Optical limiting mainly arises from the TPA and it has been demonstrated in TMDs.…”

“…Huang et al demonstrated that few layer MoS 2 can generate THz radiation from 0.1 to 3.5 THz efficiently under 800 nm fs-laser excitation, which is ascribed to the second-order nonlinear optical process-surface optical rectification. 178 Optical limiting mainly arises from the TPA and it has been demonstrated in TMDs. The optical limiting performance is dependent on the layer number and the excitation wavelength due to the layer number dependent band gap.…”

Nonlinear Optics with 2D Layered Materials

“…Research on THz technologies with 2DLMs has attracted huge interest. In contrast to numerous fascinating theoretical concepts proposed on THz generation in graphene, currently the main experimental demonstrations still concentrate on bulk materials (e.g., thick‐layer graphite, topological insulators, thick‐layer MoS 2 , and WS 2 ). There are only a few experimental demonstrations with monolayer and few‐layer graphene for ultrafast, broadband, and cost‐effective THz light emission .…”

Photosensitive Complementary Inverters Based on n‐Channel MoS2 and p‐Channel MoTe2 Transistors for Light‐to‐Frequency Conversion Circuits

“…[1][2][3][4][5] This is owing to excellent electrostatic gate coupling, the absence of surface dangling bonds, the high effective mass of electrons as compared with Si, and other properties. [3][4][5][6][7][8][9] Among a variety of electronic opportunities for TMDCs, novel optical applications can be triggered by the unique properties of TMDCs such as bandgap tunability depending on the number of TMDC layers, [10][11][12] easy preparation of a few layers with single crystallinity, preferable formation of heterostructures due to the multistacking scheme, affordable fieldeffect mobility, and excellent mechanical properties. [1] For the application of optical sensors, ultralow power consumption and high noise-to-signal ratio are highly required.…”