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

Area of Science:

• Solid-state physics
• Materials science
• Optoelectronics

Background:

• Layered semiconductors like molybdenum disulfide (MoS2) are promising for advanced electronic and optoelectronic applications.
• Terahertz (THz) radiation generation and detection are crucial for various scientific and technological fields.
• Understanding nonlinear optical phenomena in low-dimensional materials is key to novel device development.

Purpose of the Study:

• To investigate and confirm surface optical rectification in molybdenum disulfide (MoS2) crystals.
• To elucidate the underlying mechanism of THz radiation generation in MoS2.
• To determine the damage threshold of MoS2 under femtosecond laser irradiation.

Main Methods:

• Terahertz (THz) time-domain surface emission spectroscopy was employed.
• Linearly polarized femtosecond laser excitation was used.
• Raman spectroscopy was utilized to monitor material damage.

Main Results:

• Surface optical rectification was observed in MoS2, with THz amplitude linearly dependent on pump fluence (quadratically on electric field).
• The observed THz radiation mechanism in MoS2 differs from surface Dember effect in InAs and transient photocurrent in graphite.
• Experimental results align with theoretical analysis based on MoS2 crystal symmetry and surface optical rectification under reflection configuration.
• The damage threshold of MoS2 was demonstrated and monitored via THz emission and Raman spectroscopy.

Conclusions:

• Surface optical rectification is the primary mechanism for THz generation in MoS2 under the studied conditions.
• MoS2 exhibits unique THz radiation properties distinct from other semiconductors and materials.
• THz time-domain emission spectroscopy is a viable tool for monitoring laser-induced damage in MoS2.