Optically Controlling Broadband Terahertz Modulator Based on Layer-Dependent PtSe₂ Nanofilms.

Area of Science:

• Optoelectronics
• Materials Science
• Terahertz Technology

Background:

• Terahertz (THz) modulators are crucial for THz communication and imaging systems.
• Developing efficient and broadband THz modulators remains a significant challenge.
• Platinum Diselenide (PtSe₂) is an emerging material with tunable electronic properties.

Purpose of the Study:

• To investigate the performance of layer-dependent PtSe₂ nanofilms as optically controlled broadband terahertz modulators.
• To determine the optimal layer thickness of PtSe₂ for THz modulation.
• To characterize the modulation capabilities of PtSe₂ devices in the terahertz frequency range.

Main Methods:

• Fabrication of PtSe₂ nanofilms with varying layer numbers (3, 6, 10, 20 layers) on a high-resistance silicon substrate.
• Utilizing an optical pump and terahertz probe system to measure surface photoconductivity.
• Employing terahertz time-domain spectroscopy (THz-TDS) to evaluate broadband amplitude modulation.
• Applying Drude-Smith model fitting to extract material parameters like plasma frequency (ω) and scattering time (τ).

Main Results:

• A 3-layer PtSe₂ nanofilm exhibited superior surface photoconductivity compared to thicker films.
• The 3-layer film showed a higher plasma frequency (0.23 THz) and a lower scattering time (70 fs).
• Broadband amplitude modulation from 0.1-1.6 THz was achieved with a 3-layer PtSe₂ film, reaching a modulation depth of 50.9% at 2.5 W/cm² pump density.

Conclusions:

• PtSe₂ nanofilms, particularly the 3-layer variant, are highly suitable for optically controlled broadband terahertz modulators.
• The layer-dependent properties of PtSe₂ enable fine-tuning for optimal THz modulation performance.
• This research validates the potential of PtSe₂-based devices in advanced terahertz applications.