Waveguide-integrated mid-IR photodetector and all-optical modulator based on interlayer excitons absorption in a...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Two-dimensional (2D) van der Waals semiconductors enable bandgap engineering for advanced photonic devices through heterostructure formation.
• Type II band structures in these heterostructures lead to ultrafast charge transfer and the formation of interlayer excitons (ILEs).

Purpose of the Study:

• To demonstrate, for the first time, a waveguide-coupled photodetector and modulator in the mid-infrared (mid-IR) spectrum utilizing ILE absorption.
• To explore the potential of 2D heterostructures for integrated photonic applications.

Main Methods:

• Fabrication of a heterostructure device comprising single-layer tungsten disulfide (WS₂) and few-layer hafnium disulfide (HfS₂).
• Integration of the heterostructure with a silicon waveguide on a sapphire substrate.
• Characterization of photodetection and all-optical modulation properties in the mid-IR range.

Main Results:

• Achieved broadband mid-IR photodetection spanning 3.8-5.5 µm with responsivity in the tens of µA/W.
• Demonstrated no significant impact on the waveguide's transmission during photodetection.
• Successfully implemented waveguide-integrated, mid-IR all-optical modulation by controlling ILE population via interband transitions.

Conclusions:

• The developed WS₂/HfS₂ heterostructure is a promising platform for mid-IR photonic devices.
• The device enables efficient photodetection and all-optical modulation, paving the way for novel integrated optoelectronic applications.