A Circular Photogalvanic Effect-Controlled Polarimeter based on a Bipolar Phototransistor Utilized in Spatially...

Area of Science:

• Optoelectronics
• Materials Science
• Condensed Matter Physics

Background:

• The circular photogalvanic effect (CPGE) detects circularly polarized light but typically yields weak signals.
• Existing methods often require auxiliary amplifiers, limiting practical applications.

Purpose of the Study:

• To develop a device capable of detecting and amplifying CPGE photocurrents without external amplification.
• To create a sensitive polarimeter for circularly polarized light.

Main Methods:

• Fabrication of a vertical bipolar phototransistor using a MoS₂/ZrGeTe₄/MoS₂ heterojunction with a noncentrosymmetric active region.
• Characterization of CPGE responsivity and gain.
• Spatially resolved mapping of near-infrared (NIR) vortex beams.

Main Results:

• Achieved a CPGE gain of 25.
• Demonstrated CPGE responsivity of tens of μA/W from visible to NIR wavelengths.
• Exhibited wide acceptance angles (-45° to 45°) at room temperature.
• Successfully utilized the device as a sensitive polarimeter for NIR vortex beams.

Conclusions:

• The developed heterojunction phototransistor effectively detects and amplifies CPGE photocurrents.
• The device functions as a highly sensitive, self-amplifying polarimeter.
• This approach offers a pathway for nanostructured polarimeters without external amplification for nanophotonics and optoelectronics.