Terahertz radiation from propagating acoustic phonons based on deformation potential coupling

Area of Science:

• Condensed Matter Physics
• Materials Science
• Terahertz (THz) Photonics

Background:

• Terahertz (THz) electromagnetic waves are crucial for various applications, including spectroscopy and imaging.
• Current THz emission mechanisms often rely on piezoelectric effects, limiting material choices and device designs.
• Understanding novel THz generation pathways is essential for advancing THz technology.

Purpose of the Study:

• To investigate a new mechanism for THz electromagnetic emission in non-polar silicon.
• To explore the role of deformational coupling between acoustic phonons and electrons.
• To analyze the influence of transducer layer thickness on THz emission characteristics.

Main Methods:

• Utilized a Gallium Phosphide (GaP) transducer layer with nanoscale thickness variation (16-45 nm).
• Generated acoustic phonon pulses propagating into a silicon medium.
• Analyzed the modulation of the silicon bandgap by acoustic pulses and subsequent THz emission.
• Correlated experimental observations with theoretical calculations based on deformational potential coupling.

Main Results:

• Demonstrated THz electromagnetic emission via deformational coupling of acoustic phonons and electrons in silicon, without piezoelectricity.
• Observed time-delayed THz bursts generated by propagating acoustic pulses modulating the silicon bandgap.
• Emission amplitude analysis aligned with theoretical models considering mobile charge carrier density and phonon-induced deformation.

Conclusions:

• Established a novel THz emission mechanism in silicon based on deformational potential coupling.
• This mechanism offers a distinct pathway for THz wave generation, complementary to piezoelectric effects.
• The findings provide new insights into THz generation in semiconductors and potential for new device architectures.