All-Optical Two-Color Terahertz Emission from Quasi-2D Nonlinear Surfaces

Area of Science:

• Condensed matter physics
• Nonlinear optics
• Terahertz (THz) science and technology

Background:

• Two-color terahertz (THz) generation is crucial for various applications.
• Existing methods face challenges due to the lack of phase matching in condensed matter systems.
• Efficient THz generation requires overcoming these phase-matching limitations.

Purpose of the Study:

• To demonstrate a phase-matching-free method for two-color THz generation in condensed matter.
• To explore the use of a highly resonant absorptive system for enhanced THz conversion.
• To investigate the underlying third-order nonlinear interaction and its dependence on optical field phases.

Main Methods:

• Utilizing a third-order nonlinear interaction localized at the surface of a narrow-band-gap semiconductor.
• Employing a highly resonant absorptive system to facilitate phase-matching-free THz generation.
• Analyzing the relative phase dependence between the optical pulse and its second harmonic.

Main Results:

• Successfully achieved phase-matching-free two-color THz generation in condensed matter.
• Demonstrated that the THz conversion efficiency depends directly on the relative phase of the interacting optical fields.
• Isolated the third-order nonlinear effect from other competing THz-emitting surface mechanisms.

Conclusions:

• The proposed method overcomes the phase-matching limitations in condensed matter THz generation.
• The highly resonant absorptive system enables efficient two-color THz conversion via third-order nonlinearity.
• This work provides a new pathway for advanced THz applications in condensed matter physics.