Theory of terahertz generation by optical rectification using tilted-pulse-fronts

Area of Science:

• Physics
• Optics
• Nonlinear Optics

Background:

• Terahertz (THz) generation via optical rectification is crucial for spectroscopy and imaging.
• Tilted-pulse-front techniques offer a pathway to high-energy THz pulses.
• Understanding the complex interplay of factors limiting THz generation is essential for source development.

Purpose of the Study:

• To develop a comprehensive model for THz generation using tilted-pulse-fronts.
• To investigate the spatio-temporal dynamics of optical pump pulses during THz generation.
• To identify key factors affecting energy scaling and conversion efficiency.

Main Methods:

• Development of a two-dimensional (2-D) model accounting for spatio-temporal pulse variations.
• Inclusion of nonlinear coupled interactions between optical and THz fields.
• Consideration of self-phase modulation and stimulated Raman scattering.
• Validation against experimental data and analytical calculations.

Main Results:

• The model accurately predicts THz generation, validated by experiments.
• Optical pump pulses broaden spectrally and in transverse momentum (kx) during THz generation.
• Group velocity dispersion leads to spatio-temporal pulse break-up, limiting further THz generation.
• Significant trade-offs exist between THz spatial/spectral properties and conversion efficiency.

Conclusions:

• The study highlights limitations in energy scaling for THz generation with tilted-pulse-fronts.
• Elliptical pump pulse profiles are suggested for higher optical pump energies.
• Optimization requires careful consideration of optical pump conditions and resulting THz radiation characteristics.