Pulse sequences for efficient multi-cycle terahertz generation in periodically poled lithium niobate

Area of Science:

• Nonlinear Optics
• Terahertz (THz) Science and Technology

Background:

• Generating high-energy, high-peak-power, multi-cycle terahertz (THz) pulses is crucial for various scientific applications.
• Existing methods face limitations due to laser-induced damage and lower conversion efficiencies.

Purpose of the Study:

• To propose and investigate the use of laser pulse sequences for cascaded difference frequency generation of THz pulses.
• To achieve unprecedented optical-to-terahertz energy conversion efficiencies and high peak electric fields.

Main Methods:

• Detailed simulations of coupled nonlinear interactions between optical and THz waves.
• Analysis of cascaded difference frequency generation in cryogenically cooled periodically poled lithium niobate.
• Numerical calculations incorporating self-phase-modulation, cascaded second harmonic generation, and laser-induced damage.

Main Results:

• Achieved optical-to-terahertz energy conversion efficiencies greater than 5%.
• Demonstrated capability to generate THz pulses with peak electric fields of hundreds of MV/m and durations of hundreds of picoseconds.
• Circumvented laser-induced damage limitations for Joule-level pumping, enabling THz pulse energies exceeding 10 mJ.

Conclusions:

• Laser pulse sequences offer a viable route to high-energy, high-peak-power multi-cycle THz sources.
• Optimizing poling period and reducing absorption can further enhance energy conversion efficiencies beyond 10%.
• The study provides analytic formulations and parameter optimization for efficient THz generation in the 0.1-1 THz range.