Precise parameter control of multicycle terahertz generation in PPLN using flexible pulse trains.

Area of Science:

• Nonlinear optics
• Terahertz (THz) science and technology
• Laser physics

Background:

• Low conversion efficiencies in nonlinear optical down-conversion limit the generation of high-energy, high-field terahertz (THz) radiation.
• Existing scientific fields require narrowband, multicycle THz pulses, which are hindered by current generation efficiencies.

Purpose of the Study:

• To experimentally optimize the nonlinear optical down-conversion process for generating THz frequencies.
• To systematically explore parameter dependences for optical-to-THz difference-frequency generation.
• To develop practical, high-field, efficiency-optimized THz sources.

Main Methods:

• Implementation of a customized optical laser system producing highly-tunable infrared pulse trains.
• Systematic experimental exploration and optimization of the down-conversion process.
• Tuning of pulse energy, duration, number, and periodicity to test theoretical predictions.

Main Results:

• Demonstrated a pathway to significantly higher conversion efficiencies than previously achieved.
• Provided precise mapping of nonlinear crystal medium properties.
• Identified agreements and deviations between experimental results and theoretical simulations.

Conclusions:

• The study offers insights into the limitations of existing theories for optical-to-THz conversion.
• Experimental results provide foundational steps for developing efficient, high-field THz sources.
• Optimized laser systems are crucial for advancing THz generation capabilities.