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Optimizing multi-cycle THz generation in PPLN: the role of central frequency and temperature
Optics Letters
|October 1, 2025
Summary
Optimizing terahertz (THz) pulse generation in periodically poled lithium niobate (PPLN) depends on balancing frequency scaling and absorption. Lower temperatures favor higher frequencies near 1 THz for peak efficiency.
Area of Science:
- Optics and Photonics
- Condensed Matter Physics
- Materials Science
Background:
- Efficient generation of multi-cycle (MC) terahertz (THz) pulses is crucial for applications in nonlinear spectroscopy and ultrafast photonics.
- Periodically poled lithium niobate (PPLN) is a key material for nonlinear optical processes, including THz generation.
- Understanding the influence of operational parameters like frequency and temperature on THz generation efficiency in PPLN is essential for device optimization.
Purpose of the Study:
- To experimentally investigate the impact of central THz frequency and crystal temperature on MC THz pulse generation efficiency in PPLN.
- To identify the optimal operating conditions for maximizing THz generation efficiency by analyzing the interplay between frequency scaling and absorption.
Main Methods:
- Comprehensive evaluation of six different PPLN samples was conducted.
- THz generation efficiency was measured across various central THz frequencies and at cryogenic (15 K) and room temperatures (295 K).
- The relationship between conversion efficiency, central frequency, temperature, and material absorption was analyzed.
Main Results:
- A significant interplay between quadratic frequency scaling and absorption effects was observed, governing optimal THz generation.
- At cryogenic temperatures (15 K), peak conversion efficiency occurred near 1 THz, balancing frequency scaling and minimized phonon-induced absorption.
- At room temperature (295 K), strong absorption around 7.4 THz shifted the optimal frequency down to 0.5 THz.
Conclusions:
- Optimal THz generation in PPLN is highly dependent on the operating temperature and central frequency due to competing effects.
- Cryogenic temperatures enable efficient THz generation at higher frequencies (around 1 THz) by mitigating absorption losses.
- These findings provide guidance for upscaling narrowband THz sources for advanced spectroscopic and photonic applications.
