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Enhanced high-order harmonic generation for tunable comb-like THz spectra in PPLN
Optics Letters
|August 2, 2025
Summary
We demonstrate efficient generation of multicolor terahertz (THz) spectra using high-order harmonic quasi-phase-matching (QPM) in periodically poled lithium niobate. This novel THz source offers precise control over frequency and intensity for advanced spectroscopy and metrology.
Area of Science:
- Physics
- Optics
- Materials Science
Background:
- Terahertz (THz) spectroscopy and metrology require advanced light sources.
- Generating multicolor, comb-like THz spectra efficiently has been a challenge.
Purpose of the Study:
- To demonstrate efficient generation of multicolor, comb-like THz spectra.
- To explore the control over THz frequencies and harmonic intensities.
- To investigate the potential of this source for spectroscopy and metrology.
Main Methods:
- Utilizing high-order harmonic quasi-phase-matching (QPM) in periodically poled lithium niobate (PPLN).
- Employing optical rectification of near-infrared (NIR) laser pulses.
- Varying crystal temperature (15–350 K) and pump pulse duration (3 fs–50 fs).
Main Results:
- Efficient generation of multicolor, comb-like THz spectra spanning odd harmonics from 299 GHz to 2.41 THz.
- Precise control over central THz frequencies and harmonic intensities achieved by adjusting temperature and pulse duration.
- Up to ~10% frequency tunability in harmonic lines observed due to temperature-induced changes in refractive index.
Conclusions:
- The study successfully demonstrates a synchronized multicolor THz source with multioctave comb-like spectra.
- This method offers precise control over THz emission characteristics.
- The developed THz source holds significant promise for advanced applications in THz spectroscopy and metrology.
