Generation of five phase-locked harmonics by implementing a divide-by-three optical frequency divider

Area of Science:

• Optics and Photonics
• Quantum Optics

Background:

• High harmonic generation (HHG) is a crucial nonlinear optical process for producing coherent extreme ultraviolet and X-ray radiation.
• Precise control over the spectral content and phase relationships of HHG is essential for advanced applications.

Purpose of the Study:

• To demonstrate the generation of multiple phase-locked harmonics with a precise integer frequency ratio.
• To implement a novel optical frequency division technique within the HHG process.

Main Methods:

• Utilized a divide-by-three optical frequency divider integrated into the high harmonic generation setup.
• Employed femtosecond laser pulses to drive the nonlinear process.

Main Results:

• Successfully generated five phase-locked harmonics (f₁, f₂, f₃, f₄, f₅) with wavelengths 2403 nm, 1201 nm, 801 nm, 600 nm, and 480 nm, respectively.
• Achieved an exact 1:2:3:4:5 frequency ratio among the generated harmonics.
• Confirmed coaxial generation and high phase coherence in both time and space for all five harmonics.

Conclusions:

• The integration of an optical frequency divider enables precise control over harmonic generation, yielding a precise frequency comb.
• The generated phase-coherent, multi-wavelength light source has significant potential for applications in spectroscopy, metrology, and ultrafast science.