Enhanced second-harmonic generation with four-wave-mixing broadened fundamental laser

Area of Science:

• Optics and Photonics
• Laser Physics
• Nonlinear Optics

Background:

• Single-pass second-harmonic generation (SHG) is crucial for high-power, continuous-wave, narrow-linewidth visible lasers.
• Improving conversion efficiency in SHG schemes remains a significant challenge.

Purpose of the Study:

• To demonstrate enhanced single-pass SHG conversion efficiency.
• To overcome limitations in conventional phase-modulated laser schemes for visible laser generation.

Main Methods:

• Utilizing four-wave-mixing (FWM) to broaden the spectrum of phase-modulated fundamental lasers.
• Co-amplifying two phase-modulated seeds in an ytterbium-doped fiber amplifier.
• Employing cascaded FWM to redistribute power into multimode spectra.

Main Results:

• Achieved 1.52 times higher efficiency compared to conventional phase-modulated laser schemes in sum-frequency generation (SFG).
• Generated a green laser with up to 76.9 W output power at 531.5 nm.
• Reached a conversion efficiency of 24.2% while maintaining relative intensity noise (RIN) below -120 dBc/Hz above 2 kHz.

Conclusions:

• The FWM-broadened fundamental laser approach offers a robust method for high-power visible laser generation.
• This technique provides a straightforward route to achieving high-power, low-noise visible lasers.
• The demonstrated method enhances SHG conversion efficiency significantly.