High-efficiency, kilowatt 1034  nm all-fiber amplifier operating at 11  pm linewidth

Area of Science:

• Laser Physics
• Fiber Optics
• Materials Science

Background:

• High-power fiber amplifiers are crucial for various applications, including laser material processing and scientific research.
• Yb-doped silica fiber amplifiers offer efficient operation at wavelengths suitable for many industrial and research needs.
• Stimulated Brillouin scattering (SBS) is a major limitation in power scaling fiber amplifiers, necessitating effective suppression techniques.

Purpose of the Study:

• To investigate power scaling of a monolithic Yb-doped fiber amplifier at 1034 nm.
• To compare the effectiveness of white noise source (WNS) and pseudo-random bit sequence (PRBS) phase modulation for SBS suppression.
• To demonstrate high-power, near-diffraction-limited beam quality from the amplifier.

Main Methods:

• Utilized a monolithic Yb-doped fiber amplifier architecture.
• Implemented optical linewidth broadening via WNS and PRBS phase modulation schemes to suppress SBS.
• Performed power measurements, slope efficiency calculations, and beam quality assessments (e.g., M²).

Main Results:

• Achieved 1 kW output power with 81% slope efficiency using PRBS modulation at 3.5 GHz clock rate.
• Demonstrated near-diffraction-limited beam quality (M² ≈ 1) with no modal instability.
• Observed significantly lower power (470 W) with WNS modulation at comparable linewidth and fiber length.
• Reported the highest power (1 kW) for a spectrally narrow (11 pm) all-fiber Yb-doped amplifier in this wavelength range.

Conclusions:

• PRBS phase modulation is a highly effective technique for suppressing SBS and enabling significant power scaling in Yb-doped fiber amplifiers.
• The demonstrated kilowatt-class amplifier offers excellent beam quality, making it suitable for demanding beam combining applications.
• This work represents a significant advancement in spectrally narrow, high-power all-fiber laser technology.