High-power monolithic narrow-linewidth 1.6 mJ/8 ns fiber laser system based on all-glass spun tapered double-clad fiber amplifier

TL;DR

This paper reports a high-power, narrow-linewidth nanosecond fiber laser system achieving 1.6 mJ pulses at 8 ns duration with high polarization, beam quality, and spectral purity, suitable for coherence-demanding applications.

Contribution

It demonstrates a high-energy, narrow-linewidth fiber laser system using all-glass spun tapered double-clad fibers without stimulated Brillouin scattering mitigation techniques.

Findings

Achieved 1.6 mJ pulses at 8 ns duration and 100 kHz repetition rate.

Delivered over 97.5% polarization and high beam quality (M2=1.3).

Spectral linewidth of 53.8 MHz with 160 W average power.

Abstract

High-energy, narrow-linewidth nanosecond pulses are highly demanding for many applications that require high temporal and spatial coherence. However, the amplification of narrow-linewidth pulses is primarily limited by stimulated Brillouin scattering, which causes pulse instabilities, back-reflected pulses, and catastrophic damage effects on optical components. In this work, we present a 1.6 mJ narrow-linewidth nanosecond pulsed fiber laser system based on all-glass spun tapered double-clad fibers without employing any mitigating technique for the stimulated Brillouin scattering effect. The system delivers pulses with an 8 ns duration at a 100 kHz repetition rate, over 97.5% degree of polarization, a beam quality factor of M2 = 1.3, a spectral linewidth of 53.8 MHz, a 160 W average power, and 188 kW peak power with a slope efficiency of 97.6%. The degree of spatial coherence of the amplified signal was measured to be 0.94. Our results are highly valued in applications requiring high-energy, high-coherence pulses with spectral, spatial, and polarization characteristics in a compact system.