Narrow-linewidth fiber amplifier for gravitational-wave detectors

Area of Science:

• Laser Physics
• Optical Engineering
• Astrophysics Instrumentation

Background:

• Gravitational-wave (GW) interferometric detectors require highly stable and low-noise laser sources.
• Existing laser technologies face limitations in power scaling and noise performance for next-generation GW observatories.

Purpose of the Study:

• To design and characterize a narrow-linewidth Ytterbium-doped fiber amplifier for GW detection.
• To achieve high output power (up to 178 W) at 1064 nm with excellent beam quality.
• To evaluate the amplifier's free-running noise performance against stringent GW detector requirements.

Main Methods:

• Utilized a specialty large-mode-area Ytterbium-doped fiber with confined-core doping and depressed cladding for amplification.
• Incorporated a smaller-core passive fiber post-amplification to enhance output beam quality.
• Measured the free-running noise spectrum of the fiber amplifier system.

Main Results:

• Achieved a maximum output power of 178 W at 1064 nm.
• Demonstrated a narrow-linewidth emission suitable for interferometric applications.
• The measured free-running noise levels were found to be equal to or better than current Advanced LIGO noise requirements.

Conclusions:

• The developed Ytterbium-doped fiber amplifier is a promising candidate for future gravitational-wave detectors.
• The novel fiber design effectively balances high power, good beam quality, and low noise.
• Further improvements are discussed for long-term operational stability and integration into GW observatories.