Stable single-frequency traveling-wave fiber loop laser with integral saturable-absorber-based tracking narrow-band...

Area of Science:

• Photonics and Optics
• Laser Physics
• Materials Science

Background:

• Erbium-doped fiber lasers are crucial for telecommunications and spectroscopy.
• Achieving stable single-frequency and polarization operation is challenging due to environmental factors.
• Existing methods often lack automatic wavelength tracking and narrow bandwidth control.

Purpose of the Study:

• To demonstrate stable single-frequency and polarization operation of a traveling-wave, erbium-doped fiber loop laser.
• To investigate the role of an unpumped Er3+-doped fiber section as a saturable absorber.
• To characterize the laser's output power, noise, and linewidth.

Main Methods:

• Incorporation of an unpumped Er3+-doped fiber section acting as a saturable absorber.
• Utilizing a narrow-band feedback reflector to enhance spectral purity.
• Testing the laser with launched pump powers at 1064 nm and measuring output at 1535 nm.
• Characterizing relative intensity noise and laser linewidth.

Main Results:

• Stable single-frequency and polarization operation was successfully demonstrated.
• Output powers of up to 6.2 mW were achieved at 1535 nm for 175 mW pump power.
• Relative intensity noise was below -112 dB/Hz above 200 kHz.
• Laser linewidth was measured to be less than 0.95 kHz.
• Slow frequency drift (~170 MHz/h) was observed due to environmental influences.

Conclusions:

• The proposed method effectively ensures single-frequency operation by employing a self-tracking saturable absorber.
• The Er3+-doped fiber loop laser exhibits excellent performance characteristics, including high output power and low noise.
• Further stabilization against environmental factors is needed for applications requiring extreme frequency stability.