Wavelength-tunable single longitudinal mode fiber optical parametric oscillator.

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Optics

Background:

• Fiber optical parametric oscillators (FOPOs) are crucial for generating tunable laser light.
• Achieving stable, single longitudinal mode (SLM) operation in FOPOs remains a challenge.
• Existing methods for SLM selection can be complex or introduce excess loss.

Purpose of the Study:

• To demonstrate a novel ring cavity fiber optical parametric oscillator (FOPO) capable of stable single longitudinal mode (SLM) operation.
• To utilize the unique properties of an unpumped erbium-doped fiber for effective mode selection.
• To characterize the performance of the developed SLM FOPO in terms of linewidth, tuning range, and stability.

Main Methods:

• A ring cavity FOPO was constructed incorporating a passive sub-ring cavity.
• An unpumped erbium-doped fiber (EDF) was integrated with an external fiber mirror for single mode selection.
• The EDF's saturable absorption characteristic was exploited to create a self-induced narrowband filter via counter-propagating wave interference.
• Laser performance was measured at a pump power of 31.2 dBm.

Main Results:

• Stable single longitudinal mode (SLM) operation was achieved with a narrow linewidth of 17.35 kHz.
• A tunable wavelength range of 3.8 nm (from 1536.5 nm to 1540.3 nm) was demonstrated.
• A high signal-to-noise ratio (SNR) of approximately 60 dB was maintained across the tuning range.
• The power stability of the SLM laser was measured to be 2.07 dB over a 30-minute period.

Conclusions:

• The proposed configuration effectively generates a stable single longitudinal mode fiber optical parametric oscillator.
• The use of an unpumped EDF as a self-induced filter provides a simple and efficient method for SLM selection in FOPOs.
• The demonstrated performance metrics indicate the potential of this SLM FOPO for various applications requiring narrow linewidth and tunable laser sources.