Coherent combination of mid-IR laser beams using a Sagnac-type interferometer

Area of Science:

• Optics and Photonics
• Laser Physics
• Fiber Optics

Background:

• Mid-infrared (mid-IR) lasers are crucial for various applications, including spectroscopy and remote sensing.
• Scaling output power of fiber lasers, especially in the mid-IR, remains a significant challenge.
• Coherent beam combination (CBC) offers a promising pathway for high-power laser generation.

Purpose of the Study:

• To develop and demonstrate a high-efficiency coherent beam combination (CBC) system for mid-infrared fiber lasers.
• To investigate the performance of the CBC system under both continuous-wave (CW) and ultrafast pulsed operation.
• To assess the potential for power scaling of mid-IR CW and ultrafast fiber lasers using the proposed Sagnac-type CBC setup.

Main Methods:

• Implementation of a Sagnac-type interferometer utilizing two fluoride fiber amplifiers.
• Operation and characterization of the CBC system at a 2.8 µm wavelength.
• Testing under continuous-wave (CW) and picosecond-pulse (1-ps) laser conditions.

Main Results:

• Achieved >90% combination efficiency for CW operation, delivering 2.8 W output power with M² <1.2.
• Demonstrated amplification and temporal compression of 1-ps pulses to ~170 fs.
• Obtained ~84% CBC efficiency for amplified ultrafast laser beams, resulting in ~1 W recombined power.

Conclusions:

• The Sagnac-type CBC system demonstrates high efficiency for both CW and ultrafast mid-IR fiber lasers.
• The setup shows significant potential for power scaling of fiber laser sources in the 2.8 µm spectral region.
• This approach is a viable method for generating high-power mid-IR laser output.