3.3 W picosecond LWIR generation via ZnGeP₂ and BaGa₄Se₇ difference frequency generation

Area of Science:

• Nonlinear optics
• Laser physics
• Materials science

Background:

• Developing high-power sources for the long-wave infrared (LWIR) spectrum is crucial for various applications.
• Picosecond pulsed lasers offer advantages in nonlinear optical processes due to high peak powers.

Purpose of the Study:

• To demonstrate a high-power picosecond LWIR source.
• To achieve record average power for LWIR parametric sources beyond 10 μm.

Main Methods:

• Utilized type-II difference frequency generation (DFG) in ZnGeP2 (ZGP) and BaGa4Se7 (BGSe) crystals.
• Employed a 2089.1 nm laser at a 10 kHz repetition rate as the pump source.
• Integrated a double-pass optical parametric generator (OPG) for seeding the DFG process.

Main Results:

• Achieved a record tabletop 1.91 W idler output beyond 10 μm from BGSe DFG.
• Generated 2.84 W beyond 10 μm from the ZGP DFG stage alone.
• Boosted average power to 3.31 W by cascading ZGP and BGSe, yielding 5.9% optical-to-optical conversion efficiency.
• The LWIR source delivered 1.31 MW peak power with a 252.5 ps pulse duration.

Conclusions:

• The developed system represents the highest average power reported for LWIR parametric sources beyond 10 μm.
• The use of ZGP and BGSe crystals in a cascaded DFG configuration is effective for generating high-power LWIR radiation.
• This work paves the way for advanced applications requiring high-power, picosecond LWIR pulses.