Efficient high-power continuous-wave multi-slab Fe:ZnSe laser at 4.1 μm.

Area of Science:

• Mid-infrared laser technology
• Solid-state laser development
• Materials science for optoelectronics

Background:

• Efficient mid-infrared (MIR) lasers are crucial for various applications, including spectroscopy, free-space communications, and medical diagnostics.
• Iron-doped zinc selenide (Fe2+:ZnSe) crystals are promising gain media for MIR lasers due to their broad emission bandwidth.
• Challenges in MIR laser development include thermal management and achieving high power output.

Purpose of the Study:

• To report high-efficiency continuous-wave (CW) operation of a cryogenically cooled Fe2+:ZnSe laser.
• To investigate a novel four-slab configuration for optimized pump absorption and gain distribution.
• To demonstrate efficient mid-infrared power scaling and assess beam quality.

Main Methods:

• Utilized a four-slab Fe2+:ZnSe configuration (2.75 mm each) with a doping concentration of 4.3–7.9 × 10^18 cm^-3.
• Cooled the laser system to 90 K for optimal performance.
• Employed double-end pumping at 2.832 µm using two fiber-bulk hybrid Cr:ZnSe lasers (17 W and 13 W).

Main Results:

• Achieved complete pump absorption (ηa ≈ 99.68%) and delivered 13.9 W of output power.
• Obtained a high slope efficiency of 41%.
• Demonstrated near diffraction-limited beam quality (Mx²=1.13±0.11, My²=1.24±0.12) and observed wavelength red-shift from 4.036 to 4.167 µm with increasing power.

Conclusions:

• The cryogenically cooled Fe2+:ZnSe laser in a four-slab configuration provides high efficiency and good beam quality.
• The architecture effectively mitigates thermal lensing, enabling efficient mid-infrared power scaling.
• This approach advances the development of powerful and reliable MIR laser sources.