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

Abstract

We report high-efficiency continuous-wave operation of a cryogenically cooled Fe2+:ZnSe laser at 4.167 µm using a four-slab configuration (2.75 mm each, 4.3-7.9 × 1018 cm−3) optimized for pump absorption and gain distribution. Cooled to 90 K and double-end pumped at 2.832 µm by two fiber-bulk hybrid Cr:ZnSe lasers (17 W and 13 W), the system achieved complete pump absorption (η<inf>a</inf> ≈ 99.68%), delivering 13.9 W output with 41% slope efficiency. Beam quality was near diffraction-limited (M2<inf>X</inf> = 1.13 ± 0.11, M2<inf>Y</inf> = 1.24 ± 0.12). The lasing wavelength red-shifted from 4.036 to 4.167 µm with power, attributed to thermal and gain-spectrum dynamics. This architecture mitigates thermal lensing and supports efficient mid-infrared power scaling. © 2025 Elsevier B.V., All rights reserved.