Chinese Institute Achieves Progress in Mid-Infrared Laser Beam Combining

Researchers at the Shanghai Institute of Optics and Fine Mechanics (SIOM), part of the Chinese Academy of Sciences, have announced advancements in the spectral combination of high-power, continuous mid-infrared laser beams. Their work, published in Optics Letters, introduces a novel architecture that overcomes previous limitations in achieving high output power.

Mid-infrared lasers are crucial for applications ranging from gas detection and free-space communication to biomedical imaging and national security. Spectral beam combining is a key technique to increase laser power and expand its spectral range without degrading beam quality. However, traditional methods relying on large, single gratings face significant manufacturing challenges, especially at mid-infrared wavelengths, hindering the development of multi-channel, high-power systems.

The SIOM team proposed a 'Jigsaw-grating' spectral beam combining architecture. This design utilizes multiple smaller sub-gratings, distributed in an equivalent large-aperture space, to efficiently combine multiple mid-infrared laser beams. This approach circumvents the need for ultra-large single gratings, reducing manufacturing complexity and improving the scalability of multi-channel systems.

In their experimental validation, the team employed self-developed high-efficiency gold-coated mid-infrared gratings. They constructed a four-channel system combining OPO (optical parametric oscillator) lasers with central wavelengths tunable from 3.1 to 3.7 μm. The system achieved a combined output power of 50.8W with a grating combining efficiency of 92.1%, while maintaining good beam quality (Mx²=1.76, My²=1.46). This output power is reported as a high level for current 3-5 μm mid-infrared laser spectral combining results.

This research provides a new technical pathway for scaling mid-infrared multi-channel spectral beam combining systems from tens of watts to hundreds of watts. It also offers a reference for constructing high-power laser platforms across various spectral bands, from visible to terahertz.