Cascade gaseous Raman laser at 2.6 μm in sequential multiple-pass cells

We reported a cascade gaseous stimulated Raman scattering (SRS) laser for efficient generation of 2.6 μm mid-infrared radiation. The system employed two sequential seven-pass cells. A 1064 nm Nd:YAG pump laser was first converted to 1907 nm first-Stokes radiation in a H₂-filled cell. This output then served as the pump for a second cell filled with CO₂, generating the final output at 2594 nm. This dual-cell configuration effectively extended the wavelength to the targeted spectral region. Optimized operation with 0.20 MPa H₂ and 0.3 MPa CO₂ yielded a 21.6 mJ 2594 nm laser from 124 mJ of 1907 nm pump energy, corresponding to a PCE of 23.7% and peak power of 2.63 MW. The beam quality factor (M²) of the 2594 nm output was measured to be 2.46. This work presents an effective technical route for producing high-peak-power MIR lasers.