High-pulse-energy and high-efficiency 1.9  µm Raman laser

In this work, a 1.9 µm laser was generated in the pressurized hydrogen pumped by a 1064 nm pulsed laser via stimulated Raman scattering. By the optimization of hydrogen pressure, focusing methods, and the pass number of the multi-pass cell, 199.8 mJ of Raman laser was achieved with f =1000mm cylindrical focal lens, the five-pass configuration, and 0.75 MPa hydrogen pressure. The corresponding photon conversion efficiency (PCE) was 82.7%, the energy conversion efficiency was 46.2%, the pulse width was 9.6 ns, and the maximum peak power was 20.8 MW. Moreover, the maximum PCE reached 86.5% at a hydrogen pressure of 1 MPa. Simulations showed that the application of a square pumped beam was helpful to increase Raman laser energy and PCE. In addition, the beam quality of M x 2 =2.6 and M y 2 =2.4 exhibited excellent spatial beam quality. This combination of high efficiency and excellent beam quality confirms the effectiveness of the parametric optimization strategy for gas-phase Raman lasers.