Laser physics studies with Phebus as part of the megajoule laser project

Experimental Observation of Near-Field Deterioration Induced by Stimulated Rotational Raman Scattering in Long Air Paths

“…[1−9] For the SG-III facility in the Laser Fusion Research Center, at the China Academy of Engineering Physics (CAEP), the propagation length 𝐿 between the output of the main amplifier and the frequency conversion system is 87 m and the mean intensity 𝐼 is around 2 GW/cm 2 , which induces an 𝐼𝐿 of 17.4 TW/cm. This figure goes far beyond the threshold reported before [1,2,5,6] describing the limit when the SRRS induces negative effects. In-depth investigation of the SRRS effect and suppression measurements is necessary.…”

“…The steady-state Raman gain efficient assumes 2.5 cm/TW. [1,2,6] From Figs. 1 and 2, after 85 m air path propagation of a 1053-nm, linearly polarized, a 3-ns square laser pulse with a uniform near field and an initial average fluence of 6 J/cm 2 , the average fluence decreases to ∼3 J/cm 2 , with an energy loss up to 50%.…”

Temporal, Spectral and Spatial Characterization of High-Energy Laser Pulse with Small Bandwidth Propagating through Long Path

“…Further studies in LMJ point out that the IL production must be less than 13.2 TW/cm to suppress SRRS. [4] In our previous studies, [14] we observed intense speckle pattern of near-field with thickly dotted hot spots when IL production is above 17 TW/cm, resulting from the combination of the nonlinear Raman amplification and the linear diffraction propagation effect of the Stokes with a noise pattern arising from the spontaneous Raman scattering. With the construction of the new laser facility, energy of 3 ns pulse has already reached 7500 J, and the propagation distance has exceeded 80 m as well, which means an IL production of about 16.4 TW/cm.…”