Contents I. Introduction
Compared with the focusing system of the prototype of SG-III laser facility, the focusing system under construction using large aperture wedged lens (WL) as separating harmonic components and target focusing lens[1], has finer focused beam pointing capability [2]. Because short wavelength laser is required in the inertial confinement fusion (ICF) experiments [3], [4], Nd:glass solid-state laser driver needs to convert the wavelength of 1053nm to or 351nm , and separate the remaining unconverted laser from the focused path so as to avoid the impact on the target pellet and the diagnostic equipment by the stray light[5]. Grating lens [6], [7] or WL[8] ~ [11] can both provide harmonic separation and focusing, and the manufacturing process of the WL is simpler than that of grating lens. WL can be seen as a combination of right-angle wedges and convexo-plane lens. There is a certain angle between the flat surface of WL and the incident beam, so the harmonic separation can be achieved. The back surface of WL is aspheric to accomplish beam focusing. By ray tracking the model of wedged lens focusing system (WLFS), we give and discuss the far-field patterns and motion curves of focusing beam under different incident conditions, which provides the theoretical basis for the system design, the optical adjustment and control method of the focusing system.
