Design and performance of final optics assembly in SG-II Upgrade laser facility

Abstract

In high power laser facility for inertial confinement fusion research, final optics assembly (FOA) plays a critical role in the frequency conversion, beam focusing, color separation, beam sampling and debris shielding. The design and performance of FOA in SG-II Upgrade laser facility are mainly introduced here. Due to the limited space and short focal length, a coaxial aspheric wedged focus lens is designed and applied in the FOA configuration. Then the ghost image analysis, the focus characteristic analysis, the B integral control design and the optomechanical design are carried out in the FOA design phase. In order to ensure the FOA performance, two key technologies are developed including measurement and adjustment technique of the wedged focus lens and the stray light management technique based on ground glass. Experimental results show that the design specifications including laser fluence, frequency conversion efficiency and perforation efficiency of the focus spot have been achieved, which meet the requirements of physical experiments well.

School of Mechanical Engineering, Shanghai Jiao Tong University, 200240, Shanghai, China

“…Transport of ultra-intense lasers in plasmas in different density ranges is crucial both in fundamental researches of laser-plasma physics and diverse applications, including particle acceleration [1,2], brilliant X-ray emission [3,4], relativistic electrons generation [5,6], and inertial confinement fusion (ICF) [7][8][9]. In recent laser-plasma experiments, the laser beams with normalized field strength reaches a > 1 and even a ≫ 1 (a = eE/mcω) have been widely adopted [10][11][12], where e and m are electron charge and mass, and ω and c are laser frequency and speed in vacuum. In such a laser field, the intrinsic relativistic nonlinearity would lead to the well-known relativistic transparency (RT) effect [13,14], where γm (γ is the Lorentz factor) increases, and over-dense plasmas could not shield the laser field.…”

Research on spatial filter lens auxiliary adjustment system in high power laser facility

“…The spatial filter is composed of two confocal lenses and small holes. In the debugging process, the small hole is taken as the observation reference, and the three-dimensional translation and two-dimensional angle of the incident lens are adjusted to realize the spatial frequency filtering function and also constitute the reference of the spatial filter [12][13][14][15] ; similarly, the collimating lens of the spatial filter also needs the adjustment of the three-dimensional translation and two-dimensional angle to realize the light beam collimation. In short, the spatial filter constitutes the optical axis of the high-power laser device.…”

Rapid Growth of a Cuboid DKDP (KDxH2–xPO4) Crystal

“…DKDP (KD x H 2‑x PO 4 ) is the best nonlinear crystal used as a tripler in inertial confinement fusion (ICF) facilities, because this crystal can minimize stimulated Raman scattering. , It takes 1–2 years to get a DKDP tripler for ICF facilities using a traditional growth method; therefore, the development of a rapid growth method is important. , In a “point-seed” rapidly grown DKDP crystal, all prismatic and pyramidal crystallographic faces grow. Where these two crystallographic faces are next to each other, a pyramid–prism (PY–PR) boundary appears. , Using orthogonal polarization interferometry, the abrupt Δ­( n e – n o ) distribution near the PY–PR boundary was clearly identified .…”

“…1,2 It takes 1−2 years to get a DKDP tripler for ICF facilities using a traditional growth method; therefore, the development of a rapid growth method is important. 3,4 In a "point-seed" rapidly grown DKDP crystal, all prismatic and pyramidal crystallographic faces grow. Where these two crystallographic faces are next to each other, a pyramid−prism (PY−PR) boundary appears.…”