Experimental demonstration of polarization smoothing in a convergent beam

Abstract

We report an experimental demonstration of polarization smoothing by using a specially cut KDP plate in the convergent ultraviolet (351 nm wavelength) section of a high-power laser system. A 410 mm×410 mm×10 mm sized KDP plate placed after the final focus lens successfully reduced the focal spot intensity contrast to 75.6%, which is in good agreement with the theoretical expectation. In our experiment, no obvious transverse stimulated scattering was observed with the maximum 351 nm laser energy of 4032 J/3 ns, thus indicating the operation safety margin of our laser system.

Laser performance of the SG-III laser facility

“…Beam smoothing techniques, such as continuous phase plate (CPP), smoothing by spectral dispersion (SSD) [14,15] and polarization smoothing (PS) [16][17][18] , are all adopted in SG-III. When CPP and SSD are both used, the focal spot is obviously smoothed and the nonuniformity of the focal spot is reduced from 1.21 to 0.27 ( Figure 13).…”

“…PS can further smooth the focal spot by a factor of 0.717 theoretically. A KDP plate is used in the focusing beam section in SG-III to induce PS [18] . The smoothing results are shown in Figures 14 and 15.…”

Research on characteristics of multidimensional polarization smoothing

“…Moreover, PS is relatively easy to achieve, typically, KDP or DKDP crystals or liquid crystal materials controlled by an electro-optical effect can both be used to realize PS. 11,14,15 In earlier research, the aforementioned birefringent elements were frequently arranged in parallel or convergent beam, and the transmission angles and paths of the ordinary wave and extraordinary wave were modified by using various wedge angles or incident light angles to produce two sets of separate speckle patterns with orthogonal polarization 10,15 . In this paper, a cascade of multiple birefringent elements is proposed to realize multidimensional polarization smoothing.…”

Heterogeneous growth of KDP/KT crystal

“…The KDP crystal is an irreplaceable multiplier material suitable for nonlinear optical switches, large-aperture highpower lasers, and frequency conversion in inertial confinement fusion (ICF) due to its adequate electro-optical coefficient and convenience in growing to as large as centimeter dimensions. [1][2][3][4] One of the most challenging tasks on KDP materials is the growth control since we can hardly study the exact mechanism of the growth process. It is expected that the atomic structure at the crystal-solution interface plays a primary role in the composition, growth, and morphology of the crystal due to the growth of crystal occurring at this boundary.…”