Rapid growth of a long-seed KDP crystal Download: 579次
1 Introduction
The high-power lasers used in the inertial confinement fusion (ICF) system worldwide need large KDP-type crystals as nonlinear crystals on account of their exceptional properties[1–6]. The major limitation to growing such large KDP-type crystals by the traditional method is the slow growth rate, leading to a growth cycle of 1–2 years[7–11]. Fortunately, the ‘point-seed’ rapid growth method was developed in the 1980s[12, 13]. For the KDP-type crystals produced by the ‘point-seed’ rapid growth method, all prismatic faces and pyramidal faces develop under high supersaturated solutions[14–17]. In addition, a pyramid–prism (PY–PR) boundary is generated when different kinds of crystallographic faces are sewn together[18–21]. By the orthogonal polarization interferometry technology,
In this study, a long-seed KDP crystal was rapidly grown. With almost the same high cutting efficiency to obtain THG-oriented samples, this long-seed KDP-type crystal can grow from a seed that is shorter than that of the cuboid KDP-type crystal. Then the crystalline quality, transmittance performance, laser-induced damage (LID) property and LID morphology of the long-seed KDP crystal were investigated.
2 Experimental setup
2.1 Crystal growth
The long-seed KDP crystal was rapidly grown in a self-developed 2000 L growth apparatus configured as an efficient continuous filtration system (CFS)[25, 26]. A long KDP seed with size
Fig. 1. Long-seed KDP crystal with size $471~\text{mm}\times 480~\text{mm}\times 400~\text{mm}$ .
2.2 Characterization techniques
To evaluate the properties of the long-seed KDP crystal, the high-resolution X-ray diffraction (HRXRD) of an X-cut sample from this crystal was carried out[29]. The transmission spectrum of a THG-oriented sample cut from the long-seed KDP crystal was tested using a Lambda 1050 spectrometer[18]. The LID threshold (LIDT) at 355 nm of the THG-oriented sample was investigated under a Nd:YAG laser[30]. The LID scattering image of the THG-oriented sample was captured by an online microscope system mounted on the laser damage facility, and the morphology of the LID bulk was observed by an offline polarization microscope[31].
3 Results and discussion
3.1 Advantages of cut THG-oriented samples
The THG-oriented samples cut from the cuboid KDP-type crystal and the long-seed KDP-type crystal are shown in Figure
For simplicity,
Therefore, to get 10 (
For the long-seed KDP-type crystal, the growth rate in the horizontal and vertical directions is approximately 3:2, according to the crystal grown in this study. Equations (
Therefore, to get 10 (
Fig. 2. THG-oriented samples cut from the cuboid KDP-type crystal (left) and the long-seed KDP-type crystal (right).
3.2 Crystalline quality of the long-seed KDP crystal
The HRXRD pattern of the (200) crystalline face cut from the long-seed KDP crystal is shown in Figure
3.3 Transmittance of the long-seed KDP crystal
The transmission spectrum of a THG-oriented sample of the long-seed KDP crystal is shown in Figure
3.4 Laser-induced damage property
The LID property at 355 nm of the THG-oriented sample cut from the long-seed KDP crystal is shown in Figure
Table 1. Fitting of different kinds of defects.
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A model is used to quantify the LID property of the long-seed KDP crystal[37, 38]. In Figure
3.5 Laser-induced damage morphology
Illuminated by a 532 nm probe laser, the LID scattering image of the THG-oriented sample is recorded by an online microscope system mounted on the laser damage facility. The microscope is placed orthogonally to the propagation direction of the 355 nm laser. Once the damage happens, the microscope immediately captures the LID scattering image. An LID scattering image at 30 J/cm2 (3 ns, 355 nm), is shown in Figure
The morphology of the damage points in Figure
4 Conclusions
Despite being the subject of study for more than 30 years, rapidly grown KDP-type crystals are still grown from a ‘point seed’. In this study, a long-seed KDP crystal with size
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Article Outline
Duanyang Chen, Bin Wang, Hu Wang, Xiangyu Zhu, Ziyuan Xu, Yuanan Zhao, Shenghao Wang, Kaizao Ni, Lili Zheng, Hui Zhang, Hongji Qi, Jianda Shao. Rapid growth of a long-seed KDP crystal[J]. High Power Laser Science and Engineering, 2020, 8(1): 010000e6.