High Power Laser Science and Engineering, (2019), Vol. 7, e46, 8 pages.
© The Author(s) 2019. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/
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doi:10.1017/hpl.2019.24
Rapid growth and properties of large-aperture
98%-deuterated DKDP crystals
Xumin Cai
1,2
, Xiuqing Lin
1
, Guohui Li
1
, Junye Lu
1
, Ziyu Hu
1,3
, and Guozong Zheng
1
1
Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou 350002, China
2
University of Chinese Academy of Sciences, Beijing 100049, China
3
College of Chemistry, Fuzhou University, Fuzhou 350116, China
(Received 12 March 2019; revised 22 April 2019; accepted 21 May 2019)
Abstract
In this paper, a highly deuterated potassium dihydrogen phosphate (DKDP) crystal with sizes up to 318 mm × 312 mm ×
265 mm was grown by the rapid-growth method. The synthesis tank device was specially designed to synthesize a higher
deuterium concentration and high-purity DKDP solution. The deuterium content of the as-grown crystal, which was
97.9%, was determined by two methods, including infrared (IR) spectroscopy and thermo-gravimetric analysis (TGA)
measurements. The performances of the 97.9% DKDP crystal, including transmission, absorption coefficient, and laser-
induced damage threshold (LIDT) were measured. The results indicate that, in the near-infrared band, the transmission
of the 97.9% DKDP crystal is higher than that of KDP and 70% DKDP crystals, and the absorption coefficient is lower.
The LIDT of the crystal reached 23.2 J · cm
−2
(R-on-1, 1064 nm, 3 ns), which meets the engineering requirements for
use in optical applications.
Keywords: DKDP crystal; large aperture; highly deuterated DKDP; rapid growth
1. Introduction
Deuterated potassium dihydrogen phosphate (DKDP) crys-
tals are optical materials with excellent properties, such as
high transmittance, high electro-optic coefficient and high
laser damage threshold, which are widely used for frequency
conversion and as electro-optical Q-switching crystals in
inertial confinement fusion (ICF) projects
[1–3]
. In particular,
DKDP crystals can grow to very large apertures, up to
900 mm by the water solution method
[2]
. Due to a hydrogen
atom being replaced by a deuterium atom, DKDP crys-
tals have a few differences in performance compared with
potassium dihydrogen phosphate (KDP) crystals, including
a weak stimulated Raman scattering (SRS) effect
[4–6]
and
a low half-wave control voltage, which is about half that
of KDP crystals
[7]
. As the number of deuterium atoms
increases, the electro-optic properties become better
[8]
. The
ICF project chooses large-aperture, highly deuterated DKDP
crystals as electro-optic switch materials
[9]
. However, the
growth of large-size, 98%-deuterated DKDP crystals faces
many difficulties, such as disturbance of the monoclinic
DKDP crystal during the growth of the tetragonal DKDP
Correspondence to: G. Zheng, 155 West Yangqiao Road, Fuzhou
350002, China. Email: zhengguozong@fjirsm.ac.cn
crystal, hydrogen–deuterium exchange, and the need for
expensive heavy water
[8, 10]
. To date, there have been very
few reports on the growth of highly deuterated DKDP
crystals.
The traditional temperature-reduction method for pro-
ducing crystals has been widely used to grow large-size,
highly deuterated DKDP crystals, which requires a long
period of more than one year
[2, 11, 12]
. It is difficult to
supply enough DKDP crystals by the traditional method,
so a rapid-growth technology is being urgently studied for
highly deuterated DKDP crystals. In 2014, Zhang et al.
[8]
reported that DKDP crystals with a deuterium content of
98% and sizes of 100 mm × 105 mm × 96 mm were suc-
cessfully grown by point-seed technology. The tetragonal-
to-monoclinic solubility transition can be avoided by the
rapid-growth technique
[10]
. It is essential that a rapid-growth
method is used for the growth of highly deuterated DKDP
crystals by the point-seed technique. The growth of large-
size, highly deuterated DKDP crystals is affected by many
factors
[10, 13]
, such as the need for highly pure raw mate-
rials, supersaturation stability, ultrafine filtration, the rate
of hydrogen–deuterium exchange, and the disturbance of
the monoclinic crystal. At present, large-scale, high-quality,
highly deuterated DKDP crystals are urgently needed for
1