Rapid growth of a long-seed KDP crystal

Abstract

To reduce the seed length while maintaining the advantages of the cuboid KDP-type crystal, a long-seed KDP crystal with size $471~\text{mm}\times 480~\text{mm}\times 400~\text{mm}$ is rapidly grown. With almost the same high cutting efficiency to obtain third harmonic generation oriented samples, this long-seed KDP-type crystal can be grown with a shorter seed than that of the cuboid KDP-type crystal. The full width at half maximum of the high-resolution X-ray diffraction of the (200) crystalline face is 28.8 arc seconds, indicating that the long-seed KDP crystal has good crystalline quality. In the wavelength range of 377–1022 nm, the transmittance of the long-seed KDP crystal is higher than 90%. The fluence for the 50% probability of laser-induced damage (LID) is $18.5~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm). Several test points survive when the laser fluence exceeds $30~\text{J}/\text{cm}^{2}$ (3 ns, 355 nm), indicating the good LID performance of the long-seed KDP crystal. At present, the growth of a long-seed DKDP crystal is under way.

Deep-UV optical properties of KDP-family crystals: a comprehensive characterization

“…The methods of growing KDP-family crystals mainly include the traditional temperature cooling technique and the "point seed" rapid growth technique 2,12,[24][25][26] . The traditional technique is to slowly reduce the solution temperature to obtain the driving force for crystal growth.…”

“…First, the growth solution needs to maintain high stability, and second, compared with the traditional technique, the optical qualities of the crystals obtained by the rapid growth technique decreased, such as the increase of internal light scattering and UV absorption, the decrease of optical homogeneity, and the reduction of laser damage threshold. At present, by studying the properties of KDP-family crystals under different growth conditions (including raw materials, growth methods, seed orientation, and deuterium content), the optimal growth process was determined and large-aperture and high-quality KDP-family crystals have been successfully obtained by both traditional method and rapid growth method 12,[27][28][29] . The single crystal optical devices with a size of >400 mm can be fabricated.…”

High-energy, high-repetition-rate ultraviolet pulses from an efficiency-enhanced, frequency-tripled laser

“…High-power ultraviolet (UV) lasers are desirable for many applications, including laser conditioning, micro-nano fabrication, laser-propelled space debris removal, quantum optics, and nonlinear optical measurement [1][2][3][4][5][6][7][8] . Owing to limitations in the emission spectra of gain crystals, high-power UV lasers are usually obtained by third harmonic generation (THG) from near-infrared lasers.…”

Potential damage threats to downstream optics caused by Gaussian mitigation pits on rear KDP surface

“…The issue of laser damage to potassium dihydrogen phosphate (KDP) crystal is an important factor restricting the development of high-power laser facilities for inertial confinement fusion (ICF) such as the National Ignition Facility (NIF) in the United States, the Laser MegaJoule in France and the Shenguang Laser Facility in China [1][2][3][4] . Laser damage sites on the surface of optical components would reduce their resistance to high power lasers, accelerate the scrapping of components and deteriorate the quality of laser beams [5,6] . For high-cost optics like KDP crystal, NIF proposed a 'recycling' strategy to mitigate the growth of laser-induced surface damage and maximize its lifetime [7,8] .…”