Modeling laser conditioning of KDP crystals

Abstract

When potassium dihydrogen phosphate crystals (KH 2 PO 4 or KDP) are illuminated by multi-gigawatt nanosecond pulses, damages may appear in the crystal bulk. One can increase damage resistance through a conditioning that consists in carrying out a laser pre-exposure of the crystal. The present paper addresses the modeling of laserinduced conditioning of KDP crystals. The method is based on heating a distribution of defects, the cooperation of which may lead to a dramatic temperature rise. The conditioning is assumed to be due to a decrease in the defect absorption efficiency. Two scenarios associated with various defect natures are proposed and these account for certain of the observed experimental facts. For instance, in order to improve the crystal resistance to damage, one needs to use a conditioning pulse duration shorter than the testing pulse. Also, a conditioning scenario based on the migration of point (atomic-size) defects allows the reproduction of a logarithmic-like evolution of the conditioning gain with respect to the number of laser pre-exposures. Moreover, this study aims at refining the knowledge regarding the precursor defects responsible for the laser-induced damage in KDP crystals. Within the presented modeling, the best candidate permitting the reproduction of major experimental facts is comprised of a collection of one-hundred-nanometer structural defects associated with point defects as for instance cracks and couples of oxygen interstitials and vacancies.

Effect of UV Laser Conditioning on the Structure of KDP Crystal

“…And with the increase of laser fluence, smaller and smaller clusters are treated [17]. For the process of multiple-pulses conditioning, it may be understood with defect absorber model.…”

Initial Damage and Damage Growth of KDP Crystals Induced by 355 nm Pulse Laser

“…Many studies have shown that body defects introduced in the crystal growth step are the main reason for this induced bulk damage . Therefore, identification of KDP crystal body defects, and development of advanced growth and post processing techniques have been strongly researched in the materials field …”

“…[5,6] Therefore, identification of KDP crystal body defects, and development of advanced growth and post processing techniques have been strongly researched in the materials field. [7][8][9][10][11][12] In this paper, for the requirement of high fluence and long life operation of high power solid laser facility, the systematic research were carried out for the initial damage and damage growth behavior of KDP crystal induced by the ultraviolet pulse laser irradiation. We researched the effects of laser pulse energy on damage density and scattering loss KDP crystals, and analyzed micro-morphology characteristics of typical bulk damage.…”