Research on Nonlinear Absorption Effect in KDP and 70%-DKDP Crystals

Duanliang Wang,Jiyang Wang,Hui Liu,Pingping Huang,Robert Boughton,Chuanying Shen,Shenglai Wang,Weidong Li

doi:10.3390/cryst7070188

Duanliang Wang, Jiyang Wang + Show 6 more

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https://doi.org/10.3390/cryst7070188

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Abstract

Nonlinear optical absorption effect in KDP and 70%-DKDP crystals, which were grown by the conventional temperature cooling method, was systematically studied using picosecond pulse laser excitation. Using open aperture Z-scan measurements, the dependence of nonlinear absorption effect on sample orientations (I, II, and z) as well as laser intensity was systematically measured at λ = 1064 and 532 nm. According to the experimental results, the nonlinear absorption effect at λ = 532 nm was confirmed, while at λ = 1064 nm no nonlinear absorption was observed for KDP and 70%-DKDP crystals. In addition, the optical absorption along I- and II-type affected by laser intensity was larger than that along the z-direction. The important nonlinear absorption coefficients β and χ I ( 3 ) (esu) measured along different orientations were exhibited in detail at wavelengths of 1064 nm and 532 nm. The results indicate that nonlinear absorption coefficients increase first and then decrease with the increment of laser intensity for KDP and 70%-DKDP crystals.

Highlights

KH2 PO4 (KDP) and KD2−x Hx PO4 (DKDP) crystals, a kind of nonlinear optical material, find wide application as optical-electric conversion devices and multiple frequency converters [1,2,3,4]
One of the remarkable features is that the nonlinear absorption effects in KDP and 70%-DKDP crystals are clearly exhibited at λ = 532 nm, whereas there is no nonlinear absorption at λ = 1064 nm for a laser intensity less than 94 GW/cm2
The nonlinear absorption characteristics of KDP and 70%-DKDP crystals with different orientations and varying laser intensities have been systematically analyzed at λ = 1064 and 532 nm

Summary

Introduction

KH2 PO4 (KDP) and KD2−x Hx PO4 (DKDP) crystals, a kind of nonlinear optical material, find wide application as optical-electric conversion devices and multiple frequency converters [1,2,3,4]. They have wide applications in high-power laser systems, especially the Inertial Confinement Fusion system (ICF) [5,6]. Laser-induced damage, which results from the interaction of laser pulses with KDP or DKDP crystals, may be produced, which decreases laser conversion efficiency. A better understanding of nonlinear optical absorption properties is essential

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