Study of the near-field modulation property of microwaviness on a KH2PO4 crystal surface |
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Authors: | Chen Ming-Jun Jiang Wei Li Ming-Quan and Chen Kuan-Neng |
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Affiliation: | Center for Precision Engineering,Harbin Institute of Technology,
Harbin 150001, China |
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Abstract: | The KH$_2$PO$_4$ crystal is a key component in optical systems of inertial
confinement fusion (ICF). The microwaviness on a KH$_2$PO$_4$ crystal
surface is strongly related to its damage threshold which is a key parameter
for application. To study the laser induced damage mechanism caused by
microwaviness, in this paper the near-field modulation properties of
microwaviness to the incident wave are discussed by the Fourier modal
method. Research results indicate that the microwaviness on the machined
surface will distort the incident wave and thus lead to non-uniform
distribution of the light intensity inside the crystal; in a common range of
microwaviness amplitude, the light intensity modulation degree increases
about 0.03 whenever the microwaviness amplitude increases 10~nm; 1
order diffraction efficiencies are the key factors responsible for light
intensity modulation inside the crystal; the light intensity modulation is
just around the microwaviness in the form of an evanescent wave, not inside the
crystal when the microwaviness period is below 0.712~$\mu $m; light intensity
modulation degree has two extreme points in microwaviness periods of
1.064~$\mu $m and 1.6~$\mu $m, remains unchanged between periods of 3~$\mu $m and 150~$\mu$m, and descends above the period of 150~$\mu $m to 920~$\mu $m. |
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Keywords: | KH2PO4 crystal laser induced damage threshold microwaviness Fourier modal method modulation degree |
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