A systematic error calibration method is presented to improve the measurement accuracy of lateral shearing interferometry (LSI). This method is used to remove the most significant errors: geometric optical path difference (OPD) and detector tilt error. Difference fronts in the 0° and 90° directions are used to reconstruct wavefront using difference Zernike polynomial fitting. And difference fronts in the 45° and 135° directions are also used to reconstruct wavefront. The coefficient differences between the reconstructed wavefront are generated from geometric OPD and detector tilt error. The relationship between Zernike coefficient differences and systematic parameters are presented based on shear matrix. Thus, the distance of diffracted light converging point (<i>d</i>) and detector tilt angle can be calculated from the coefficient difference. Based on the calculated <i>d</i> and detector tilt angle, the geometric OPD and detector-tilt induced systematic errors are removed and the measurement accuracy of LSI is improved.
The investigation of the influence polarization orientation on damage performance of type I doubler KDP crystals grown by the conventional growth method under under 532nm pulse exposure is carried out in this work. The obtained results point out the pinpoint density (ppd) of polarization parallels the extraordinary axis is around 1.5× less than that of polarization parallels the ordinary axis under the same fluence, although polarization has no influence on size distribution of pinpoints. Meanwhile, crystal inhomogeneity is observed during experiment.
A multipurpose laser damage test facility delivering pulses from 1ns to 20ns and designed to output energy 40 Joule at 351nm is presented. The laser induced damage threshold (LIDT) measurement and test procedure are performed. The original system consist of the online detection system based on the microscopy and an energy detection device based on the scientific grade Charge Coupled Device (CCD) which provides the method to measure the LIDT with high accuracy. This method is an efficient way that allows measuring a small area fluence which the defect exposed. After complete test procedure and data treatment the damage position of the defect has been found. Then we can obtain the local fluence of small area when the damage occurred. This procedure provides a straightforward means of laser-damage threshold obtained from the test method. Damage correlation of measures is discussed in connection with present theoretical understanding of laser damage phenomenon. The damage process in transparent dielectric materials being the results of complex processes involving multi-photon ionization, avalanche ionization, electron-phonon coupling, and thermal effects. Those complex processes lead to the damage on the optical surface. We performed a method to measure the local fluence which defects irradiated with high accurate.
For researching the influence factors of the damage threshold test results, the 1 on 1 test program and data processing on fused SiO2 optical elements was numerically simulated with Monte Carlo method. The influence of the surface defect density and the target test spots area for the test results of damage threshold was studied. The numerical simulation results indicate that the damage threshold of optical elements can't be accurately evaluated with 1 on 1 test program if the surface defects have the characteristics of both low density and low damage threshold. The zero-probability damage threshold isn't equal to the minimum energy density when the laser induced damage of optical element appears. This work is helpful for understanding the 1 on 1 test result and has important reference value in the actual damage threshold test of optical elements using 1 on 1 test method.
In this paper, we investigated the effects of laser pulse width on laser-induced damage. We measured the damage threshold of K9 glass
and UBK7 glass optical components at different pulse width, then analysis pulse-width dependence of damage threshold. It is shown
that damage threshold at different pulse width conforms to thermal restriction mechanism, Because of cm size laser beam, defect on
the optical component surface leads to laser-induced threshold decreased.