Multiple pulse nanosecond laser induced damage study in LiB3O5 crystals.
ABSTRACT Multiple pulse nanosecond laser induced damage in the bulk of LiB3O5 (LBO) crystals was investigated at 1064 nm, 532 nm and 355 nm. Scanning electron microscopy of cleaved damage sites confirmed the presence of different zones that have already been reported in the case of KH2PO4 (KDP). Multi pulse measurements reveal a strong decrease of the damage threshold with increasing pulse number at 1064 nm (fatigue effect). A weaker fatigue effect was observed at 532 nm and no fatigue effect was found at 355 nm. This observation is best explained by an inherently statistical light matter interaction generating laser induced damage. Finally, a polarization dependent damage threshold anisotropy was evidenced at all three wavelengths, being strongest at 1064 nm. The results indicate the importance of Li+ vacancy stabilized color centers for the damage mechanism.
SourceAvailable from: Baoan Liu[Show abstract] [Hide abstract]
ABSTRACT: Three kinds of KH2PO4 raw material are used to grow deuterated potassium dihydrogen phosphate (DKDP) crystals by traditional and rapid growth methods, respectively. The growth habit dependence on the purity of raw material is described and analyzed. The optical properties including transmission spectra and laser- induced damage threshold of these crystals are measured. It is found that the growth method affects the optical properties of crystal more obviously than the raw material with the mass content of main metal ions below 1 ppm. Moreover, the morphology of the core in the observed damage sites indicates that an explosion process probably occurs during laser-induced breakdown.Chinese Optics Letters 09/2014; 12(10):101604. DOI:10.3788/COL201412.101604 · 1.07 Impact Factor
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ABSTRACT: Single point diamond turning (SPDT) currently is the leading finishing method for achieving ultra-smooth surface on brittle KH2PO4 crystal. In this work, the light intensification modulated by surface cracks introduced by SPDT cutting is numerically simulated using finite-difference time-domain algorithm. The results indicate that the light intensification caused by surface cracks is wavelength, crack geometry and position dependent. Under the irradiation of 355nm laser, lateral cracks on front surfaces and conical cracks on both front and rear surfaces can produce light intensification as high as hundreds of times, which is sufficient to trigger avalanche ionization and finally lower the laser damage resistance of crystal components. Furthermore, we experimentally tested the laser-induced damage thresholds (LIDTs) on both crack-free and flawed crystal surfaces. The results imply that brittle fracture with a series of surface cracks is the dominant source of laser damage initiation in crystal components. Due to the negative effect of surface cracks, the LIDT on KDP crystal surface could be sharply reduced from 7.85J/cm2 to 2.33J/cm2 (355nm, 6.4ns). In addition, the experiment of laser-induced damage growth is performed and the damage growth behavior agrees well with the simulation results of light intensification caused by surface cracks with increasing crack depths.Optics Express 11/2014; 22(23). DOI:10.1364/OE.22.028740 · 3.53 Impact Factor
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ABSTRACT: An imaging of strongly excited thin film dielectric coating is done by the means of femtosecond time-resolved off-axis digital holography (TRDH). Ta2O5 single layer coating have been investigated at different time moments in transmission mode. The evolving damage process was recorded in series of microscopic amplitude and phase contrast images. Different processes were found to occur and namely: Kerr effect, free-electron generation, ultrafast lattice heating and shock wave generation. The trends in electronic contribution are qualitatively reproduced by the theoretical model while the other effects require additional studies.SPIE Laser Damage; 11/2013