Effective absorption for thermal blooming due to aerosols

Chan, Chao-Wen

doi:10.1063/1.88003

Cited by 72 publications

(37 citation statements)

References 6 publications

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“…Due to a growth rate an order of magnitude faster than conventional growth, a greater number of bulk defects were formed, degrading the performance of the crystals by causing pinpoint damage and optical losses, which adversely affected the quality of the downstream beam [1,5] . It was found that typical damage pinpoints were caused by defects, which efficiently absorbed laser energy, leading to a temperature rise and subsequent 'micro-explosion' [5][6][7] . Various types of bulk defect, such as metallic impurities [8][9][10] , electronic defects [11][12][13] , organic materials, bacteria [14,15] , dislocation [16] and insoluble impurities, have been reported.…”

Section: Introductionmentioning

confidence: 99%

Performance of rapid-grown KDP crystals with continuous filtration

Wang

Chang

et al. 2015

High Pow Laser Sci Eng

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Rapid growth processing of KDP crystals was improved by employing continuous filtration to eliminate bulk defects. The performances of the KDP crystals, including scattering defects, laser damage resistance and transmittance, were measured and analyzed. Compared with rapid-grown KDP without continuous filtration, the transmittance in the nearinfrared was increased by at least 2%, almost all of 'micron size' defects were eliminated and 'sub-micron size' defects were decreased by approximately 90%. Laser damage testing revealed that the laser-induced damage thresholds (LIDTs), as well as the consistency of the LIDTs from sample to sample, were improved greatly. Moreover, it identified that 'micron size' defects were the precursors which initiated laser damage at relative lower laser fluence (4-6 J cm −2 ), and there was a lower correlation between smaller size scattering defects and laser damage initiation. The improved consistency in the LIDTs, attributed to elimination of 'micron size' defects, and LIDT enhancement originated from the decreased absorption of the KDP crystals.

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Section: Introductionmentioning

confidence: 99%

Performance of rapid-grown KDP crystals with continuous filtration

Wang

Chang

et al. 2015

High Pow Laser Sci Eng

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“…The nodule ejection is assumed to be initiated by laser energy absorption in the gold particle and spherical gold particle with a radius a = 125 nm embedded in an infinite homogeneous HfO 2 material. In the sphere symmetry coordinate, the temperature of the host material around the gold particle T can be calculated as [13,14] …”

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confidence: 99%

“…The thermal conductivity of the particle is much larger than that of the host material, so the temperature inside the particle can be assumed to be homogeneous. At the interface of the particle and the host, the power absorbed by the inclusion must be equal to the power leaving the surface by the conduction plus the rate of change in heat energy of the particle [13] …”

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confidence: 99%

Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Shan¹,

He²,

Wei³

et al. 2011

中国光学快报

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Samples with nodular defects grown from gold nanoparticles are prepared, and laser-induced damage tests are conducted on them. Nodular defects, which are in critical state of damage, are cross-sectioned by focusing on the ion beam and by imaging using a field emission scanning electron microscope. The crosssectional profile shows that cracks are generated and propagated along the nodular boundaries and the HfO2/SiO2 interface, or are even melted. The thermomechanical process induced by the heated seed region is analyzed based on the calculations of temperature increase and thermal stress. The numerical results give the critical temperature of the seed region and the thermal stress for crack generation, irradiated with threshold fluence. The numerical results are in good agreement with the experimental ones.OCIS Nodular defect, a typical defect in multilayer coatings, largely limits the improvement of the laser-induced damage threshold (LIDT) in the nanosecond regime and thus has been widely investigated. Electric field enhancement in the nodule, induced by the microlens effect of the dome structure of nodular defects, is an important factor in reducing the LIDT [1−5] . Recently, Liu et al. has examined the relationship between the structure feature of the nodular defect and the resistance of laserinduced damage (LID) [6−8] . Some simple thermal stress simulations and a simple thermo-mechanical model had been developed to understand the damage mechanism of the nodular defect [9−11] . The critical condition of crack generation regarded as a damage criterion and the corresponding LIDT were given based on the average temperature of the seed zone. However, the critical temperature of crack generation, the distribution of thermal stress, and the position of crack generation remain to be elucidated.Our previous work focused on investigating the characteristics and the electric field enhancement of nodular defects [12] . The geometric characteristics of nodular defect were determined by the seed. The height of the nodular dome and the continuity of the nodular boundary mainly determine the LIDT. The strong absorptive seed and microlens effect of the nodule play important roles in the LID of the nodule.In this letter, samples with nodular defects grown from gold nanoparticles were prepared, LID tests were performed. The thermomechanical process induced by the heated seed zone was analyzed. The morphology of a critically damaged nodule was analyzed with a double-beam microscope (Auriga, Zeiss, Germang) which combines the functions of the focused ion beam and the field emission scanning electron microscope (FESEM).The preparation of the samples, which are multilayer coatings with gold nanoparticles deposited on the surface of the substrate, and the details of the LID tests have been described in Ref. [12]. The total thickness of the coatings is about 4.0 µm, and the films are deposited by electron beam evaporation. The reflection coefficient of these samples is about 99% at 1 064 nm. The morphologies of nodule ejection ...

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“…The observed damage thresholds of KDP/DKDP crystals are much lower than the intrinsic thresholds [2]. It is now admitted that this damage is induced by point defects that efficiently absorb laser energy, inducing a fast temperature rise and a subsequent "micro-explosion" [3][4][5]. In order to ensure a good running of laser system, it is necessary to identify the nature of point defect and to understand the physical mechanism leading to laser damage.…”

Section: Introductionmentioning

confidence: 99%

“…(1) can be solved exactly for the given boundary conditions (i)-(iii). The final result for the temperature is given as [4]: Figure 11 displays the temperature of defect cluster in the time domain during and after laser exposure. The laser beam is characterized as a top hat 8ns pulse with the fluence of 10J/cm 2 .…”

mentioning

confidence: 99%

Transmittance increase after laser conditioning reveals absorption properties variation in DKDP crystals

Zhao

et al. 2012

Opt. Express

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By taking multiple measurements of transmittance before and after laser conditioning in DKDP crystals, we found that the transmittance was increased by 0.05%~0.4% through laser conditioning with maximum fluence 6J/cm 2 , and then decreased by about 0.1% after subsequent higher fluence conditioning. Variation of scattering intensity and absorber density, the two major factors leading to transmittance change, was monitored by on-line and off-line detection systems. The transmittance decrease was attributed to laser damage scattering, and the increase was derived from reduction of absorbers. Moreover, the absorption was reduced further at higher conditioning fluence. Based on the above analysis, the heating process during laser exposure was analyzed in the time domain, and a local rapid-rising and slow-cooling process was confirmed to reduce defect concentration, which can improve laser damage resistance and increase the transmittance.

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Effective absorption for thermal blooming due to aerosols

Cited by 72 publications

References 6 publications

Performance of rapid-grown KDP crystals with continuous filtration

Performance of rapid-grown KDP crystals with continuous filtration

Thermomechanical analysis of nodule damage in HfO2/SiO2 multilayer coatings

Transmittance increase after laser conditioning reveals absorption properties variation in DKDP crystals

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