In this work, we investigate the laser-induced damage resistance at 355 nm in DKDP crystals grown with varying growth parameters, including temperature, speed of growth and impurity concentration. In order to perform this work, a DKDP crystal was grown over 34 days by the rapid-growth technique with varied growth conditions. By using the same crystal, we are able to isolate growth-related parameters affecting LID from raw material or other variations that are encountered when testing in different crystals. The objective is to find correlations of damage performance to growth conditions and reveal the key parameters for achieving DKDP material in which the number of damage initiating defects is reduced. This approach can lead to reliable and expedite information regarding the importance of different crystal growth parameters on the laser damage characteristics of these crystals

DeMange, P

Demos, S G

Negres, R A

Zaitseva, N P

UNT Digital Library

UCRL-PROC-225780A new expedited approach to evaluatethe importance of different crystal growthparameters on laser damageperformance in KDP and DKDPR. A. Negres, N. P. Zaitseva, P. DeMange, S. G.DemosNovember 1, 2006Boulder Damage SymposiumBoulder, CO, United StatesSeptember 25, 2006 through September 27, 2006Disclaimer   This document was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor the University of California nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or the University of California. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or the University of California, and shall not be used for advertising or product endorsement purposes.  A new expedited approach to evaluate the importance of differentcrystal growth parameters on the laser damage performance inKDP and DKDPR. A. Negres, N. P. Zaitseva, P. DeMange, and S. G. DemosLawrence Livermore National Laboratory7000 East Avenue, Livermore, CA 94551, USAABSTRACTIn this work, we investigate the laser-induced damage resistance at 355 nm in DKDP crystals grown with varying growthparameters, including temperature, speed of growth and impurity concentration. In order to perform this work, a DKDPcrystal was grown over 34 days by the rapid-growth technique with varied growth conditions. By using the same crystal,we are able to isolate growth-related parameters affecting LID from raw material or other variations that are encounteredwhen testing in different crystals. The objective is to find correlations of damage performance to growth conditions andreveal the key parameters for achieving DKDP material in which the number of damage initiating defects is reduced. Thisapproach can lead to reliable and expedite information regarding the importance of different crystal growth parameterson the laser damage characteristics of these crystals.Keywords: Laser-induced damage, KDP and DKDP crystals, crystal growth1. INTRODUCTIONOur knowledge on how to improve the laser damage resistance of KDP and DKDP crystals still remains very limited.Localized damage initiation in KDP has been attributed to either impurity nanoparticles incorporated during growthor clusters of intrinsic material defects that form during growth.1–3 However, the precise nature of these defects andthe growth parameters affecting their concentrations have not yet been identified. Extensive past work has focusedon measuring the damage threshold (DT) in crystals that were grown under different conditions including impuritycontent, speed of growth, growth temperature, etc.4–8 However, the variation in DTs observed even from crystals grownunder presumed ”identical” conditions along with the probabilistic nature of the DT measurement resulted in a difficultyto obtain reproducible experimental results which in turn led to extensive and labor intensive efforts. Arguably, afundamental improvement in the damage characteristics of these materials may require the development of techniquesthat can offer reliable and expedited information regarding the role of the different growth conditions on the ultimatedamage performance of the material.In this work, we explore a novel approach to addressing laser-induced damage (LID) in KDP/DKDP crystals bymeans of controlled crystal growth. The objective is to acquire a basic understanding on how growth parameters affectthe damage performance of these materials and devise methods to eliminate or passivate the damage precursors. Theoriginal rapid-growth technique used for growth of large-aperture KDP crystals for National Ignition Facility is anexcellent tool for scientific investigations, offering the advantage of a precise control of temperature, supersaturation,growth rate, hydrodynamic flow, etc.9 This technique was employed to grow a small DKDP crystal with varied growthconditions. Newly developed diagnostic tools provided high resolution, quantitative assessment of damage resistancefrom various sectors and regions of the crystal.102. EXPERIMENTThis study has been enabled by the development of a new damage testing system where the bulk damage density (pinpointdensity or PPD) is directly measured as a function of exposure laser fluence to obtain the damage density profile (notonly DT). The experimental setup along with the system capabilities have been described in detail elsewhere.10 In brief,damage testing is performed with the third harmonic (355-nm) of a ∼ 3-ns pulsed Nd:YAG laser focused by a 200-mmfocal length cylindrical lens in the bulk of the crystal samples. Scattered light images of each volume are capturedorthogonally to the laser propagation direction and the damage pinpoint density is measured over the region of thecrystal exposed to only peak laser fluence.Send correspondence to R. A. Negres: E-mail: negres2@llnl.gov Figure 1. Growth history of a small DKDP crystal grown by the rapid-growth method with varied growth conditions: height ofthe boule (in mm) and growth temperature (in ◦C) vs. time (in days).To perform this work, a DKDP crystal was grown over 34 days by the rapid-growth technique with varied growthconditions over a very wide range.9 The height of the boule, including the seed (∼10 mm), along with the solutiontemperature were recorded daily and are illustrated in Fig. 1 (the horizontal distance from the seed was also recordedbut it is not shown here). The growth history includes three distinct stages: i) initial growth at constant temperatureof 58 ◦C with a gradual decreasing growth rate from 21 mm/day to ≤ 1 mm/day (during the first 4 days), ii) constant,slow growth rate close to that used in conventional crystal growth by a slow decrease of the temperature from 58 ◦C to50 ◦C (during 29 days), and iii) increasing speed of growth by a rapid reduction of temperature down to 30 ◦C (duringday 34). A Y-cut plate (1-cm thick) was then obtained from this crystal boule and polished on all sides. Furthermore,three smaller samples were cut as depicted in Fig. 2 in order to facilitate their positioning in the damage testing system.The final transverse dimensions of the plate are shown in Fig. 2 along with the average growth rates (in mm/day) andthe locations of the boundaries between growth sectors and different speed of growth regions. The slow growth region(referred to as ‘the dead zone’) is delimited by the solid lines parallel to the crystal faces. The dotted line (drawn in theleft-hand side of the plate) indicates the boundary between prismatic (lower) and pyramidal (upper) sectors. Hence, thethree samples contained the two distinct growth sectors (pyramidal and prismatic), each sector including material grownat different growth rates from the early or the late stages of growth. Figure 2. Illustration of the crystal growth map in a DKDP plate obtained from the boule grown with varied growth rates.Damage testing locations are also shown [line-outs, locations (a)–(d) and 1–3].3. RESULTS AND DISCUSSIONDamage testing at 355 nm was performed at the locations shown in Fig. 2, representative of the various growth regions.For example, locations 1, 2, and 3 were chosen in the vicinity of the sector boundary within the late, fast growth material(prismatic, sector boundary and pyramidal, respectively) to provide information on the damage behavior at the sectorboundary. In this case, damage testing was performed with a single pulse at a fixed fluence (∼21 J/cm2) and scatteredlight images were acquired. Figure 3 illustrates the damage density from each tested volume at locations 1, 2, and 3 (forcomparison, same contrast is used in all images). The images reveal a dramatic enhancement (up to 10×) in the damagedensity at the sector boundary as compared to that observed from prismatic and/or pyramidal material grown at similargrowth rate. It should be noted that the region with enhanced damage can spread as far as 10 mm on either side of thegeometrical sector boundary (i.e., the intersection of the pyramidal {101} and prismatic {100} faces).312Figure 3. Scattered light images (same contrast) of damaged volumes at locations 1, 2, and 3 (see Fig. 2) following damagetesting with single pulse at fixed fluence of ∼21 J/cm2.In order to compare the damage characteristics of the two sectors as well as late vs early growth material, we havetested at four locations (a)–(d) (shown in Fig. 2) which represent material grown at fast average rates of 19-21 mm/day.(I) (II)Figure 4. Damage density profiles at 355 nm obtained from various locations (see Fig. 2) within early and late growth materialof prismatic and pyramidal sectors for two growth rates, 19-21mm/day and 8 mm/day [(I) and (II), respectively].Figure 4(I) illustrates typical damage profiles obtained at the aforementioned locations. It is known that the two sectorsof the crystal have very different distribution of impurities that incorporate during growth.7 This effect is most pronouncedwhen comparing early growth prismatic and pyramidal material (in the late growth material, depletion of the solutionis responsible for the lower concentration of impurities found in the two sectors). These results show that pyramidaland prismatic sectors exhibit identical damage behavior, in either early [locations (a) and (c)] or late growth material[locations (b) and (d)] and demonstrate that LID is independent of impurity concentration. Moreover, the damageresistance of late growth material (grown at ∼30 ◦C) is greatly improved over that from early growth material (formedat higher temperature), in both sectors. Given that the rate of growth was constant at the four locations, we concludethat the lower growth temperature is a key parameter in achieving better damage performance. These observations arein agreement with suggestions from previous work based on DT measurements.6–8, 11 Similar trends in damage behaviorswere assessed at a lower growth rate of 8 mm/day [see Fig. 4(II)], by testing in the corresponding regions prior to andafter ‘the dead zone’ (locations are not labelled in Fig. 2).The changing speed of growth throughout this boule provides the means to investigate the dependence of damage ongrowth rate, i.e. by recording the damage density after damage testing at a fixed fluence along the line-outs illustrated inFig. 2 as a function of position. Results from damage testing at 6.5 J/cm2, 8.3 J/cm2 and 10.5 J/cm2 along a horizontalline within the prismatic sector (shown in Fig. 2) are presented in the top panel of Fig. 5. The speed of growth andgrowth temperature corresponding to various locations can be inferred from the growth history of the boule, as illustratedin the middle panel of Fig. 5. UV absorption was also performed along the same horizontal line in the prismatic sector02004006008001000120010 20 30 40 50 60 70  Deadzone  10.5 J/cm2 8.3 J/cm2 6.5 J/cm2Pinpoints per mm3051015202530354045505560 Growth rateGrowth (mm/day)  Growth tempTemperature (deg)10 20 30 40 50 60 700.20.40.8  Absorption Horizontal distance from seed (mm) 270 nm 353 nmPrismFigure 5. (Top panel) Damage pinpoint density after testing at 355-nm at fixed fluences of 6.5 J/cm2, 8.3 J/cm2 and 10.5J/cm2 along a horizontal line within the prismatic sector (location shown in Fig. 2) as a function of distance from the seed. Thecorresponding growth rates and temperatures, as well as UV absorption are also shown (middle and bottom panels, respectively).and is presented in the bottom panel of Fig. Fig. 5. Several conclusions can be drawn from Fig. 5: i) damage resistanceis fairly independent of the growth rate in early, constant temperature (58 ◦C ) grown material (i.e., at locations up to35 mm away from the seed); ii) inside the dead zone and beyond, the damage performance is improved at higher growthrates in connection to lower growth temperatures; iii) sudden increase in the damage density occurs in the vicinity ofgrowth boundaries (i.e., located at ∼45 mm and ∼55 mm from the seed), similar to that observed at sector boundary (inaddition, small increases in damage density at locations 15 and 25 mm from the seed may be due to vicinal sectoriality);iv) UV absorption measurements also reveal the precise location of the growth boundaries but no correlation betweenabsorption and LID from various regions exists, in agreement with previous studies.7 Damage testing at fixed fluenceswas also performed along a vertical line-out (indicated in Fig. 2) crossing the sector boundary in early growth materialand the results are consistent with the conclusions outlined in this section (not shown here).4. SUMMARYThe results obtained in this proof-of-principle experimental work provide strong evidence that this approach is valid.Specifically, within this single experiment, we were able to reproduce and confirm results from earlier reports (e.g., thedependence of damage performance on growth temperature and non correlation with impurity concentration) as wellas reveal new relationships previously not addressed. Namely, i) at constant growth temperature, damage resistancein DKDP is independent of growth rate; ii) growth and vicinal boundaries formed due to abrupt changes in growthconditions, similar to sector boundaries, lead to dramatically enhanced damage and thus require special attention.ACKNOWLEDGMENTSThis work was performed under the auspices of the U.S. Department of Energy by University of California, LawrenceLivermore National Laboratory under contract no. W-7405-Eng-48.REFERENCES1. R. W. Hopper and D. Uhlmann, “Mechanism of inclusion damage in laser glass,” J. Appl. Phys. 41, pp. 4023–, 1970.2. M. D. Feit and A. M. Rubenchik, “Implications of nanoabsorber initiators for damage probability curves, pulselengthscaling and laser conditioning,” in Laser-Induced Damage in Optical Materials, G. J. Exarhos, A. H. Guenther,N. Kaiser, K. L. Lewis, M. J. Soileau, and C. J. Stolz, eds., Proc. SPIE 5273, pp. 74–82, 2003.3. C. W. Carr, H. B. Radousky, and S. G. Demos, “The wavelength dependence of laser induced damage: Determiningthe damage initiation mechanisms,” Phys. Rev. Lett. 91, p. 127402, 2003.4. H. Endert and M. L. Martin, “The effect of chromium impurities on the laser damage thresholds of KDP crystals,”Cryst. Res. Technol. 16, pp. K65–K66, 1981.5. H. Endert and W. Melle, “Laser-induced damage in KDP crystals,” Phys. Status Solidi 74, pp. 141–148, 1982.6. M. J. Runkel, B. W. Woods, M. Yan, J. J. De Yoreo, and M. R. Kozlowski, “Analysis of high-resolution scatterimages from laser damage experiments performed on KDP,” in Laser-Induced Damage in Optical Materials, H. E.Bennett, A. H. Guenther, M. R. Kozlowski, B. E. Newman, and M. J. Soileau, eds., Proc. SPIE 2714, pp. 185–195,1996.7. M. Yan, R. A. Torres, M. J. Runkel, B. W. Woods, I. D. Hutcheon, N. P. Zaitseva, and J. J. De Yoreo, “Investigationof impurities and laser-induced damage in the growth sectors of rapidly grown KDP crystals,” in Laser-InducedDamage in Optical Materials, H. E. Bennett, A. H. Guenther, M. R. Kozlowski, B. E. Newman, and M. J. Soileau,eds., Proc. SPIE 2966, pp. 11–16, 1997.8. A. K. Burnham, M. Runkel, M. D. Feit, A. M. Rubenchik, R. L. Floyd, T. A. Land, W. J. Siekhaus, and R. A.Hawley-Fedder, “Laser-induced damage in deuterated potassium dihydrogen phosphate,” Appl. Opt. 42, pp. 5483–5495, 2003.9. N. Zaitseva and L. Carman, “Rapid growth of KDP-type crystals,” Progr. Cryst. Growth Ch. 43, pp. 1–118, 2001.10. P. DeMange, C. W. Carr, H. B. Radousky, and S. G. Demos, “System for evaluation of laser-induced damageperformance of optical materials for large aperture lasers,” Rev. Sci. Instrum. 75, pp. 3298–3301, 2004.11. A. K. Burnham, M. Runkel, R. A. Hawley-Fedder, M. L. Carman, R. A. Torres, and P. K. Whitman, “Low-temperature growth of DKDP for improving laser-induced damage resistance at 350 nm,” in Laser-Induced Damagein Optical Materials, G. J. Exarhos, A. H. Guenther, M. R. Kozlowski, K. L. Lewis, and M. J. Soileau, eds., Proc.SPIE 4347, pp. 373–382, 2001.

A new expedited approach to evaluate the importance of different crystal growth parameters on laser damage performance in KDP and DKDP

https://digital.library.unt.edu/ark:/67531/metadc880447/m2/1/high_res_d/896619.pdf

A new expedited approach to evaluate the importance of different crystal growth parameters on laser damage performance in KDP and DKDP

Abstract

Similar works

Full text

Available Versions

UNT Digital Library