Analysis of high resolution scatter images from laser damage experiments performed on KDP

Conference · Fri Jan 05 00:00:00 EST 1996

OSTI ID:192518

Runkel, M; Woods, B; Yan, M ^[1]

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1. and others

Interest in producing high damage threshold KH{sub 2}PO{sub 4} (KDP) and (D{sub x}H{sub 1-x}){sub 2}PO{sub 4} (KD*P, DKDP) for optical switching and frequency conversion applications is being driven by the system requirements for the National Ignition Facility (NIF) at Lawrence Livermore National Lab (LLNL). Historically, the path to achieving higher damage thresholds has been to improve the purity of crystal growth solutions. Application of advanced filtration technology has increased the damage threshold, but gives little insight into the actual mechanisms of laser damage. We have developed a laser scatter diagnostic to better study bulk defects and laser damage mechanisms in KDP and KD*P crystals. This diagnostic consists of a cavity doubled, kilohertz class, Nd:YLF laser (527 nm) and high dynamic range CCD camera which allows imaging of bulk scatter signals. With it, we have performed damage tests at 355 nm on four different {open_quotes}vintages{close_quotes} of KDP crystals, concentrating on crystals produced via fast growth methods. We compare the diagnostic`s resolution to LLNL`s standard damage detection method of 100X darkfield microscopy and discuss its impact on damage threshold determination. We have observed the disappearance of scatter sites upon exposure to subthreshold irradiation. In contrast, we have seen scatterers appear where none previously existed. This includes isolated, large (high signal) sites as well as multiple small scatter sites which appear at fluences above 7 J/cm{sup 2} (fine tracking). However, we have not observed a strong correlation of preexisting scatter sites and laser damage sites. We speculate on the connection between the laser-induced disappearance of scatter sites and the observed increase in damage threshold with laser conditioning.

• Research Organization: Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 192518
• Report Number(s): UCRL-JC-122321; CONF-9510309-3; ON: DE96005405; TRN: 96:008321
• Resource Relation: Conference: Symposium on optical materials for high power lasers, Orlando, FL (United States), 30 Oct - 1 Nov 1995; Other Information: PBD: 5 Jan 1996
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION
36 MATERIALS SCIENCE
42 ENGINEERING NOT INCLUDED IN OTHER CATEGORIES
LASER MATERIALS
DAMAGE
POTASSIUM COMPOUNDS
IMAGE PROCESSING
MATERIALS TESTING
OPTICAL SYSTEMS
LASER FUSION REACTORS
PHOSPHORUS OXIDES
INERTIAL CONFINEMENT
CRYSTAL GROWTH
THERMONUCLEAR REACTOR MATERIALS
DIAGNOSTIC TECHNIQUES
PHYSICAL RADIATION EFFECTS